Biodegradation

J Chromatogr A, 1999 Jul 23, 849(2), 371 - 80
Improvement in the Iatroscan thin-layer chromatographic-flame ionisation detection analysis of marine lipids . Separation and quantitation of monoacylglycerols and diacylglycerols in standards and natural samples; Striby L et al.; Mono- and diacylglycerols are important intermediates in glycerolipid biodegradation and intracellular signalling pathways . A method for mass determination of these lipid classes in marine particles was developed using the Iatroscan, which combines thin layer chromatography (TLC) and flame ionisation detection (FID) techniques . We improved existing protocols by adding two elution steps: hexane-diethyl-ether-formic acid (70:30:0.2, v/v/v) after triacylglycerol and free fatty acid scan, and acetone 100% followed by chloroform-acetone-formic acid (99:1:0.2, v/v/v) after 1,2 diacylglycerols . Diacylglycerol isomers 1,2 and 1,3 were separated from each other, as well as from free sterols in standards and marine lipids from sediment trap particles . Monoacylglycerols were separated from pigments and galactosyl-lipids in the same trap samples and in a rich pigment phytoplankton extract of Dunaliella viridis . Quantitation of each class in samples was performed after calibration with 0.5 to 2 micrograms of standards . As many as 17 lipid classes can be identified and quantified in samples using this proposed six-step development.

Can J Microbiol, 1999 Jun, 45(6), 520 - 9
Cross-induction of pyrene and phenanthrene in a Mycobacterium sp . isolated from polycyclic aromatic hydrocarbon contaminated river sediments; Molina M et al.; A polycyclic aromatic hydrocarbon (PAH)-degrading culture enriched from contaminated river sediments and a Mycobacterium sp . isolated from the enrichment were tested to investigate the possible synergistic and antagonistic interactions affecting the degradation of pyrene in the presence of low molecular weight PAHs . The Mycobacterium sp . was able to mineralize 63% of the added pyrene when it was present as a sole source of carbon and energy . When the enrichment culture and the isolated bacterium were exposed to phenanthrene, de novo protein synthesis was not required for the rapid mineralization of pyrene, which reached 52% in chloramphenicol-treated cultures and 44% in the absence of the protein inhibitor . In the presence of chloramphenicol, < 1% of the added pyrene was mineralized by the mixed culture after exposure to anthracene and naphthalene . These compounds did not inhibit pyrene utilization when present at the same time as pyrene . Concurrent mineralization of pyrene and phenanthrene after exposure to either compound was observed . Cross-acclimation between ring classes of PAHs may be a potentially important interaction influencing the biodegradation of aromatic compounds in contaminated environments.

Cytometry, 1999 Sep 1, 37(1), 14 - 20
Correlating cell cycle with metabolism in single cells: combination of image and metabolic cytometry; Krylov SN et al.; BACKGROUND: We coin two terms: First, chemical cytometry describes the use of high-sensitivity chemical analysis techniques to study single cells . Second, metabolic cytometry is a form of chemical cytometry that monitors a cascade of biosynthetic and biodegradation products generated in a single cell . In this paper, we describe the combination of metabolic cytometry with image cytometry to correlate oligosaccharide metabolic activity with cell cycle . We use this technique to measure DNA ploidy, the uptake of a fluorescent disaccharide, and the amount of metabolic products in a single cell . METHODS: A colon adenocarcinoma cell line (HT29) was incubated with a fluorescent disaccharide, which was taken up by the cells and converted into a series of biosynthetic and biodegradation products . The cells were also treated with YOYO-3 and Hoechst 33342 . The YOYO-3 signal was used as a live-dead assay, while the Hoechst 33342 signal was used to estimate the ploidy of live cells by fluorescence image cytometry . After ploidy analysis, a cell was injected into a fused-silica capillary, where the cell was lysed . Fluorescent metabolic products were then separated by capillary electrophoresis and detected by laser-induced fluorescence . RESULTS: Substrate uptake measured with metabolic cytometry gave rise to results similar to those measured by use of laser scanning confocal microscopy . The DNA ploidy histogram obtained with our simple image cytometry technique was similar to that obtained using flow cytometry . The cells in the G(1) phase did not show any biosynthetic activity in respect to the substrate . Several groups of cells with unique biosynthetic patterns were distinguished within G(2)/M cells . CONCLUSIONS: This is the first report that combined metabolic and image cytometry to correlate formation of metabolic products with cell cycle . A complete enzymatic cascade is monitored on a cell-by-cell basis and correlated with cell cycle .

J Biomed Mater Res, 1999 Nov, 47(2), 270 - 7
Characterization and biocompatibility of epoxy-crosslinked dermal sheep collagens; van Wachem PB et al.; Dermal sheep collagen (DSC), which was crosslinked with 1, 4-butanediol diglycidyl ether (BD) by using four different conditions, was characterized and its biocompatibility was evaluated after subcutaneous implantation in rats . Crosslinking at pH 9.0 (BD90) or with successive epoxy and carbodiimide steps (BD45EN) resulted in a large increase in the shrinkage temperature (T(s)) in combination with a clear reduction in amines . Crosslinking at pH 4.5 (BD45) increased the T(s) of the material but hardly reduced the number of amines . Acylation (BD45HAc) showed the largest reduction in amines in combination with the lowest T(s) . An evaluation of the implants showed that BD45, BD90, and BD45EN were biocompatible . A high influx of polymorphonuclear cells and macrophages was observed for BD45HAc, but this subsided at day 5 . At week 6 the BD45 had completely degraded and BD45HAc was remarkably reduced in size, while BD45EN showed a clear size reduction of the outer DSC bundles; BD90 showed none of these features . This agreed with the observed degree of macrophage accumulation and giant cell formation . None of the materials calcified . For the purpose of soft tissue replacement, BD90 was defined as the material of choice because it combined biocompatibility, low cellular ingrowth, low biodegradation, and the absence of calcification with fibroblast ingrowth and new collagen formation .

Can J Microbiol, 1999 May, 45(5), 377 - 88
Microbial mineralization of diisopropanolamine; Gieg LM et al.; Diisopropanolamine (DIPA) is a "sweetening agent" used to remove hydrogen sulfide from sour natural gas, and it is a contaminant at some sour gas treatment facilities in western Canada . To investigate the biodegradation of this alkanolamine, 14C-DIPA was used in anaerobic and aerobic mineralization studies . Between 3 and 78% of the radioactivity from this compound was released as 14CO2 in sediment-enrichment cultures incubated under nitrate-reducing conditions . Similarly, 12-78% of the label was converted to 14CO2 in sediment-enrichment cultures incubated under Mn(IV)-reducing conditions . These activities were observed at 8 degrees C, a typical groundwater temperature in western Canada, and at 28 degrees C . In contrast, DIPA-degrading activity was difficult to sustain under Fe(III)-reducing conditions, and < 25% of the radioactive label from 14C-DIPA was liberated as 14CO2 . Two mixed cultures and two isolates (both irregular, non-sporeforming, Gram-positive rods) were used to assess aerobic mineralization of 14C-DIPA . The aerobic mixed cultures released 73 and 79% of the radioactive label as 14CO2, whereas the pure cultures liberated only 39 and 47% as 14CO2 . Between one-third and one-half of the nitrogen from DIPA was found as ammonium-N in aerobic batch cultures . These results clearly demonstrate that DIPA is mineralized under a variety of incubation conditions.

Can J Microbiol, 1999 May, 45(5), 360 - 8
Biodegradation of benzothiophene sulfones by a filamentous bacterium; Bressler DC et al.; Previous studies showed that benzothiophene and 3- and 5-methylbenzothiophenes are oxidized by some bacteria to yield their corresponding sulfones, which were not subsequently degraded . In this study, a filamentous bacterium was isolated, which grew on each of these three sulfones as its sole carbon, sulfur, and energy source . Based on 16S rRNA gene sequencing and scanning electron microscopy, the isolate was found to belong to the genus Pseudonocardia and assigned the strain designation DB1 . Benzothiophene sulfone and 3-methylbenzothiophene sulfone were more readily biodegraded than 5-methylbenzothiophene sulfone, and growth on these three compounds resulted in the release of 57, 62, and 28% of the substrate carbon as CO2, respectively . The thiophene ring was also cleaved, and between 44 and 88% of the sulfur from the consumed substrate was found as sulfate and (or) sulfite . Strain DB1 grew on benzoate, dibenzothiophene sulfone, and hexadecanoic acid, but it could not grow on benzofuran, dibenzothiophene, dibenzothiophene sulfoxide, hexadecane, indole, naphthalene, phenol, 2-sulfobenzoic acid, sulfolane, benzothiophene, or 3- or 5-methylbenzothiophenes . In addition, it did not oxidize the latter three compounds to their sulfones.

Microb Ecol, 1999 Aug, 38(2), 114 - 125
Occurrence of Two Resin Acid-Degrading Bacteria and a Gene Encoding Resin Acid Biodegradation in Pulp and Paper Mill Effluent Biotreatment Systems Assayed by PCR; Yu Z et al.; > Abstract We examined the distribution of two dehydroabietic acid-degrading bacteria, Pseudomonas abietaniphila BKME-9 and Zoogloea resiniphila DhA-35, in biotreatment systems for pulp and paper mill effluents (PPMEs) using PCR assays . These two bacteria were first isolated from two PPME biotreatment systems and can degrade both dehydroabietic acid (DhA) and other abietane resin acids . We also examined the distribution of a catabolic gene, ditA1, encoding the alpha subunit of an aromatic ring-hydroxylating dioxygenase involved in DhA degradation by BKME-9 . PCR primers specific for the 16S rDNA of BKME-9 and of DhA-35 and specific for ditA1 were used . Among 3 laboratory- and 17 full-scale PPME biotreatment systems, 10 contained phylotype BKME-9, 3 contained phylotype DhA-35, and 11 contained ditA1, indicating the wider distribution of phylotype BKME-9 than of phylotype DhA-35 . Both phylotype BKME-9 and ditA1 were detected in the biotreatment system from which BKME-9 was originally isolated in 1994, suggesting the persistance of BKME-9 in that biotreatment system . The detection limit of the PCR assay was one cell per PCR reaction, which corresponds to one BKME-9 cell per 6 x 10(7) total sludge bacteria . A competitive PCR assay indicated that ditA1 ranged from 51 to 250 copies/mg of dry biomass . BKME-9 appears to contribute to the biodegration of resin acids in some PPME biotreatment systems . Using degenerate PCR primers and touchdown PCR, we obtained from our DhA-degrading strain collection six DNA sequences putatively homologous to that of ditA1 . Cluster analysis of these DNA sequences suggests that ditA1 encodes a representative of a novel class of dioxygenase enzymes.http://link.springer-ny.com/link/service/journals/00248/bibs/38n2p114.html

Fungal Genet Biol, 1999 Jul-Aug, 27(2-3), 175 - 85
Biodegradation of lignin by white rot fungi; Leonowicz A et al.; A review is presented related to the biochemistry of lignocellulose transformation . The biodegradation of wood constituents is currently understood as a multienzymatic process with the mediation of small molecules; therefore, this review will focus on the roles of these small molecular compounds and radicals working in concert with enzymes . Wood rotting basidiomycetous fungi penetrate wood and lead to more easily metabolized, carbohydrate constituents of the complex . Having a versatile machinery of enzymes, the white rot fungi are able to attack directly the "lignin barrier." They also use a multienzyme system including so-called "feed back" type enzymes, allowing for simultaneous transformation of both lignin and cellulose . These enzymes may function separately or cooperatively .

J Dent Res, 1999 Aug, 78(8), 1459 - 68
Biodegradation of commercial dental composites by cholesterol esterase; Santerre JP et al.; The research literature suggests that current dental polymeric composites are not chemically inert at the material/biological interface . Several studies have investigated the process of "biodegradation" on dental composites in the presence of enzymes, by monitoring changes in weight loss and surface hardness properties . However, it is hypothesized that these methods can provide an erroneous measure of biochemically induced degradation, since they are less sensitive to molecular events and lack the ability to provide chemical information . Knowledge of the latter is important because it relates to the biological significance of biodegradation, i.e., the identification and quantification of released compounds that may be capable of influencing cell, bacteria, or enzyme function . It was the objective of this study to compare three methods (weight loss, surface micro-hardness, and liquid chromatography combined with mass spectrometry) for their ability to measure the effect of enzyme-induced biodegradation on three commercial composite resin materials . The enzyme was cholesterol esterase, and the composites were Silux Plus XL, Z100 A2 (3M), and TPH XL (L.D . Caulk) . Biodegradation was readily detected by liquid chromatography, and its sensitivity was shown to be substantially greater than that of weight loss or surface hardness measurements, although surface hardness measurements did show some agreement with liquid chromatography data . The data also indicated that the levels and distribution of released degradation products can vary substantially from one product to the next, and that this merits further investigation if the potential impact of different commercial restorative materials on cell and bacteria function is to be assessed.

Biomed Mater Eng, 1999, 9(1), 49 - 59
Preparation and characterization of Japanese encephalitis virus vaccine loaded poly(L-lactide-co-glycolide) microspheres for oral immunization; Khang G et al.; Japanese encephalitis virus (JEV) vaccine loaded biodegradable poly(L-lactide-co-glycolide) (PLGA) microspheres (MSs) were prepared by W/O/W solvent evaporation method to study the possibility for oral vaccination . The influence of several preparation parameters as stirring rate, types and concentration of emulsifier, PLGA concentration, etc . has been observed on size, size distribution and biodegradation . The mean MSs size decreased when the agitation speed and the concentration of emulsifier were increased, and when the PLGA concentration was decreased . The surface morphology of porous and nonporous JEV vaccine loaded PLGA MSs was prepared from polyvinylalcohol and sodium dodecyl sulfate as used emulsifiers, respectively . From the assay of lactic acid and scanning electron microscope observation, it can be suggested that the rate of biodegradation of nonporous MSs was slower than that of porous surface morphology due to lower the surface area . Mechanisms of the formation of porous and nonporous surface by different types of emulsifier, and the biodegradation of MSs have been proposed . Also, the size and size distribution of JEV vaccine loaded PLGA MSs were discussed to apply oral vaccination through the Peyer's patches across the gastrointestinal tract.

FEMS Microbiol Lett, 1999 Jul 15, 176(2), 477 - 82
Metabolism of phenylbenzoate by Pseudomonas sp . strain TR3; Reich T et al.; A bacterial isolate, tentatively identified as Pseudomonas sp . strain TR3, was found to utilize the diaryl ester phenylbenzoate as sole source of carbon and energy . This strain has the ability to productively degrade phenylbenzoate and some substituted derivatives by a catabolic sequence which was characterized biochemically . The biodegradation of phenylbenzoate is thus initiated by an inducible esterase, effectively hydrolyzing the diaryl esters to produce stoichiometric amounts of two monoaromatic metabolites, identified as benzoate and phenol in the case of phenylbenzoate . The diaryl ester p-tolylbenzoate was hydrolyzed to yield benzoate and 4-methylphenol while 4-chlorophenylbenzoate gave rise to the production of benzoate and 4-chlorophenol . These monoaromatic catabolites were further degraded via the oxoadipate pathway.

J Biomater Sci Polym Ed, 1999, 10(7), 729 - 49
Commercial polyurethanes: the potential influence of auxiliary chemicals on the biodegradation process; Vermette P et al.; This investigation elucidates some aspects of auxiliary chemicals on the biodegradation of two commercial polyurethanes (Pellethane and Corethane) . The materials were incubated for 28 days with cholesterol esterase and/or with phosphatidylcholine . Extraction studies were carried out on the two materials, using different solvents, chosen on the basis of solvent polarity . FT-IR spectra for the extracted materials indicated the presence of poly(methylene)n oxide moities, silicone oil, bis-ethylene-stearamide, aromatic moities, and alkyd-urea compounds in Pellethane . Corethane materials were shown to contain some fatty acids, hydrocarbon waxes, ester-based species, and chlorinated compounds . Analysis of incubation solutions by high performance liquid chromatography failed to isolate methylene dianiline (MDA) or any of its derivatives from the various polymer incubation solutions . However, a methanol extract of Corethane samples that were incubated for 28 days in cholesterol esterase did show the presence of MDA . The absence of MDA in the Pellethane methanol extracted samples may reflect the differences in surface additives found for this material versus the Corethane . FT-IR/ATR analysis of polymer surfaces exposed to cholesterol esterase/phospholipids mixture showed that there was an increase in the uptake of phospholipids over samples that were incubated in phospholipid dispersion alone . The results of this study show that some of the auxiliary chemicals found in commercial polyurethanes may hinder the specific release of hydrolytic degradation products and delay polymer degradation . However, it should be recognized that the surface layer containing these compounds is susceptible to change following the interaction between the polyurethane-based devices and elements of the host environment (i.e . lipids, enzymes, etc.) . Hence, recognition and identification of these changes will ultimately be important in assessing a commercial polymer's blood compatibility characteristics.

J Biomater Sci Polym Ed, 1999, 10(7), 699 - 713
The biodegradation of poly(urethane)s by the esterolytic activity of serine proteases and oxidative enzyme systems; Labow RS et al.; Biodegradation of poly(urethane)s (PU)s using single enzymes in vitro was assessed by measuring radiolabel release from model poly(ester-urea-urethane) (PESU) and poly(ether-urea-urethane) (PETU) materials synthesized with 14C-labelled monomers . Cholesterol esterase (CE), an enzyme found in monocyte-derived macrophages (MDM), has been reported to cause a significant level of radiolabel release from both of these PUs . Previous work has shown that CE activity could be inhibited by the serine protease/esterase inhibitor, phenylmethylsulfonyl fluoride . Since many serine proteases are present in circulating blood and can be released by cells other than MDM, this study investigated the ability of serine proteases relative to that of CE to cause the degradation of PUs . In addition, the possible role of several oxidative enzymes in the breakdown of PUs was investigated . Proteinase K, chymotrypsin and thrombin, when incubated with PESU, coated on glass slips, caused significant radiolabel release, with proteinase K giving the highest values . However, the highest radiolabel release which proteinase K could elicit was ten times less than CE . Thrombin and then chymotrypsin were progressively worse in their biodegradative activity . Only CE, and not the serine proteases, could elicit a detectable radiolabel release from PETU . Although the release of reactive oxygen species and molecular oxygen occur around an implanted biomaterial, several oxidative systems (peroxidase, xanthine oxidase, catalase), known to produce one or more of these molecular species, were unable to induce radiolabel release from these PUs . The process of biodegradation as assessed by radiolabel release appears to be a specific hydrolytic process, while the role of oxidative enzymes remains less clear.

Biodegradation, 1999 Feb, 10(1), 43 - 50
Effect of nitrogen and phosphorus addition on phenanthrene biodegradation in four soils; Johnson CR et al.; Phenanthrene mineralization rates were found to vary widely among four soils; differences in soil nutrient levels was one hypothesis to explain this variation . To test this hypothesis, phenanthrene mineralization rates were measured in these soils with, and without, added nitrogen and phosphorus . Mineralization rates either remained unchanged or were depressed by the addition of nitrogen and phosphorus . Phenanthrene degradation rates remained unchanged in the soil which had the highest indigenous levels of nitrogen and phosphorus and which showed the largest increase in phosphorus levels after nutrients were added . The soils in which degradation rates were depressed had lower initial phosphorus concentrations and showed much smaller or no measurable increase in phosphorus levels after nutrients were added to the soils . To understand the response of phenanthrene degradation rates to added nitrogen and phosphorus, it may be necessary to consider the bioavailability of added nutrients and nutrient induced changes in microbial metabolism and ecology.

Biodegradation, 1999 Feb, 10(1), 1 - 13
Biodegradation of aromatic compounds and TCE by a filamentous bacteria-dominated consortium; Bielefeldt AR et al.; The Michaelis-Menten biodegradation kinetics (k and Ks) of aromatic compounds and trichloroethene (TCE) by an aerobic enrichment culture grown on phenol and dominated by a unique filamentous bacterium were measured . The average k and Ks values for phenol, benzene (B), toluene (T), ethylbenzene (E), o-xylene (oX), p-xylene (pX), naphthalene and TCE in g per g VSS-d and mg L-1 were 5.72 and 0.34, 1.20 and 0.51, 2.09 and 0.47, 0.77 and 0.23, 0.61 and 0.16, 0.73 and 0.23, 0.17 and 0.18, and 0.16 and 0.18, respectively . Significant variability in these measured kinetics was noted between tests conducted over the 5-month period during which the fed-batch culture with a 5-day solids retention time was maintained; the coefficient of variation of the k and Ks values ranged from 11-43% and 4-50%, respectively . This variation was significantly greater than the method measurement error on a given date . Degradation of BTEoXpX mixtures could be described by a basic competitive inhibition model . Batch tests during which the culture was fed individual BTEX compounds showed the culture grew poorly on the xylenes and had poor subsequent xylene degradation rates . This work indicates the potential to simultaneously treat a mixture of volatile organic compounds using this consortium, and the ability to predict the mixture biodegradation rates on the basis of the individual compound biodegradation kinetics.

New Microbiol, 1999 Jul, 22(3), 257 - 67
Effect of novel biosurfactants on biodegradation of polychlorinated biphenyls by pure and mixed bacterial cultures; Golyshin PM et al.; A study was conducted to determine the potential positive effect of novel biosurfactants on the enhancement of Aroclor 1248 metabolization in both in vitro and in situ experiments . Among two lipopeptides tested the highest activity was found in experiments with a hydrolytically opened form of lichenysin A . Lichenysin A itself did not enhance the degradation activity of chosen microorganism-degraders and in most cases inhibited their PCB mineralization rates . Glucolipid surfactant from marine bacterium Alcanivorax borkumensis showed in several tests a strong enhancing effect on microbial metabolization of Aroclor 1248 congeners . Biosurfactants appeared to act very specifically, i.e . depending on strain and concentration used . Experiments set up with soil samples did not give a clear answer whether bioemulsifiers applied at low concentration could sufficiently increase the rates of biodegradation in situ . Only A . borkumiensis glucose lipid caused the most marked enhancement of Aroclor 1248 metabolization in soil microcosm . We suggest that taking into account the specificity of surface- and biological activities of various biosurfactants they may promote the mineralization of sorbed PCBs in polluted soils, when the optimized biosurfactant-degrader combination is used.

Chemosphere, 1999 Aug, 39(4), 627 - 39
A model for the formation and degradation of bound residues of the herbicide 14C-isoproturon in soil; Reuter S et al.; The humic monomer catechol was reacted with 14C-isoproturon and some of its metabolites, including 14C-4-isopropylaniline, in aqueous solution under a stream of oxygen . Only in the case of 14C-4-isopropylaniline, incorporation in oligomers, in fulvic acid-like polymers, and in humic acid-like polymers was observed . The main oligomer was identified by mass spectrometry as 4,5-bis-(4-isopropylphenylamino)-3,5-cyclohexadiene-1,2-dione . Oligomers and polymers containing bound 14C-4-isopropylaniline were subjected to biodegradation studies in a loamy agricultural soil during 55 days by quantifying 14CO2 evolved . In all cases, significant mineralization rates could be determined, which, however, were much smaller than those of free 14C-4-isoproturon and free 14C-4-isopropylaniline in the same soil.

Appl Microbiol Biotechnol, 1999 Jun, 51(6), 865 - 71
Biodegradation of azo dyes in cocultures of anaerobic granular sludge with aerobic aromatic amine degrading enrichment cultures; Tan NC et al.; A prerequisite for the mineralization (complete biodegradation) of many azo dyes is a combination of reductive and oxidative steps . In this study, the biodegradation of two azo dyes, 4-phenylazophenol (4-PAP) and Mordant Yellow 10 (4-sulfophenylazo-salicylic acid; MY10), was evaluated in batch experiments where anaerobic and aerobic conditions were integrated by exposing anaerobic granular sludge to oxygen . Under these conditions, the azo dyes were reduced, resulting in a temporal accumulation of aromatic amines . 4-Aminophenol (4-AP) and aniline were detected from the reduction of 4-PAP . 5-Aminosalicylic acid (5-ASA) and sulfanilic acid (SA) were detected from the reduction of MY10 . Subsequently, aniline was degraded further in the presence of oxygen by the facultative aerobic bacteria present in the anaerobic granular sludge . 5-ASA and SA were also degraded, if inocula from aerobic enrichment cultures were added to the batch experiments . Due to rapid autoxidation of 4-AP, no enrichment culture could be established for this compound . The results of this study indicate that aerobic enrichment cultures developed on aromatic amines combined with oxygen-tolerant anaerobic granular sludge can potentially be used to completely biodegrade azo dyes under integrated anaerobic/aerobic conditions.

Appl Microbiol Biotechnol, 1999 Jun, 51(6), 751 - 9
Biodegradation of EDTA; Nortemann B; The chelating agent ethylenediaminetetraacetate (EDTA) is not degraded by conventional biological and physicochemical methods for the treatment of wastewater and the purification of drinking water . Of the measurable organic compounds it is the one present at the highest concentration in many surface and drinking waters . In recent years, however, studies have demonstrated that EDTA can be degraded by specially enriched bacterial cultures and in wastewater treatment plants receiving EDTA-containing effluents . The amounts of EDTA released into the aquatic environment could thus be reduced by establishing appropriate biological wastewater treatment plants . This article describes the degradation of EDTA and its metal chelates by different bacterial cultures, catabolic steps in EDTA degradation, and biological methods for the removal of this chelating agent from wastewaters.

J Biomed Mater Res, 1999, 48(4), 522 - 7
In vivo evaluation of a novel alginate dressing; Suzuki Y et al.; Alginate dressings are currently used in the management of epidermal and dermal wounds, and provide a moist environment that leads to rapid granulation and reepithelialization . However, a cytotoxic effect on proliferation of fibroblasts and residual material with inflammation in healing wounds have been reported recently . We have developed a new alginate dressing (AGA-100), which does not have an inhibitory effect on proliferation of fibroblasts . The purpose of this study was to evaluate the new alginate dressing with respect to wound healing in full- and partial-thickness pig wounds and with respect to biodegradation following implantation into rabbit muscle . Kaltostat and Sorbsan, both well-established commercial dressings, were used as control . The closure rate of full-thickness wounds treated with AGA-100 was significantly higher on day 15 compared with that with Kaltostat and Sorbsan . Reepithelialization rate of partial-thickness wounds treated with Sorbsan was statistically significantly lower on day 3 than those with the other two dressings . As to dressing debris remained in the healing wound, a large amount of foreign debris was noted in all the full-thickness wounds treated with Kaltostat or Sorbsan, while only about one-third of wounds treated with AGA-100 showed a little dressing debris . AGA-100 implanted into the muscle of rabbits was bioresorbed completely within 3 months . Therefore, dressing residue in AGA-100-treated full-thickness wounds might be fully absorbed in a few months . In conclusion, it is shown that our newly developed AGA-100 possesses superior properties compared with typical alginate dressings .

Int J Biol Macromol, 1999 Jun-Jul, 25(1-3), 135 - 43
Extracellular degradation of medium chain length poly(beta-hydroxyalkanoates) by Comamonas sp; Quinteros R et al.; The PHA-degrading isolate, strain P37C, was enriched from residential compost for its ability to hydrolyze the medium chain length PHA, poly(beta-hydroxyoctanoate) (PHO) . It was subsequently found to grow on a wide range of PHAs, including both short chain length and medium chain length PHAs . The isolate was identified as belonging to the genus Comamonas . Strain P37C formed clear zones on poly(beta-hydroxybutyrate) (PHB), (PHO) and poly(beta-hydroxyphenylvalerate) (PHPV) overlay plates . PHA clear zone tubes were prepared using seven different kinds of PHAs, ranging from PHB with four-carbon repeating units, to poly(beta-hydroxyoctanoate-co-beta-hydroxyundecanoate) (PHOU) with 8- and 11-carbon repeating units . There was a direct correlation between PHA side chain length and rate of hydrolysis of the PHAs . A series of PHOUs containing varying percentages of unsaturated bonds were used to make a series of epoxidized PHOUs (PHOEs) with varying percentages of epoxy functions . Results of clear zone tube assays showed that these functionalized PHAs were all biodegradable by strain P37C, and there was no apparent correlation between rate of biodegradation and the proportion of functional groups in the PHAs . Biodegradability of these PHAs was verified using respirometry and enzyme assays . Cell-free supernatants containing activity toward PHAs were prepared, and strain P37C was shown to synthesize at least two distinct PHA depolymerases for the hydrolysis of SCL and MCL PHAs.

Biochemistry, 1999 Jul 13, 38(28), 8879 - 83
Aminoethylcysteine can replace the function of the essential active site lysine of Pseudomonas mevalonii 3-hydroxy-3-methylglutaryl coenzyme A reductase; Bochar DA et al.; The biodegradative 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase of Pseudomonas mevalonii catalyzes the NAD(+)-dependent conversion of (S)-HMG-CoA to (R)-mevalonate . Crystallographic analysis of abortive ternary complexes of this enzyme revealed lysine 267 located at a position in the active site, suggesting that it might serve as the general acid/base for catalysis . Site-directed mutagenesis and subsequent chemical derivatization were therefore employed to investigate this active site lysine . Replacement of lysine 267 by alanine, histidine, or arginine resulted in mutant enzymes that lacked detectable activity . Lysine 267 was next replaced by the lysine analogues aminoethylcysteine and carboxyamidomethylcysteine . Using instead of the wild-type enzyme the fully active, cysteine-free mutant enzyme C156A/C296A, lysine 267 was first replaced by cysteine . Cysteine 267 of mutant enzyme C156A/C296A/K267C was then treated with bromoethylamine or iodoacetamide to insert aminoethylcysteine (AEC) or carboxyamidomethylcysteine at position 267 . The carboxyamidomethylcysteine derivative was inactive, whereas mutant enzyme C156A/C296A/K267AEC exhibited high catalytic activity . That aminoethylcysteine, but not other basic amino acids, can replace the function of lysine 267 documents both the importance of this residue and the requirement for a precisely positioned positive charge at the active site of the enzyme.

J Pharm Pharmacol, 1999 May, 51(5), 623 - 30
Paradoxical cholinergic and purinergic vascular reactivity of rabbit thoracic aorta cold-stored in University of Wisconsin solution; Alexander B et al.; Endothelial dysfunction has been reported in donor blood vessels destined for organ transplantation following cold-storage preservation with University of Wisconsin solution (UW) . This was investigated in the present work . Segments of rabbit thoracic aorta were mounted on isometric fine-wire myographs at 37 degrees C and gassed with 95% O2/5% CO2 . Concentration-dependent vasodilatations to acetylcholine and adenosine-5'-triphosphate (ATP) were obtained in freshly-harvested rabbit aortic rings, with and without the endothelium, and after 8 days of cold-storage, at 4 degrees C, in either UW, Krebs-Bulbring buffer (KBB) or saline . The action of the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) (100 microM) was evaluated upon the concentration-response curves to determine whether nitric oxide (NO) exerted any modulatory actions . Endothelium-dependent, NO-mediated responses to acetylcholine were unaltered after eight days of storage in UW, reduced after storage in KBB and absent after removal of the vascular endothelium, saline storage or after testing in the presence of L-NAME, suggesting improved NO-mediated endothelial function with the use of UW . Structural preservation was also confirmed using scanning electron microscopy . In contrast, endothelium-dependent responses to ATP were unchanged after eight days of storage in KBB but were reduced after storage in UW and saline, suggesting purinergic (ATP) endothelial dysfunction after storage in UW . L-NAME markedly reduced vasodilatation to ATP in freshly harvested rings and after eight days of storage in KBB . This reduction was statistically significant (P < 0.05, Student's two tailed, unpaired t-test) at -log (M) ATP concentrations of 5.5, 5.0, 4.5, 4.0 and 3.5 . NO-dependent vasodilatation to ATP was not attenuated by L-NAME in UW-stored rings . Eight days' UW-storage of rabbit thoracic aortic rings appeared to have differential and paradoxical effects upon NO-dependent vasodilatation to acetylcholine and ATP . Morphological observations using electron microscopy suggested that UW preserved the vascular endothelium and this was verified by retained vascular reactivity of endothelium-dependent vasodilatations to acetylcholine . UW-storage however, significantly reduced endothelium-dependent relaxation to ATP thereby suggesting that P2Y-purinoceptors, which are located on the vascular endothelium, may be more susceptible to biodegradation than cholinergic receptors and may be responsible for endothelial dysfunction following transplantation.

Can J Microbiol, 1999 Mar, 45(3), 201 - 8
Biodegradation of cyanide compounds by a Pseudomonas species (S1); Dhillon JK et al.; A Pseudomonas sp . (S1), isolated from soil by an enrichment technique was tested for its potential to degrade different cyanide compounds . Further, biodegradation/biotransformation of binary mixtures of the cyanide compounds by the culture was also studied . The results indicated that the culture could grow on the following nitriles by using them as carbon and nitrogen sources: acetonitrile, butyronitrile, acrylonitrile, adiponitrile, benzonitrile, glutaronitrile, phenylacetonitrile, and succinonitrile . Studies on the biodegradation of these cyanide compounds in binary mixtures showed that the presence of acrylonitrile or KCN delayed the degradation of acetonitrile in a mixture, while none of the other cyanide compounds affected the degradation of one another . The transformation products of the nitriles were their corresponding acids, and similarly, KCN was also directly transformed to formic acid . Studies on the transformation of these cyanide compounds showed that the rate of transformation of nitriles to their corresponding carboxylic acids was acrylonitrile > acetonitrile > adiponitrile > benzonitrile > KCN . This culture has the unique characteristic of transforming representatives of saturated aliphatic, aliphatic olefinic, aromatic, and aralkyl nitriles, as well as alkali cyanide, to their corresponding carboxylic acids.

Rapid Commun Mass Spectrom, 1999 Jun, 13(12), 1124 - 1128
Molecular distribution of some commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; Ayorinde FO et al.; Nonylphenol ethoxylates (NPEs) belong to a group of nonionic surfactants that are collectively referred to as alkylphenol ethoxylates (APEs) . APEs find widespread use in heavy-duty commercial and household cleaning formulations, shampoos, and industrial processing, i.e . textile manufacture . Their environmental impact depends on the molecular distribution and the extent of their biodegradation in municipal sewage systems, waterways and rivers . We have established two sample preparation methods that have enabled the determination of the molecular distributions of six commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) . In both methods, alpha-cyano-4-hydroxycinnamic acid, dissolved in acetonitrile/tetrahydrofuran, was used as the matrix . In one set of experiments, the NPEs were dissolved in an acetonitrile/tetrahydrofuran solvent system prior to mixing with the matrix solution, and the resulting MALDI-TOF mass spectra produced mostly sodiated molecules {M + Na}(+) . The NPEs, all having the formula 4-(C(9)H(19))-C(6)H(4)-(OCH(2)CH(2))(n)-OH, are Surfonic (R)N-95, N-100, N-102, N-120, N-150 and N-300 . Surfonic N-95 and N-100 gave n values of 5-20; Surfonic N-102, N-120, N-150, and N-300 gave n values of 5-21, 5-22, 8-25 and 15-40, respectively . In order to develop a sample preparation method that could be used with less polar NPEs, we dissolved the NPEs (except N-300) in pentane prior to mixing with the matrix solution, and found that the MALDI spectral quality was unaffected by the solvent systems .

J Biomater Appl, 1999 Jul, 14(1), 67 - 90
Biomedical applications of polyurethanes: a review of past promises, present realities, and a vibrant future; Zdrahala RJ et al.; Polyurethanes, having extensive structure/property diversity, are one of the most bio- and blood-compatible materials known today . These materials played a major role in the development of many medical devices ranging from catheters to total artificial heart . Properties such as durability, elasticity, elastomer-like character, fatigue resistance, compliance, and acceptance or tolerance in the body during the healing, became often associated with polyurethanes . Furthermore, propensity for bulk and surface modification via hydrophilic/hydrophobic balance or by attachments of biologically active species such as anticoagulants or biorecognizable groups are possible via chemical groups typical for polyurethane structure . These modifications are designed to mediate and enhance the acceptance and healing of the device or implant . Many innovative processing technologies are used to fabricate functional devices, feeling and often behaving like natural tissue . The hydrolytically unstable polyester polyurethanes were replaced by more resistant but oxidation-sensitive polyether polyols based polyurethanes and their clones containing silicone and other modifying polymeric intermediates . Chronic in vivo instability, however, observed on prolonged implantation, became a major roadblock for many applications . Presently, utilization of more oxidation resistant polycarbonate polyols as soft segments, in combination with antioxidants such as Vitamin E, offer materials which can endure in the body for several years . The applications cover cardiovascular devices, artificial organs, tissue replacement and augmentation, performance enhancing coatings and many others . In situ polymerized, cross-linked systems could extend this biodurability even further . The future will expand this field by revisiting chemically-controlled biodegradation, in combination with a mini-version of RIM technology and minimally invasive surgical procedures, to form, in vivo, a scaffold, by delivery of reacting materials to the specific site in the body and polymerizing the mass in situ . This scaffold will provide anchor for tissue regeneration via cell attachment, proliferation, control of inflammation, and healing.

J Biomed Mater Res, 1999 Oct, 47(1), 79 - 84
Polypeptide resurfacing method improves fibroblast's adhesion to hyaluronan strands; Hu M et al.; Hyaluronic acid (hyaluronan, HyA) is a matrix component that takes part in cell adhesion and growth in normal and repaired tissues . Since it is soluble in water, HyA has been of limited use in tissue engineering of artificial matrices . Recent studies demonstrate that polypeptides have the twin advantages of reducing solubility of HyA and improving cellular attachment via cell surface adhesion molecule receptors . This paper describes a new approach of using a polypeptide resurfacing method to enhance the attachment of cells to HyA strands . HyA strands were crosslinked by glutaraldehyde and then resurfaced with poly-D-lysine, poly-L-lysine, glycine, or glutamine . After inoculation with fibroblasts in vitro, modified HyA was evaluated with histological and immunohistochemical staining methods for cell adhesion and proliferation . Modified HyA with fibroblast cells also were implanted in vivo . The results show that (1) both polylysines enhanced fibroblast adhesion to crosslinked HyA strands; (2) HyA strands were able to be crosslinked well by 3 days of treatment in glutaraldehyde, and as a biomaterial they could resist biodegradation; (3) modified HyA has good biocompatibility, both in vitro and in vivo . The results demonstrate that HyA material resurfaced by polypeptides has positive advantages for cellular adhesion . Resurfaced HyA has much potential as an improved biomaterial for clinical usage .

J Biomed Mater Res, 1999, 48(3), 265 - 76
Osteoconductivity and bone-bonding strength of high- and low-viscous bioactive bone cements; Kobayashi M et al.; A study was conducted to evaluate the osteoconductivity and bone-bonding ability of two types of bioactive bone cement, both consisting of apatite and wollastonite containing glass-ceramic powder (AW-P), fused silica glass powder (SG-P), submicron fumed silica as an inorganic filler, and bisphenol-a-glycidyl methacrylate (Bis-GMA) based resin as an organic matrix . The cements had two kinds of formulas: one (dough-type cement; designated DTC) composed of 85% (w/w) filler and 15% resin, which was developed for fixation of the acetabular component in total hip arthroplasty and could be handled manually; and one (injection-type cement; designated ITC) composed of 79% (w/w) filler and 21% resin . ITC was developed for fixation of the femoral component and, because it had a lower viscosity than DTC, could be injected . The DTC and ITC both contained 73% AW-P, 25% SG-P, and 2% fumed silica in the weight ratio of the filler component . Two other types of cement, both of which consisted of 83.3% AW-P or SG-P, 1.7% fumed silica, and 15% resin, were used as reference material (designated AWC or SGC) for a detaching test . Following the packing of bone defects in the rat tibiae with either DTC or ITC, histological examination revealed that the DTC and ITC had both directly contacted the bone and were almost completely surrounded by bone by 16 weeks after the surgery and that no marked biodegradation had occurred at 52 weeks postimplantation . Rectangular plates (2 x 10 x 15 mm) of AWC, DTC, ITC, and SGC were implanted into the metaphysis of the tibia of male rabbits and the failure load was measured by a detaching test at 10 and 25 weeks after implantation . The failure loads of AWC, DTC, ITC, and SGC were 3.65, 2.21, 2.44, and 0.04 kgf at 10 weeks and 4.87, 2 . 81, 2.82, and 0.13 kgf at 25 weeks, respectively . Observation of the bone-implant interface by scanning electron microscopy and energy dispersive X-ray microanalysis revealed that all the samples except SGC formed direct contact with the bone and that only AWC-implanted tibiae had a layer of a low calcium and phosphorus level at the bone-implant interface . Results showed that DTC and ITC have excellent osteoconductivity and bone-bonding ability under non-weight-bearing conditions .

Biotechnol Bioeng, 1999 Aug 5, 64(3), 290 - 7
Poly(ethylene glycol)-modified ligninase enhances pentachlorophenol biodegradation in water-solvent mixtures
Wang P, Woodward CA, Kaufman EN.
Polychlorinated hydrocarbons are prevalent environmental contaminants whose rates of biodegradation are limited by their minimal solubilities in aqueous solutions where the biological reactions take place . In this study, ligninase (LiP) from Phanerochaete chrysosporium was modified by poly(ethylene glycol) to enhance its activity and stability for the biodegradation of pentachlorophenol (PCP) in the presence of acetonitrile (MeCN), a water-miscible solvent . The modified enzyme retained 100% of its activity in aqueous solutions and showed enhanced tolerance against the organic solvent . The activity of the modified enzyme was found to be over twice that of the native enzyme in the presence of 10% (v/v) MeCN . The solubility of PCP was enhanced significantly by the addition of MeCN to aqueous solutions, such that it was over 10-fold more soluble in the presence of 15% (v/v) MeCN than in pure aqueous buffer solution (from 0.06 to 0.65 mM) . Capitalizing on the enhanced substrate solubility and the increased activity of the modified enzyme, the catalytic efficiency of the modified LiP in solutions containing 15% MeCN was over 11-fold higher than that of the native enzyme in buffer solutions (pH 4.2) in unoptimized reactor systems (from 44 to 480 mol PCP/mol LiP.h) . Continued research both in the use of organic solvents to increase the availability of recalcitrant contaminants and in the modification of enzymes to enhance their activity and stability in such solvents promises to dramatically affect our ability to remediate contaminated sites . Published by John Wiley & Sons.

J Biomed Mater Res, 1999 Sep 15, 46(4), 475 - 84
In vitro modulation of macrophage phenotype and inhibition of polymer degradation by dexamethasone in a human macrophage/Fe/stress system; Casas J et al.; A new in vitro accelerated biological model, the macrophage-FeCl2-stress system was used for the evaluation of dexamethasone (DEX)-polymer formulations . This model combines the effects of cells (macrophages), transition metal ions (Fe2+), and polymer stress to promote material biodegradation . The cell and material effects of DEX, either in solution or incorporated into a polyetherurethane matrix (DEX/PEU), were monitored . Cell morphology and hydroperoxide formation in the polymer during cell culturing were characterized . After a subsequent treatment with FeCl2 the development of environmental stress cracking in the polymer was evaluated . We attempted to duplicate the biodegradation of PEU in terms of environmental stress cracking (ESC) . Our results support the direct involvement of macrophages in polyetherurethane oxidation, probably by inducing hydroperoxide formation in the polymer structure . Under the influence of stress or strain, polymers with sufficient hydroperoxides degrade in the presence of Fe2+ metal ions in a manner that closely resembles the stress cracking that is observed in vivo . By contrast, polymers treated with either agents that inhibit cell activation and/or the oxidative burst, or with cells with no oxidative burst did not show signs of the biodegradative process . We demonstrated a reduction in hydroperoxide formation and no later ESC development in macrophage-cultured PEU in the presence of DEX in solution or in DEX-loaded PEU . We believe the prevention of initial polymer oxidation by reducing the cell's potential to produce oxidative stress at the tissue-biomaterial interface can directly inhibit the ESC degradation of chronically implanted polymers . The in vitro macrophage-Fe-stress system is a valuable tool for reliable assessment and cost-effective evaluation of biomaterials .

Biotechnol Bioeng, 1999 Jul 20, 64(2), 221 - 31
Biodegradation of neutralized sarin; Zhang Y et al.; This research investigated the biotransformation of IMPA, the neutralization product of the nerve agent Sarin, by a microbial consortia . As mandated by the Chemical Weapons Convention signed by 132 countries in 1993, all chemical warfare agents are to be destroyed within ten years of ratification . Technologies must be developed to satisfy this commitment . This paper presents data from a biodegradation kinetics study and background information on the biological transformation of IMPA . Microbial transformation of organophosphate nerve agents and organophosphate pesticide intermediates can be incorporated into a treatment process for the fast and efficient destruction of these similar compounds . Sarin (isopropyl methylphosphonofluoridate), also known as GB, is one of several highly neurotoxic chemical warfare agents that have been developed over the past 50 to 60 years . Four mixed cultures were acclimated to the Sarin hydrolysis product, isopropyl methylphosphonic acid (IMPA) . Two of these cultures, APG microorganisms and SX microorganisms, used IMPA as the sole phosphorus source . Extended exposure to IMPA improved the cultures' abilities to degrade IMPA to form methylphosphonic acid (MPA) and inorganic phosphate . The presence of free phosphate in the reactor suppressed the degradation of IMPA . IMPA did not inhibit either cultural consortia within the tested concentration range (0 to 1250 mg/L) . The numax was 120.9 mg/L/day for the SX microorganisms and 118.3 mg/L/day for the APG microorganisms . Initial IMPA concentrations of 85 to 90 mg/L were degraded to nondetectable levels within 75 h . These results demonstrate the potential for biodegradation to serve as a complementary treatment process for the destruction of stockpiled Sarin .

Chemosphere, 1999 Jun, 38(14), 3219 - 35
An 'inherent' biodegradability test for oil products: description and results of an international ring test . CONCAWE Biodegradation Task Force; Battersby NS et al.; Current test guidelines for assessing 'inherent' (potential) biodegradability were designed for water-soluble, organic compounds of low volatility and are unsuitable for most oil products . It was against this background, that CONCAWE (the oil companies' European organisation for environment, health and safety) formed a task force to develop a standard test protocol for assessing the 'inherent' biodegradability of oil products.

J Biomater Sci Polym Ed, 1999, 10(6), 621 - 39
Synthesis and enzymatic degradation of optically active depsipeptide copolymers; Shirahama H et al.; This paper describes the synthesis and biodegradation of copolymers of cyclic depsipeptide with epsilon-caprolactone (CL) or lactide (LA) . Optically active cyclic depsipeptides, 3,6-dimethyl-2,5-morpholinediones (DMOs), were prepared by the reaction of an amino acid (D-, L-, or DL-alanine) with a hydroxy acid derivative (DL-2-bromopropionyl bromide) . These isomers are abbreviated as D-DMO, L-DMO and DL-DMO respectively, according to the names of alanine isomers . Then, we have prepared the copolymers of DMO isomers with CL using tin(II) octylate as a catalyst . The NMR spectra and thermal properties of DMO/CL copolymers revealed that these copolymers exist randomly . The enzymatic degradation of the copolymers has been examined using Rhizopus delemar lipase, cholesterol esterase (from Pseudomonas sp.), and Proteinase K (from Tritirachium album) . Cholesterol esterase and Proteinase K show high degradability, while the lipase shows little degradation . Among the enzymes used, only Proteinase K could recognize the isomerism of DMO, resulting in the following order of degradability: copoly(L-DMO/CL) > copoly(DL-DMO/CL) > copoly(D-DMO/CL), i.e . this enzyme has the highest substrate specificity for naturally occurring L-alanine . Further, we have prepared the random copolymers of L-DMO with lactide (L-LA or DL-LA), and evaluated the enzymatic degradation of the copolymers by Proteinase K . The introduction of a small amount (up to c . 10 mol%) of L-DMO unit into LA homopolymers brought about greater degradability compared with LA homopolymers . In particular, L-DMO/L-LA copolymers with high degradability have been obtained without significant decrease in the mechanical and thermal properties of L-LA homopolymer.

Can J Microbiol, 1999 Feb, 45(2), 130 - 7
Influence of chemical surfactants on the biodegradation of crude oil by a mixed bacterial culture; Van Hamme JD et al.; The effects of surfactant physicochemical properties, such as the hydrophile-lipophile balance (HLB) and molecular structure, on the biodegradation of 2% w/v Bow River crude oil by a mixed-bacterial culture were examined . Viable counts increased 4.6-fold and total petroleum hydrocarbon (TPH) biodegradation increased 57% in the presence of Igepal CO-630, a nonylphenol ethoxylate (HLB 13, 0.625 g/L) . Only the nonylphenol ethoxylate with an HLB value of 13 substantially enhanced biodegradation . The surfactants from other chemical classes with HLB values of 13 (0.625 g/L) had no effect or were inhibitory . TPH biodegradation enhancement by Igepal CO-630 occurred at concentrations above the critical micelle concentration . When the effect of surfactant on individual oil fractions was examined, the biodegradation enhancement for the saturate and aromatic fractions was the same . In all cases, biodegradation resulted in increased resin and asphaltene concentrations . Optimal surfactant concentrations for TPH biodegradation reduced resin and asphaltene formation . Chemical surfactants have the potential to improve crude oil biodegradation in complex microbial systems, and surfactant selection should consider factors such as molecular structure, HLB, and surfactant concentration.

Biochem J, 1999 Jul 1, 341 ( Pt 1), 113 - 7
Molecular cloning of aryl-alcohol oxidase from the fungus Pleurotus eryngii, an enzyme involved in lignin degradation; Varela E et al.; Aryl-alcohol oxidase (AAO), an extracellular enzyme characteristic of fungi from the genus Pleurotus, constitutes a source for H2O2 required in lignin biodegradation . The gene aao has been cloned, sequenced and characterized for the first time in Pleurotus eryngii . Both cDNA and genomic libraries were screened with probes obtained by PCR using as primers oligonucleotides corresponding to the N-terminus and internal sequences of AAO . DNA sequences from positive clones showed a unique open reading frame of 1779 nucleotides interrupted by 12 introns . The conceptual translation of the protein agrees with the partial amino acid sequences obtained from protein sequencing . A search for proteins with related amino-acid sequences revealed that glucose oxidase from Aspergillus niger has 33% identity and 51% similarity . A comparison with other oxidoreductases showed common motifs in both N- and C-terminal regions corresponding, respectively, to the FAD-binding region and the enzyme active site . However, AAO probably has structural differences with other oxidases, as deduced from its unique ability to generate H2O2 from the oxidation of aromatic alcohols.

Biomed Chromatogr, 1999 May, 13(3), 220 - 4
Biodegradation of pentachlorophenol (PCP) by white rot fungal strains screened from local sources and its estimation by high-performance liquid chromatography; Tayal AK et al.; White rot fungal strains screened from local sources (wood trunks and from effluents of pulp and paper industry) were tested for their ability to biodegrade polymeric compounds, viz . polymeric dyes (crystal violet and brilliant green) and chlorinated phenol (pentachlorophenol) . Two of the most promising strains showing maximum degradation of polymeric dyes were selected to study the biodegradation potential and pattern of biodegradation of pentachlorophenol (PCP), a commonly used leather preservative and a potential carcinogen . PCP was quantitatively estimated and analysed by high-performance liquid chromatography (HPLC) . Conditions were optimized for the measurement of PCP on HPLC, which were: mobile phase, 60% acetonitrile and 40% water; flow rate, 1 mL/ min; column, mu Bondapack C18 RP and UV detector at 238 nm . One of the white rot fungal strains isolated from wood trunk showed a maximum 68% biodegradation of PCP in liquid-buffered medium in 16 days . The biodegradation pattern of PCP followed a pseudo-first-order kinetics . Studies on enhancement of biodegradation of polymeric dyes and PCP showed that the kinetics of biodegradation is greatly improved by the presence of manganese ions, H2O2 and glucose in the medium . This strongly suggests the involvement of peroxidase enzyme machinery of white rot fungus in the biodegradation process of PCP.

Prikl Biokhim Mikrobiol, 1999 Mar-Apr, 35(2), 165 - 72
{Protective effects of agar during immobilization of strains capable to degrade aromatic compounds}; Fedorov AIu et al.; A study of utilization of toxic monoaromatic compounds by microbial cells incorporated into agar matrix revealed positive effects of immobilization on the rate and completeness of biodegradation . This increase in the degrading activity is probably due to a strong protective effect of the polysaccharide carrier . The protective properties of agar are not due to sorptional and diffusional processes in the matrix . These properties were shown to be associated with the formation of a specific extracellular membrane around microcolonies.

Chemosphere, 1999 Jun, 38(15), 3627 - 36
Enhancement of PAH biodegradation in soil by physicochemical pretreatment; Bonten LT et al.; The effects were studied of short-term heating of contaminated soil and its soaking in an organic solvent on the subsequent biodegradation of PAHs . In a clayey dredged sludge with a high organic-matter content (12%), heating at 120 degrees C for one hour increased the degree of degradation after 21 days of an aged PAH contamination from 9.5 +/- 0.7% to 27 +/- 5% . Lower temperatures resulted in smaller increases . The observed increase in biodegradation is caused by either transfer of PAHs from sorption sites with low desorption rates to those with high ones or transformation of slow-sorption sites into fast-sorption ones . Soaking of the above sludge in a 4:1 (v/v) acetone-water mixture increased the degree of degradation from 9.5 +/- 0.7% to 20.4 +/- 1.4%, probably as a result of dissolution of the PAHs in the pore liquid during soaking . Thermal pretreatment of a contaminated sandy soil with a low organic-matter content showed no significant effect on the degradation of aged PAHs . Soaking of the sandy soil increased the degradation of only PAHs of high molecular weight, namely from 24 +/- 5% to 48 +/- 7%.

Chemosphere, 1999 Jun, 38(15), 3463 - 72
Biodegradation of diesel oil by cold-adapted microorganisms in presence of sodium dodecyl sulfate; Margesin R et al.; The effect of different concentrations of the anionic surfactant sodium dodecyl sulfate (SDS) on biodegradation of diesel oil was assessed during 32 days at 10 degrees C, under simulated environmental conditions, in liquid culture and in an alpine soil . Low SDS concentrations (50-100 mg l-1) significantly enhanced oil biodegradation by a psychrotrophic inoculum in liquid culture, whereas higher SDS concentrations (500-1000 mg l-1) inhibited hydrocarbon biodegradation . Oil biodegradation by the indigenous microorganisms in soil was inhibited at all SDS concentrations tested . The surfactant itself was rapidly biodegraded both in liquid culture and in soil.

J Biotechnol, 1999 Apr 15, 69(2-3), 151 - 62
Glucose 1- and 2-oxidases from fungal strains: isolation and production of monoclonal antibodies; Karmali A et al.; Monoclonal antibodies (Mabs) against purified glucose 2-oxidase (EC 1.1.3.10) from Coriolus versicolor were raised by hybridoma technology using Sp2/0 myeloma cells as a fusion partner . Hybrid growth was observed in 42% of culture wells and 30% of these (i.e . 30 culture wells) contained anti-glucose 2-oxidase activity . Three positive wells containing hybrid cell lines were selected and cloned twice by the limiting dilution method and two hybridoma clones (E1A5 and E1A6) secreting Mabs were selected at random for purification and characterisation purposes . Both cell lines secreted Mabs of IgM class which were purified by gel filtration chromatography on a Sephacryl S-200 column with a final recovery of 80% and a purification factor of 16 . The purified preparations were apparently homogeneous on native PAGE running with a M(r) of 950 kDa . Mabs were highly specific for glucose 2-oxidase as determined by Western blotting . These Mabs also crossreacted with glucose 1- and 2-oxidases from other fungal sources (Phanerochaeta chrysosporium, Penicillium amagasakiense and Aspergillus niger) as determined by Western blotting and by ELISA . Both glucose 1- and 2-oxidases from C . versicolor, P . chrysosporium, P . amagasakiense and A . niger were purified by hydrophobic interaction chromatography on Sepharose 4B-triazine dye with a recovery of enzyme activity in the range 85-92% . Purified preparations of glucose oxidases from fungal strains were apparently homogeneous on native PAGE . Glucose 2-oxidases were more hydrophobic than glucose 1-oxidases as determined by their chomatographic behaviour on Sepharose 4B-Cibacron Red G-E which could be used to study their roles in lignin biodegradation.

Tissue Eng, 1999 Apr, 5(2), 127 - 38
Biodegradation of hydrogel carrier incorporating fibroblast growth factor; Tabata Y et al.; In vivo release of basic fibroblast growth factor (bFGF) from a biodegradable gelatin hydrogel carrier was compared with the in vivo degradation of hydrogel . When gelatin hydrogels incorporating 125I-labeled bFGF were implanted into the back subcutis of mice, the bFGF radioactivity remaining decreased with time and the retention period was prolonged with a decrease in the water content of the hydrogels . The lower the water content of 125I-labeled gelatin hydrogels, the faster both the weight of the hydrogels and the gelatin radioactivity remaining decreased with time . The decrement profile of bFGF remaining in hydrogels was correlated with that of hydrogel weight and gelatin radioactivity, irrespective of the water content . Subcutaneous implantation of bFGF-incorporating gelatin hydrogels into the mice induced significant neovascularization . The retention period of neovascularization became longer as the water content of the hydrogels decreased . To study the decrease of activity of bFGF when implanted, bFGF-incorporating hydrogels were placed in diffusion chamber and implanted in the mouse subcutis for certain periods of time . When hydrogels explanted from the mice were again implanted, significant neovascularization was still observed, indicating that most of the biological activity of bFGF was retained in the hydrogels . It was concluded that, in our hydrogel system, biologically active bFGF was released as a result of in vivo degradation of the hydrogel . The release profile was controllable by changing the water content of hydrogels.

Biotechnol Prog, 1999 May, 15(3), 517 - 21
Organophosphorus hydrolase-based assay for organophosphate pesticides
Rogers KR, Wang Y, Mulchandani A, Mulchandani P, Chen W.
We report a rapid and versatile organophosphorus hydrolase (OPH)-based method for measurement of organophosphates . This assay is based on a substrate-dependent change in pH at the local vicinity of the enzyme . The pH change is monitored using fluorescein isothiocyanate (FITC), which is covalently immobilized to the enzyme . This method employs the use of poly(methyl methacrylate) beads to which the FITC-labeled enzyme is adsorbed . Analytes were then measured using a microbead fluorescence analyzer . The dynamic concentration range for the assay extends from 25 to 400 &mgr;M for paraoxon with a detection limit of 8 &mgr;M . Organophosphorus insecticides measured using this technique included ethylparathion, methylparathion, dursban, fensulfothion, crotoxyphos, diazinon, mevinphos, dichlorvos, and coumaphos . This technique was used to measure coumaphos in biodegradation samples of cattle dip wastes and showed a high correlation (r2 = 0.998) to an HPLC method.

Appl Environ Microbiol, 1999 Jun, 65(6), 2376 - 81
Earthworm egg capsules as vectors for the environmental introduction of biodegradative bacteria; Daane LL et al.; Earthworm egg capsules (cocoons) may acquire bacteria from the environment in which they are produced . We found that Ralstonia eutropha (pJP4) can be recovered from Eisenia fetida cocoons formed in soil inoculated with this bacterium . Plasmid pJP4 contains the genes necessary for 2,4-dichlorophenoxyacetic acid (2,4-D) and 2, 4-dichlorophenol (2,4-DCP) degradation . In this study we determined that the presence of R . eutropha (pJP4) within the developing earthworm cocoon can influence the degradation and toxicity of 2,4-D and 2,4-DCP, respectively . The addition of cocoons containing R . eutropha (pJP4) at either low or high densities (10(2) or 10(5) CFU per cocoon, respectively) initiated degradation of 2,4-D in nonsterile soil microcosms . Loss of 2,4-D was observed within the first week of incubation, and respiking the soil with 2,4-D showed depletion within 24 h . Microbial analysis of the soil revealed the presence of approximately 10(4) CFU R . eutropha (pJP4) g-1 of soil . The toxicity of 2,4-DCP to developing earthworms was tested by using cocoons with or without R . eutropha (pJP4) . Results showed that cocoons containing R . eutropha (pJP4) were able to tolerate higher levels of 2,4-DCP . Our results indicate that the biodegradation of 2, 4-DCP by R . eutropha (pJP4) within the cocoons may be the mechanism contributing to toxicity reduction . These results suggest that the microbiota may influence the survival of developing earthworms exposed to toxic chemicals . In addition, cocoons can be used as inoculants for the introduction into the environment of beneficial bacteria, such as strains with biodegradative capabilities.

J Craniomaxillofac Surg, 1999 Apr, 27(2), 124 - 33
Fixation of mandibular body osteotomies using biodegradable amorphous self-reinforced (70L:30DL) polylactide or metal lag screws: an experimental study in sheep; Kallela I et al.; Mandibular body osteotomies were fixed in nine sheep using new totally amorphous (70L:30DL), self-reinforced, polylactide (SR-PLA) lag screws and in nine sheep using standard stainless steel lag screws . No intermaxillary fixation was used . During follow-up, radiological, histological and microradiological studies were undertaken at 3, 6, 12 and 24 weeks . In both groups, all osteotomies consolidated at similar rates and no adverse reaction to the screws was seen . However, displacements of the fixed osteotomy fragments were common in both groups during the first 3 weeks . The biocompatibility of SR-PLA during the follow-up period was found to be good . Only initial signs of biodegradation were seen . The results of this study indicate that (70L:30DL) SR-PLA has potential for use as a fixation screw material in oral and maxillofacial surgery, and that further studies using this material are justified.

Appl Microbiol Biotechnol, 1999 Apr, 51(4), 532 - 5
Aerobic degradation of a hydrocarbon mixture in natural uncontaminated potting soil by indigenous microorganisms at 20 degrees C and 6 degrees C; Eriksson M et al.; A hydrocarbon mixture containing p-xylene, naphthalene, Br-naphthalene and straight aliphatic hydrocarbons (C14 to C17) was aerobically degraded without lag phase by a natural uncontaminated potting soil at 20 degrees C and 6 degrees C . Starting concentrations were approximately 46 ppm for the aromatic and 13 ppm for the aliphatic compounds . All aliphatic hydrocarbons were degraded within 5 days at 20 degrees C, to levels below detection (ppb levels) but only down to 10% of initial concentration at 6 degrees C . Naphthalene was degraded within 12 days at 20 degrees C and unaffected at 6 degrees C . At 20 degrees C p-xylene was degraded within 20 days, but no degradation occurred at 6 degrees C . Br-naphthalene was only removed down to 30% of initial concentration at 20 degrees C, with no significant effect at 6 degrees C . The biodegradation was monitored with head space solid-phase microextraction and gas chromatography-mass spectrometry.

Biodegradation, 1998, 9(6), 433 - 42
Thiomorpholine and morpholine oxidation by a cytochrome P450 in Mycobacterium aurum MO1 . Evidence of the intermediates by in situ 1H NMR; Combourieu B et al.; Spectrophotometric assays of Mycobacterium aurum MO1 cells extracts gave evidence of a soluble cytochrome P450, involved in the degradative pathway of morpholine, a waste product from the chemical industry . In order to get further information, the kinetics of the biodegradation of the sulfur analogue thiomorpholine was monitored by using in situ nuclear magnetic resonance (NMR) . This technique allowed the identification of two intermediates: the sulfoxide of thiomorpholine resulting from S-oxidation and thiodiglycolic acid owing to ring cleavage . The S-oxidation (S-->SO) represents one of the well-known reactions catalyzed by cytochromes P450 . The inhibitory effect of metyrapone, a cytochrome P450 inhibitor, on the thiomorpholine and morpholine degradative abilities of M . aurum MO1 confirmed the involvement of a cytochrome P450 . These results and the decrease of the rate of formation of the first intermediate during the morpholine degradation, 2-(2-aminoethoxy) acetate, proved the key role of the cytochrome P450 in the early events of the biodegradation, i.e., in the C-N bond cleavage.

Biodegradation, 1998, 9(6), 423 - 31
Application of 13C NMR to investigate the transformations and biodegradation of organic materials by wood- and soil-feeding termites, and a coprophagous litter-dwelling dipteran larva; Hopkins DW et al.; Solid-state 13C nuclear magnetic resonance spectroscopy has been used to characterize the C in samples of the food (wood), gut contents and faeces from the wood-feeding termite, Microcerotermes parvus; soil in the guts and mound material from the soil-feeding termite, Thoracotermes macrothorax; and the food and faeces from the litter-feeding, coprophagous larvae of the dipteran fly, Bibio marci . Spectra from the wood-feeding termite indicated preferential loss of polysaccharide and accumulation of lignin with some modification to the O-aromatic-C and methoxyl-C (O-methyl-C) components during passage through the gut . Spectra for the soil-feeding termite indicated little change in the distribution of 13C between resonances following passage through the gut, except for some evidence of preferential polysaccharide loss . Interpretation of the spectra from these organisms was restricted by the relatively low C content of the soils and mound material, and by the large contribution to the NMR spectra from the gut tissue rather than the gut contents . Spectra for the litter-feeding dipteran larvae indicated preferential feeding on the polysaccharide-rich component of the litter and then overall loss of polysaccharide-C and accumulation of both aromatic-C and methoxyl-C in the gut . These changes were greater for the second passage than for the first passage through the gut, suggesting that principally mechanical and physical changes occurred initially and that chemical digestion was prevalent during the second passage.

Biochem Biophys Res Commun, 1999 May 27, 259(1), 212 - 9
Coupling of manganese peroxidase-mediated lipid peroxidation with destruction of nonphenolic lignin model compounds and 14C-labeled lignins; Kapich A et al.; Linoleic acid, the predominant unsaturated fatty acid (UFA) in the lipids of wood-rotting fungi, was oxidized by manganese peroxidase (MnP) from the white-rot fungus Phlebia radiata through a peroxidation mechanism . The peroxidation was markedly stimulated by hydrogen peroxide . UFAs that are substrates for lipid peroxidation and surfactants that emulsify water-insoluble components were essential for the MnP-catalyzed destruction of a nonphenolic beta-O-4-linked lignin model compound (LMC) . Moreover, both components stimulated the MnP-catalyzed mineralization of 14C-labeled synthetic lignin and 14C-labeled wheat straw . A high level of destruction was obtained in reaction systems with Tween 80 acting both as surfactant and source of UFAs . The presence of the linoleic acid in reaction systems with MnP and Tween 80 additionally enhanced rate and level of LMC destruction and lignin mineralization . The results indicate that lipid peroxidation may play an important role in lignin biodegradation by wood-rotting basidiomycetes and support the hypothesis of coupling between the processes .

Ecotoxicol Environ Saf, 1999 May, 43(1), 47 - 56
Biodegradation of s-triazine compounds by a stable mixed bacterial community; Kontchou CY et al.; The potential for biodegradation of s-triazine pesticides was investigated in laboratory batch and sequence batch experiments using a stable mixed bacterial community enriched on atrazine . The experiments were performed aerobically in a mineral salt solution complemented with a mixture of s-triazines as sole carbon and energy sources . Comparisons were made between the efficiency of the inoculum for atrazine degradation in mineral salt solution and in wastewater . In batch cultivation, atrazine, simazine, hydroxyatrazine, and terbutylazine were degraded to concentrations below 0.1 mg/liter after 6 days; evidence of the mineralization was the detection of 14CO2 from {U-ring-14C} atrazine and the production of nitrate and chloride ions . The low degradation rate observed for cyanuric acid and desethylatrazine suggests that degradation proceeded via N-dealkylation and dechlorination . Nevertheless, degradation of ametryne and cyromazine presume the involvement of other degradation pathways . Evidence was given that presence of other additional carbon sources is not an obstacle to atrazine biodegradation, since better results were obtained using wastewater .

Rev Argent Microbiol, 1999 Jan-Mar, 31(1), 42 - 8
{Degradation of naphthalene-2-sulfonate by strains of Micromonospora}; Vidal CM et al.; It was possible to isolate several strains of Micromonospora sp . from waters of Rio Reconquista . They all were filamentous bacteria with lateral spores, highly resistant to Cr(III) and another heavy metal cations . All these strains were able to grow on naphthalene-2-sulphonate as sole carbon source in a mineral medium . The biodegradation of the xenobiotic proceeds via the formation of salicylate and gentisate . These compounds have been isolated and mass spectrometry identified.

Chemosphere, 1999 Jun, 38(13), 3109 - 17
Microbial degradation of 4-chlorophenol by microorganisms entrapped in carrageenan-chitosan gels; Wang J et al.; A new cell immobilization method based on the replacement of KCl by KCl + chitosan as gelling agent was developed . The results showed that through addition of chitosan into gelling agent, the mechanical strength and thermal stability of the carrageenan gel were greatly improved . The new immobilization method was used to entrap a chlorophenol-degrading microorganism . The immobilized microbial cells were applied for chlorophenol biodegradation . The experiments demonstrated that immobilized cells exhibit a higher bioactivity in the degradation of chlorophenol than free cells.

FEMS Microbiol Lett, 1999 Apr 15, 173(2), 445 - 52
Fate of phenanthrene, pyrene and benzo{a}pyrene during biodegradation of crude oil added to two soils; Smith MJ et al.; The release of 14CO2 from 9-{14C}phenanthrene, 4,5,9,10-{14C}pyrene and 7-{14C}benzo{a}pyrene, added to Brent/Fortes crude oil and mixed into a pristine sand soil (0.40% organic C) and a pristine organic soil (22.9% organic C), was determined . After 244 days at 25 degrees C, 11.1 +/- 3.5% (sand) and 17.1 +/- 0.30% (organic) phenanthrene-14C and 9.77 +/- 2.8% (sand) and 5.86 +/- 1.4% (organic) benzo{a}pyrene-14C was released . After 210 days, 3.65 +/- 0.5% (sand) and 4.43 +/- 0.33% (organic) pyrene-14C was released . Inoculation of these two soils with DC1 and PD2 (bacteria capable of accelerating the phenanthrene and pyrene mineralisation in soil in the absence of crude oil) either at day 0 or after release as 14CO2 by indigenous degraders had ceased, failed to increase or initiate further mineralisation . Thus, aged PAH residues were non-bioavailable to these metabolically competent degrading microorganisms . At the end of the first period of incubation (210 days or 244 days), the total aromatic hydrocarbons recovered using Soxhlet extraction was 0.18% (sand) and 42.8% (organic) compared with approximately 100% from bio-inhibited soils . This confirmed that the indigenous microbiological activity not only caused a limited amount of PAH mineralisation but also reduced the extractability of residues, possibly due to the generation of metabolites which were chemisorbed and bound (and non extractable) in 'aged' soils.

Chirality, 1999, 11(4), 330 - 7
Plant and soil enantioselective biodegradation of racemic phenoxyalkanoic herbicides; Schneiderheinze JM et al.; The biodegradation of the chiral phenoxyalkanoic herbicides 2-(2,4-dichlorophenoxy)propionic aid (2,4-DP) and 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP) was investigated using enantioselective HPLC and chiroptical detection . Racemic mixtures of 2,4-DP and MCPP were applied to three species of turf grass, four species of broadleaf weeds, and soil . Preferential degradation of the S-(-) enantiomer of each herbicide was observed in most species of broadleaf weeds and soil, while the degradation in all species of grass occurred without enantioselectivity . The biodegradation in all systems appeared to follow pseudo first-order kinetics with the fastest degradation occurring in broadleaf weeds, followed by the grasses . The slowest degradation was observed in soil . The results of this work illustrate the need to characterize both enantiomers of chiral agrochemicals in order to have an accurate understanding of their distribution and fate in the environment.

Appl Environ Microbiol, 1999 May, 65(5), 2143 - 50
Molecular analysis of microbial community structures in pristine and contaminated aquifers: field and laboratory microcosm experiments; Shi Y et al.; This study used phylogenetic probes in hybridization analysis to (i) determine in situ microbial community structures in regions of a shallow sand aquifer that were oxygen depleted and fuel contaminated (FC) or aerobic and noncontaminated (NC) and (ii) examine alterations in microbial community structures resulting from exposure to toluene and/or electron acceptor supplementation (nitrate) . The latter objective was addressed by using the NC and FC aquifer materials for anaerobic microcosm studies in which phylogenetic probe analysis was complemented by microbial activity assays . Domain probe analysis of the aquifer samples showed that the communities were predominantly Bacteria; Eucarya and Archaea were not detectable . At the phylum and subclass levels, the FC and NC aquifer material had similar relative abundance distributions of 43 to 65% beta- and gamma-Proteobacteria (B+G), 31 to 35% alpha-Proteobacteria (ALF), 15 to 18% sulfate-reducing bacteria, and 5 to 10% high G+C gram positive bacteria . Compared to that of the NC region, the community structure of the FC material differed mainly in an increased abundance of B+G relative to that of ALF . The microcosm communities were like those of the field samples in that they were predominantly Bacteria (83 to 101%) and lacked detectable Archaea but differed in that a small fraction (2 to 8%) of Eucarya was detected regardless of the treatment applied . The latter result was hypothesized to reflect enrichment of anaerobic protozoa . Addition of nitrate and/or toluene stimulated microbial activity in the microcosms, but only supplementation of toluene alone significantly altered community structures . For the NC material, the dominant subclass shifted from B+G to ALF, while in the FC microcosms 55 to 65% of the Bacteria community was no longer identifiable by the phylum or subclass probes used . The latter result suggested that toluene exposure fostered the proliferation of phylotype(s) that were otherwise minor constituents of the FC aquifer community . These studies demonstrated that alterations in aquifer microbial communities resulting from specific anthropogenic perturbances can be inferred from microcosm studies integrating chemical and phylogenetic probe analysis and in the case of hydrocarbon contamination may facilitate the identification of organisms important for in situ biodegradation processes . Further work integrating and coordinating microcosm and field experiments is needed to explore how differences in scale, substrate complexity, and other hydrogeological conditions may affect patterns observed in these systems.

Appl Environ Microbiol, 1999 May, 65(5), 1834 - 42
Formation of bound residues during microbial degradation of {14C}anthracene in soil; Kastner M et al.; Carbon partitioning and residue formation during microbial degradation of polycyclic aromatic hydrocarbons (PAH) in soil and soil-compost mixtures were examined by using {14C}anthracenes labeled at different positions . In native soil 43.8% of {9-14C}anthracene was mineralized by the autochthonous microflora and 45.4% was transformed into bound residues within 176 days . Addition of compost increased the metabolism (67.2% of the anthracene was mineralized) and decreased the residue formation (20 . 7% of the anthracene was transformed) . Thus, the higher organic carbon content after compost was added did not increase the level of residue formation . {14C}anthracene labeled at position 1,2,3,4,4a,5a was metabolized more rapidly and resulted in formation of higher levels of residues (28.5%) by the soil-compost mixture than {14C}anthracene radiolabeled at position C-9 (20.7%) . Two phases of residue formation were observed in the experiments . In the first phase the original compound was sequestered in the soil, as indicated by its limited extractability . In the second phase metabolites were incorporated into humic substances after microbial degradation of the PAH (biogenic residue formation) . PAH metabolites undergo oxidative coupling to phenolic compounds to form nonhydrolyzable humic substance-like macromolecules . We found indications that monomeric educts are coupled by C-C- or either bonds . Hydrolyzable ester bonds or sorption of the parent compounds plays a minor role in residue formation . Moreover, experiments performed with 14CO2 revealed that residues may arise from CO2 in the soil in amounts typical for anthracene biodegradation . The extent of residue formation depends on the metabolic capacity of the soil microflora and the characteristics of the soil . The position of the 14C label is another important factor which controls mineralization and residue formation from metabolized compounds.

Biomaterials, 1999 Mar, 20(6), 561 - 71
Biodegradation of polysiloxanes in lymph nodes of rats measured with 29Si NMR; Pfleiderer B et al.; Linear and cyclic polysiloxanes and extracts (free polymer) from a silicone gel-filled implant are used to investigate the reactivity of silicones in vivo . Aqueous emulsions of polysiloxanes and controls (without polysiloxanes) are injected once (day 0, approximately 10% w/v) or six times (starting at day 0, every 14 days, approximately 3% w/v) in the right thigh of rats and the popliteal and lumbar lymph nodes are harvested (3 rats per time point and compound investigated) at 2, 16, 30, 44, 58 and 72 days after the injection . 29Si NMR spectroscopy is used to detect and evaluate the presence of polysiloxanes and their metabolites in the lymph nodes . In addition to the resonance associated with the polysiloxane injected (approximately -20 ppm), the NMR spectra of lymph nodes show new resonances that are attributed to partially hydrolyzed polysiloxanes (-5 to -15 ppm) and silica (-90 to - 120 ppm) . These resonances are not present in polysiloxanes emulsions before injection or in the lymph nodes of controls . Our results demonstrate that all polysiloxanes and extracts from silicone gel-filled implants are biotransformed in the lymph nodes, but high molecular weight polymer degrades at a slower rate than oligomers.

Chemosphere, 1999 May, 38(11), 2501 - 7
In-vitro study of interaction between photooxidation and biodegradation of 2-methylphenanthrene by Sphingomonas SP . 2MPII; Ni'matuzahroh et al.; This work reports a study of interactions between reactions of photooxidation and reactions of bacterial degradation of an alkylated polyaromatic hydrocarbon (2-methylphenanthrene) . Bacterial growth was carried out using artificial sunlight as light source . Among the various products detected, the major product was identified as the 2-methylphenanthrene aldehyde . Sunlight allows accelerated elimination of the substrate . This enhancement of the biodegradation rate of 2 methylphenanthrene is due to the use of assimilable photoproducts by the bacterium.

Chemosphere, 1999 May, 38(11), 2455 - 60
Biodegradation of azo dyes by the yeast Candida zeylanoides in batch aerated cultures; Martins MA et al.; A number of simple azo dyes was degraded in liquid aerated batch cultures by a strain of the yeast Candida zeylanoides . The standard decolorization medium contained glucose as a carbon and energy source, and its pH was either controlled to 5.0-5.2, or allowed to decrease to 3.2-2.8, in the course of microorganism growth . The extent of colour removal in the culture medium was assessed through the decrease in dye absorbance of the supernatants . The extent of colour removal ranged from 44 to 90%, after 7 days, for 5 out of 6 dyes studied in shaked cultures, without pH control, and from 46 to 67%, after 22 hours, for 6 out of 8 dyes in batch experiments, at controlled pH.

Lett Appl Microbiol, 1999 Mar, 28(3), 238 - 41
Biodegradation of lindane (gamma-hexachlorocyclohexane) by the white-rot fungus Trametes hirsutus; Singh BK et al.; The ability of the white-rot fungus Trametes hirsutus to degrade an insecticide, lindane, in liquid culture was investigated and compared with that of Phanerochaete chrysosporium . Trametes hirsutus degraded lindane faster than P . chrysosporium but the mechanism of degradation appears to be the same in both . Two metabolites identified in both fungi were tetrachlorocyclohexane and tetrachlorocyclohexanol . The presence of lindane alone inside the mycelium ruled out the involvement of any intracellular enzyme(s) during the initial step of lindane degradation . Lindane at a concentration of 0.27 mumol l-1 exhibited no adverse effect on fungal growth.

Biodegradation, 1998, 9(5), 369 - 79
Effect of calcium on the surfactant tolerance of a fluoranthene degrading bacterium; Willumsen PA et al.; Surfactants are known to increase the apparent aqueous solubility of polycyclic aromatic hydrocarbons (PAHs) and may thus be used to enhance the bioavailability and thereby to stimulate the biodegradation of these hydrophobic compounds . However, surfactants may in some cases reduce or inhibit biodegradation because of toxicity to the bacteria . In this study, toxicity of surfactants on Sphingomonas paucimobilis strain EPA505 and the effect on fluoranthene mineralization were investigated using Triton X-100 as model surfactant . The data showed that amendment with 0.48 mM (0.3 g l-1) of Triton X-100 completely inhibited fluoranthene and glucose mineralization and reduced cell culturability by 100% in 24 h . Electron micrographs indicate that Triton X-100 adversely affects the functioning of the cytoplasmic membrane . However, in the presence of 4.13 mM Ca(2+)-ions, Triton X-100 more than doubled the maximum fluoranthene mineralization rate and cell culturability was reduced by only 10% . In liquid cultures divalent ions, Ca2+ in particular and Mg2+ to a lesser extent, were thus shown to be essential for the surfactant-enhanced biodegradation of fluoranthene . Most likely the Ca(2+)-ions stabilized the cell membrane, making the cell less sensitive to Triton X-100 . This is the first report on a specific factor which is important for successful surfactant-enhanced biodegradation of PAHs.

Biodegradation, 1998, 9(5), 343 - 57
Microbial degradation of tannins--a current perspective; Bhat TK et al.; Tannins are water-soluble polyphenolic compounds having wide prevalence in plants . Hydrolysable and condensed tannins are the two major classes of tannins . These compounds have a range of effects on various organisms--from toxic effects on animals to growth inhibition of microorganisms . Some microbes are, however, resistant to tannins, and have developed various mechanisms and pathways for tannin degradation in their natural milieu . The microbial degradation of condensed tannins is, however, less than hydrolysable tannins in both aerobic and anaerobic environments . A number of microbes have also been isolated from the gastrointestinal tract of animals, which have the ability to break tannin-protein complexes and degrade tannins, especially hydrolysable tannins . Tannase, a key enzyme in the degradation of hydrolysable tannins, is present in a diverse group of microorganisms, including rumen bacteria . This enzyme is being increasingly used in a number of processes . Presently, there is a need for increased understanding of the biodegradation of condensed tannins, particularly in ruminants.

Syst Appl Microbiol, 1999 Feb, 22(1), 113 - 8
Importance of Xanthobacter autotrophicus in toluene biodegradation within a contaminated stream; Tay ST et al.; Toluene-degrading strains T101 and T102 were isolated from rock surface biomass in a toluene-contaminated freshwater stream . These organisms were present at a density of 5.5 x 10(6) cells/g of rock surface biomass . Both are aerobic, rod-shaped, Gram-negative, non-motile, catalase-positive, oxidase-positive, with yellow pigments, and can grow on benzene . Phylogenetic analyses show that strains T101 and T102 have 16S rDNA sequences identical to Xanthobacter autotrophicus . Fatty acid analyses indicate that they are different strains of the same species Xanthobacter autotrophicus, and that they have high levels of cis-11-octadecenoic acid and cis-9-hexadecenoic acid; 3-hydroxyhexadecanoic acid is the major hydroxy fatty acid present . Strains T101 and T102 had maximal velocities (Vmax) for toluene biodegradation of 3.8 +/- 0.5 and 28.3 +/- 2.2 mumoles toluene/mgprotein-hr, and half-saturation constants (Ks) of 0.8 +/- 0.5 and 11.5 +/- 2.4 microM, respectively . Strain T102 has a higher capacity than strain T101 to degrade toluene, and kinetic calculations suggest that strain T102 may be a major contributor to toluene biodegradation in the stream.

J Craniomaxillofac Surg, 1999 Feb, 27(1), 42 - 50
SR-PLLA and SR-PGA miniscrews: biodegradation and tissue reactions in the calvarium and dura mater; Peltoniemi HH et al.; The biocompatibility and degradation of self-reinforced poly-L-lactide (SR-PLLA) and polyglycolide (SR-PGA) miniscrews, vs titanium miniscrews, was studied in frontal bone osteotomies in 20 lambs, where they were used for plate fixation . At follow-up at 4, 6, 12, 26, 52 and 104 weeks, no clinical foreign body reaction, infection or other complications had occurred . Histologically, PGA material was hydrolyzed and fragmented at 4-6 weeks and was resorbed by 12 weeks, whereas the SR-PLLA miniscrews retained their integrity and holding power for 26 weeks and were mostly resorbed at 2 years . According to histological and histomorphometric analyses and plain film radiography, the degradation of PGA miniscrews was accompanied by a typical non-specific foreign-body reaction and initial transient osteolysis with decreased osteoid formation around the screw channel, but compensatory intense osteoid formation and bone remodelling followed after resorption of the polymer . The foreign body reactions to PLLA and titanium were considerably milder . All miniscrews were commendably strong and could be satisfactorily tightened against the plate . SR-PLLA miniscrews offer fixation stability for half a year, whereas rapidly degrading SR-PGA miniscrews may be used when short-term fixation is needed.

J Appl Biomater, 1990 Fall, 1(3), 241 - 8
Preliminary development of a hydroxyapatite-backed strain gauge; Szivek JA et al.; Long-term in vivo strain sensing would provide information about deformation changes adjacent to implants during bone remodeling . Biodegradation of the cyanoacrylate adhesive commonly used to attach strain gauges to bone has generally limited in vivo strain sensing to time periods less than one month . Hydroxyapatite (HA) which has been used to attach implants to bone in vivo, was attached to strain gauges using a solvent-thinned polysulfone solution . Three HA-polysulfone surface morphologies were tested in a preliminary bench-top test . The single layer pressed surface morphology, which responded most accurately during bench-top testing, was modified slightly and applied to two gauges which were implanted on the femur of a greyhound . Strain measurements from the HA-backed gauges in place for four months in vivo were compared to strains measured from the contralateral femur . Comparison of the results indicated these gauges were well-bonded and that they were sensing strain accurately . After embedding in PMMA, the femur having the HA-backed gauge and the control femur were sectioned at the level of one of the HA-backed gauges . Microradiographs of these sections indicated no adverse tissue response to the HA-backed gauge on the endosteal or periosteal surface.

Appl Environ Microbiol, 1999 Apr, 65(4), 1806 - 10
Genetic analysis of biodegradation of tetralin by a Sphingomonas strain; Hernaez MJ et al.; A strain designated TFA which very efficiently utilizes tetralin has been isolated from the Rhine river . The strain has been identified as Sphingomonas macrogoltabidus, based on 16S rDNA sequence similarity . Genetic analysis of tetralin biodegradation has been performed by insertion mutagenesis and by physical analysis and analysis of complementation between the mutants . The genes involved in tetralin utilization are clustered in a region of 9 kb, comprising at least five genes grouped in two divergently transcribed operons.

Appl Environ Microbiol, 1999 Apr, 65(4), 1405 - 12
Initial reactions in the biodegradation of 1-chloro-4-nitrobenzene by a newly isolated bacterium, strain LW1; Katsivela E et al.; Bacterial strain LW1, which belongs to the family Comamonadaceae, utilizes 1-chloro-4-nitrobenzene (1C4NB) as a sole source of carbon, nitrogen, and energy . Suspensions of 1C4NB-grown cells removed 1C4NB from culture fluids, and there was a concomitant release of ammonia and chloride . Under anaerobic conditions LW1 transformed 1C4NB into a product which was identified as 2-amino-5-chlorophenol by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry . This transformation indicated that there was partial reduction of the nitro group to the hydroxylamino substituent, followed by Bamberger rearrangement . In the presence of oxygen but in the absence of NAD, fast transformation of 2-amino-5-chlorophenol into a transiently stable yellow product was observed with resting cells and cell extracts . This compound exhibited an absorption maximum at 395 nm and was further converted to a dead-end product with maxima at 226 and 272 nm . The compound formed was subsequently identified by 1H and 13C NMR spectroscopy and mass spectrometry as 5-chloropicolinic acid . In contrast, when NAD was added in the presence of oxygen, only minor amounts of 5-chloropicolinic acid were formed, and a new product, which exhibited an absorption maximum at 306 nm, accumulated.

Chemosphere, 1999 Apr, 38(9), 2029 - 39
Measuring the biodegradability of nonylphenol ether carboxylates, octylphenol ether carboxylates, and nonylphenol; Staples CA et al.; We examined the biodegradability of several metabolites of C8- and C9-alkylphenol ethoxylates, including nonylphenoxyacetic acid (NPEC1), nonylphenoxyethoxyacetic acid (NPEC2), octylphenoxyacetic acid (OPEC1), octylphenoxyethoxyacetic acid (OPEC2), and nonylphenol (NP) . Using OECD method 301B (modified Sturm method), OPEC1 and OPEC2 are readily biodegradable: both compounds exceeded 60% of theoretical CO2 formation (ThCO2) by day 28, and required less than 10 days to go from 10% to 60% ThCO2 . Also using method 301B, NPEC1 and NPEC2 exceeded 60% ThCO2 at day 28, but did not meet the 10 day window . Using OECD method 301F, the manometric respirometry method that measures oxygen consumption, approximately 62% of NP was biodegraded in 28 days, but required more than 10 days to go from 10% to 60% biodegradation . While the validity of the "10-day window" is currently being debated within OECD, the data show that the common metabolites of C8- and C9-APEs are rapidly degraded in the test systems used, which strongly suggests that they would not accumulate or persist in the environment.

Chemosphere, 1999 Apr, 38(9), 1997 - 2001
An in vitro study on the toxic effects of nonylphenols (NP) in mitochondria; Bragadin M et al.; This paper is focused on alkylphenols, compounds which are formed by the biodegradation of polyethoxilatedalkylphenols detergents . Our experiments show that alkylphenols act not only as detergents, but also as uncouplers of the oxidative phosphorylation . This effect, can be observed at very low doses, thus suggesting that the preferential target of nonylphenols in living organisms are mitochondria.

Biotechnol Bioeng, 1999 Jan 5, 62(1), 1 - 11
Kinetics and modeling of autotrophic thiocyanate biodegradation; Hung CH et al.; The biokinetic parameters for autotrophic systems are difficult to obtain and are often mistakenly determined because the size of the autotrophic population in mixed (i.e., heterotrophic and autotrophic) cultures cannot be accurately estimated . This article presents a systematic approach, combining bioenergetic calculations and experimental data, to obtain values of the biokinetic parameters pertinent to the aerobic, autotrophic biodegradation of thiocyanate . Nonlinear regression techniques were employed using both initial thiocyanate utilization rate data and single thiocyanate depletion curves . Both types of data were necessary to overcome the problems arising from the linear nature of the substrate depletion curves and the high correlation of the biokinetic model parameters inherent in nonlinear regression analysis . The aerobic biodegradation of thiocyanate followed a substrate inhibition pattern that was successfully described by the Haldane-Andrews model . Although regression analysis did not yield unique biokinetic parameter estimates, the following parameter value ranges were obtained: maximum specific substrate utilization rate (k), 0.26 to 0.44 mg SCN-/mg biomass h; half-saturation coefficient (Ks), 2.3 to 7.1 mg SCN-/L; and inhibition coefficient (Ki), 28 to 109 mg SCN-/L . Based on the estimated biokinetic parameter values, a design and operation diagram was constructed that depicts the steady-state thiocyanate concentration as a function of solids retention time for a completely mixed, continuous-flow reactor .

Biotechnol Bioeng, 1998 Nov 20, 60(4), 397 - 407
Effect of nonionic surfactants on naphthalene dissolution and biodegradation; Mulder H et al.; The effect of six nonionic surfactants, Igepal CA-720, Tergitol NPX, Triton X-100, PLE4, PLE10, and PLE23, on the dissolution rate of solid naphthalene was studied in stirred batch reactors . Results showed increased mass-transfer rates with increased surfactant concentrations up to 10 kg m-3 . Dissolution experiments were adequatly described by a mechanistic mass-transfer model . Partitioning of naphthalene into the micelles and the diffusion coefficients of the micelles affected the dissolution rate most significantly . Combined dissolution and biodegradation experiments with Triton X-100 or PLE10 with naphthalene showed that the biomass-formation rate of Pseudomonas 8909N (DSM No . 11634) increased concomitantly with the mass-transfer rate under naphthalene-dissolution limited conditions up to surfactant concentrations of 6 kg m-3 .

Biotechnol Bioeng, 1998 Aug 20, 59(4), 482 - 94
Surfactant-enhanced biodegradation of high molecular weight polycyclic aromatic hydrocarbons by stenotrophomonas maltophilia
Boonchan S, Britz ML, Stanley GA.
The objectives of this study were to isolate and evaluate microorganisms with the ability to degrade high molecular weight polycyclic aromatic hydrocarbons (PAHs) in the presence of synthetic surfactants . Stenotrophomonas maltophilia VUN 10,010, isolated from PAH-contaminated soil, utilized pyrene as a sole carbon and energy source and also degraded other high molecular weight PAHs containing up to seven benzene rings . Various synthetic surfactants were tested for their ability to improve the PAH degradation rate of strain VUN 10,010 . Anionic and cationic surfactants were highly toxic to this strain, and the Tween series was used as a growth substrate . Five nonionic surfactants (Brij 35, Igepal CA-630, Triton X-100, Tergitol NP-10, and Tyloxapol) were not utilized by, and were less toxic to, strain VUN 10,010 . MSR and log Km values were determined for fluoranthene, pyrene, and benzo{a}pyrene in the presence of these nonionic surfactants and their apparent solubility was increased by a minimum of 250-fold in the presence of 10 g L-1 of all surfactants . The rate of pyrene degradation by strain VUN 10,010 was enhanced by the addition of four of the nonionic surfactants (5-10 g L-1); however, 5 g L-1 Igepal CA-630 inhibited pyrene degradation and microbial growth . The specific growth rate of VUN 10,010 on pyrene was increased by 67% in the presence of 10 g L-1 Brij 35 or Tergitol NP-10 . The addition of Brij 35 and Tergitol NP-10 to media containing a single high molecular weight PAH (four and five benzene rings) as the sole carbon source increased the maximum specific PAH degradation rate and decreased the lag period normally seen for PAH degradation . The addition of Tergitol NP-10 to VUN 10,010 cultures which contained a PAH mixture (three to seven benzene rings) substantially improved the overall degradation rate of each PAH and increased the specific growth rate of VUN 10,010 by 30% . Evaluation of the use of VUN 10,010 for degrading high molecular weight PAHs in leachates from surfactant-flushed, weathered, PAH-contaminated sites is warranted .

Biotechnol Bioeng, 1998 Apr 5, 58(1), 1 - 12
Continuous culture dynamics for aniline metabolism by Pseudomonas sp . CIT1; Thomas SM et al.; Inhibition by toxic substrates enables multiple steady states to arise in biodegradation systems . This phenomenon was investigated for the continuous metabolism of aniline by Pseudomonas sp . CIT1 . Differences of various metabolic parameters between the two growth regimes (uninhibited and inhibited) and the transient response to a step-up in dilution rate were determined . Regulatory mechanisms consistent with the experimental evidence are proposed . Aniline is the transcriptional inducer of a metabolic pathway that converts aniline to TCA cycle intermediates . The suite of enzymes is coordinately expressed from a single promoter . We followed the level of the pathway mRNA using a fragment containing the catechol 2,3 dioxygenase gene (andioxB) and monitored the pathway enzyme activity using catechol 2,3 dioxygenase (C23D) . The inhibited regime resulted in a 60% lower growth yield, near constant levels of C23D monomer, but a 50% reduction in the specific activity of C23D, increased RNA synthesis rates (total and aniline pathway mRNA), and elevated RNA decay rates . Elucidation of regulatory mechanisms indicates that C23D is noncompetitively inhibited by aniline and subject to feedback inhibition by 2-hydroxymuconic semialdehyde (HMS) . During uninhibited growth regime operation, metabolism of HMS is the rate-limiting step; in contrast, conversion of aniline to catechol limits growth in the inhibited regime .

Biotechnol Bioeng, 1998 Feb 5, 57(3), 356 - 66
Biodegradation kinetics of naphthalene in nonaqueous phase liquid-water mixed batch systems: comparison of model predictions and experimental results; Ghoshal S et al.; A model is formulated to describe dissolution of naphthalene from an insoluble nonaqueous phase liquid (NAPL) and its subsequent biodegradation in the aqueous phase in completely mixed batch reactors . The physicochemical processes of equilibrium partitioning and mass transfer of naphthalene between the NAPL and aqueous phases were incorporated into the model . Biodegradation kinetics were described by Monod's microbial growth kinetic model, modified to account for the inhibitory effects of 1,2-naphthoquinone formed during naphthalene degradation under certain conditions . System parameters and biokinetic coefficients pertinent to the NAPL-water systems were determined either by direct measurement or from nonlinear regression of the naphthalene mineralization profiles obtained from batch reactor tests with two-component NAPLs comprised of naphthalene and heptamethylnonane . The NAPLs contained substantial mass of naphthalene, and naphthalene biodegradation kinetics were evaluated over the time required for near complete depletion of naphthalene from the NAPL . Model predictions of naphthalene mineralization time profiles compared favorably to the general trends observed in the data obtained from laboratory experiments with the two-component NAPL, as well as with two coal tars obtained from the subsurface at contaminated sites and composed of many different PAHs (polycyclic aromatic hydrocarbon compounds) . The effects of varying the NAPL mass and the naphthalene mole fractions in the NAPL are discussed . It was observed that the time to achieve a given percent removal of naphthalene does not change significantly with the initial mass of naphthalene in a fixed volume of the NAPL . Significant changes in the mineralization profiles are observed when the volume (and mass) of NAPL in the system is changed .

Biotechnol Bioeng, 1998 Jan 20, 57(2), 145 - 54
Influence of hydrodynamic conditions on naphthalene dissolution and subsequent biodegradation; Mulder H et al.; The influence of hydrodynamic conditions on the dissolution rate of crystalline naphthalene as a model polycyclic aromatic hydrocarbon (PAH) was studied in stirred batch reactors with varying impeller speeds . Mass transfer from naphthalene melts of different surface areas to the aqueous phase was measured and results were modeled according to the film theory . Results were generalized using dimensionless numbers (Reynolds, Schmidt, and Sherwood) . In combined mass transfer and biodegradation experiments, the effect of hydrodynamic conditions on the degradation rate of naphthalene by Pseudomonas 8909N was studied . Experimental results were mathematically described using mass-transfer and microbiological models . The experiments allowed determination of mass-transfer and microbiological parameters separately in a single run . The biomass formation rate under mass transfer limited conditions, which is related to the naphthalene biodegradation rate, was correlated to the dimensionless Reynolds number, indicating increased bioavailability at increased mixing in the reactor liquid . The methodology presented in which mass transfer processes are quantified under sterile conditions followed by a biodegradation experiment can also be adapted to more complex and realistic systems, such as particulate, suspended PAH solids or soils with intrapartically sorbed contaminants when the appropriate mass-transfer equations are incorporated .

FEBS Lett, 1999 Mar 5, 446(1), 49 - 54
Biodegradative mechanism of the brown rot basidiomycete Gloeophyllum trabeum: evidence for an extracellular hydroquinone-driven fenton reaction; Kerem Z et al.; We have identified key components of the extracellular oxidative system that the brown rot fungus Gloeophyllum trabeum uses to degrade a recalcitrant polymer, polyethylene glycol, via hydrogen abstraction reactions . G . trabeum produced an extracellular metabolite, 2,5-dimethoxy-1,4-benzoquinone, and reduced it to 2,5-dimethoxyhydroquinone . In the presence of 2,5-dimethoxy-1,4-benzoquinone, the fungus also reduced extracellular Fe3+ to Fe2+ and produced extracellular H2O2 . Fe3+ reduction and H2O2 formation both resulted from a direct, non-enzymatic reaction between 2,5-dimethoxyhydroquinone and Fe3+ . Polyethylene glycol depolymerization by G . trabeum required both 2,5-dimethoxy-1,4-benzoquinone and Fe3+ and was completely inhibited by catalase . These results provide evidence that G . trabeum uses a hydroquinone-driven Fenton reaction to cleave polyethylene glycol . We propose that similar reactions account for the ability of G . trabeum to attack lignocellulose.

Semin Vasc Surg, 1999 Mar, 12(1), 83 - 91
Structural failure of Dacron arterial grafts; Nunn DB; The ultimate test of a Dacron (polyethylene terephthalate or PET) arterial prosthesis depends on its ability to retain sufficient strength and durability to function properly for the life of the patient . Because graft recipients appear to be living longer, primarily because of improved medical and surgical treatment of cardiovascular disease, strength and durability of arterial prostheses have become increasingly important . From the time of implantation, all PET prostheses are continuously subjected to the cyclic stresses of pulsatile blood flow with mechanical fatiguing of yarns, as well as chemical and physical alterations associated with biodegradation . Notwithstanding the overall successful use of currently available prostheses, structural failure continues to occur sporadically and is especially noteworthy because of its potentially serious nature and usual occurrence 5 or more years after implantation, when the diagnosis may be overlooked or delayed . A review of the subject is provided based on the premise that timely recognition and appropriate management require a basic understanding of PET prostheses with respect to various fabric constructions and physical properties, graft healing, postoperative dilation, and known causes of structural failure.

Semin Vasc Surg, 1999 Mar, 12(1), 46 - 51
Biological vascular grafts; Wengerter K et al.; Biological bypass graft material has been used as an alternative to autogenous vein since the first lower extremity revascularization procedures were performed . Both immunogenicity and biodegradation can contribute to the failure of these grafts and must be addressed . Cryopreservation at ultralow temperatures (-196 degrees C) after pretreatment with dimethylsulfoxide has been successful in preserving viable vein graft endothelium . Both rejection and deterioration of the cellular elements may contribute to the relatively high failure rates . The umbilical vein graft has become an effective alternative to autogenous material . The glutaraldehyde tanning procedure increases tensile strength, masks antigenicity, and sterilizes the tissue . Recent results with excellent 5-year patency (67%) and cumulative limb salvage (80%) confirm the utility of this graft.

J Biomater Sci Polym Ed, 1999, 10(1), 79 - 94
Neovascularization effect of biodegradable gelatin microspheres incorporating basic fibroblast growth factor; Tabata Y et al.; Biodegradable microspheres were prepared through glutaraldehyde cross-linking of gelatin without using any surfactants as a carrier matrix of basic fibroblast growth factor (bFGF) . In the in vitro system, bFGF was sorbed to microspheres of acidic gelatin with an isoelectric point (IEP) of 5.0, but not to those of basic gelatin with an IEP of 9.0 . The rate of bFGF sorption to the acidic gelatin microsphere in phosphate-buffered saline solution (pH 7.4) was smaller than that in water . Following incorporation of bFGF into the microspheres at 4 degrees C for 12 h, bFGF release from the bFGF-incorporating microspheres was studied . Approximately 30% of incorporated bFGF was released from the acidic gelatin microsphere within the initial 3 h, followed by no substantial release, whereas the basic gelatin microsphere released almost completely the incorporated bFGF within 1 day . It is likely that when basic bFGF molecules were immobilized to the acidic gelatin constituting microspheres through polyion complexation, they were not readily released under the in vitro nondegradation condition of gelatin . Incorporation of anionic carboxylmethyl cellulose (CMC) into the acidic gelatin microspheres reduced the amount of bFGF desorbed initially . This indicates that the initial burst is ascribed to free bFGF which is not ionically interacted with the acidic gelatin . CMC will function as a bFGF sorbent to suppress the initial leakage from the microspheres . When injected subcutaneously into the mouse back, bFGF-incorporating acidic gelatin microspheres were degraded over time and induced neovascularization around the injection site, in marked contrast to bFGF in the solution form . CMC incorporation slowed down the biodegradation and vascularization effect of bFGF-incorporating gelatin microspheres . It was concluded that the gelatin microsphere was a promising carrier matrix of bFGF to enhance the vascularization effect.

Appl Microbiol Biotechnol, 1999 Feb, 51(2), 125 - 33
Compostable packaging materials--test methods and limit values for biodegradation; Pagga U; In order to classify packaging materials as capable of organic recovery according to the packaging regulation of the European Union, the intended materials must be tested for their compostability . An important prerequisite is the determination of biodegradability by standardized test methods . Details of the intended tests are not comprehensible without further knowledge of the problems of biodegradation testing . The test methods and the limit values used to evaluate the biodegradation results are presented and discussed against the background of established test methods and limit values for chemicals . Furthermore the problem of ecotoxicity tests in connection with compost quality is discussed and an overview of European test laboratories is given.

Acta Crystallogr D Biol Crystallogr, 1999 Apr, 55 ( Pt 4), 901 - 3
Crystallization and preliminary crystallographic analysis of the hydroxyquinol 1,2-dioxygenase from Nocardioides simplex 3E: a novel dioxygenase involved in the biodegradation of polychlorinated aromatic compounds; Benvenuti M et al.; Hydroxyquinol 1,2-dioxygenase (HQ1,2O) from Nocardioides simplex 3E, an enzyme involved in the aerobic biodegradation of a large class of chloroaromatic compounds such as 2,4-dichlorophenoxyacetate (2,4-D) and 2,4,5-trichlorophenoxyacetate (2,4,5-T), has been crystallized . HQ1,2O, which specifically catalyzes the intradiol cleavage of hydroxyquinol (1,2,4-trihydroxybenzene), an intermediate in the degradation of a variety of aromatic pollutants, to maleylacetate, has been recently purified to homogeneity . The enzyme is an homodimer composed of two identical subunits in a alpha 2-type quaternary structure, has a molecular weight of about 65 kDa and contains a catalytically essential Fe(III) ion . Crystals of HQ1,2O obtained using 2% PEG 400 and 2 M ammonium sulfate at pH 7.5 as precipitants belong to the orthorhombic space group P212121, with unit-cell parameters a = 81.15 (6), b = 86.79 (7), c = 114.93 (8) . Assuming one dimer per asymmetric unit, the Vm value is 2.51 A3 Da-1 . A complete native data set to 1.8 A resolution has been collected on a laboratory source . This is the first intradiol dioxygenase which specifically catalyzes the cleavage of hydroxyquinol to give diffraction-quality crystals.

Biomed Mater Eng, 1998, 8(5-6), 335 - 42
Improvement of the friction behaviour of NiTi orthodontic archwires by nitrogen diffusion; Gil FJ et al.; The lack of low friction coefficient for the NiTi superelastic archwires makes difficult the optimal use of these materials in orthodontic applications . In this study, the decrease of this friction coefficient has been achieved by means of nitrogen diffusion heat treatments . The titanium nitride coating has been characterised by means of optical and scanning electron microscopy . Transformation temperatures, critical stresses, hardness and friction coefficient have been determined . Besides, the metallic ion release studies showed that the titanium nitride coating prevents biodegradation.

Contact Dermatitis, 1999 Mar, 40(3), 146 - 9
Does sodium lauryl sulfate concentration vary with time?
Sugar M, Schnetz E, Fartasch M.
When performing skin irritation tests with sodium lauryl sulfate (SLS), the quality of the test solution is of major importance for the reproducibility and comparability of the results . The influence of 4 different storage parameters (concentration, duration, temperature, material of the storage vials) on the stability of aqueous SLS solutions was investigated under non-sterile conditions . SLS solutions at 5 different concentrations (0.001%, 0.01%, 0.1%, 0.5%, 1%) were analysed by mobile phase ion chromatography . Analyses were performed after a storage time of 3 h, 1 week, and 4 weeks . Storage was carried out at different temperatures: -18 degrees C, 6 degrees C, and 23 degrees C . The storage containers were of 2 different materials (glass and polypropylene) . After a storage of 1 week, no decrease in SLS concentration was observed, regardless of the chosen conditions . After 4 weeks at 6 degrees C and 23 degrees C, the SLS concentration was found to be significantly decreased for the 2 lowest concentrations (0.001% and 0.01%) . At higher concentrations and lower temperatures, no decrease in SLS concentration had occurred . In parallel to the loss of SLS, contamination with bacteria was found in the solutions, especially at the 2 lowest concentrations . Bacterial growth was not observed at higher concentrations . The possibility of biodegradation of SLS has to be taken into account, especially when dealing with low concentrations of SLS.

Chemosphere, 1999 Mar, 38(6), 1391 - 400
A kinetic distribution model of evaporation, biosorption and biodegradation of polychlorinated biphenyls (PCBs) in the suspension of Pseudomonas stutzeri; Dercova K et al.; Kinetics of distribution of PCBs in an active bacterial suspension of Pseudomonas stutzeri was studied by monitoring the evaporated amounts and the concentration remaining in the liquid medium with the biomass . To determine the biodegradation rate constants of the individual congeners of the PCB formulation Delor 103, a model considering biosorption, evaporation, and primary biodegradation constructed previously was used . Rate constants of biodegradation imply that biodegradation of individual congeners is structure-dependent process . Biodegradability decreases with increasing number of chlorine substituents in the molecule, especially if they are in the ortho and para positions . On the other hand, the increasing number of free ortho and meta positions in the biphenyl molecule leads to better biodegradability . For a simple empirical determination of the influence of the chlorine substitution pattern on biodegradability, the di- and trichlorobiphenyl rate constants of biodegradation were analysed.

Chemosphere, 1999 Mar, 38(6), 1339 - 46
Laboratory simulation of biodegradation of chemicals in surface waters: closed bottle and respirometric test; Gotvajn AZ et al.; Microbial degradation is the most dominant elimination mechanism of organics from the environment . For evaluation of biodegradability of pure chemicals many standardized tests are available, but no standardized procedure for assessment of biodegradability of chemicals in surface water is agreed upon . Rates of in-situ biodegradation are usually estimated in laboratory simulation where environmental factors are reproduced to some extent . The aim of our study was to compare standardised ready biodegradability assessment, test (Closed bottle test) and its modifications employing the basic agreements on test conditions to simulate biodegradation in surface water . Standard test was modified using various natural river waters to simulate the natural environment in a simplified way . The impact of different types and amounts of nutrients and microorganisms on biodegradation was confirmed . The conditions in the recipient should be examined to extrapolate the results from ready biodegradability tests to real surface water.

Urol Nefrol (Mosk), 1998 Nov-Dec, (6), 7 - 8
{Effects of hyperbaric oxygenation on oxidative phosphorylation in post-nephrotomy tissues sutured with different surgical threads (an experimental study)}; Kostenko VA; The activity of mitochondrial respiration and oxidative phosphorylation (OP) was studied in white rats subjected to nephrotomy . The suture was made with absorbable surgical threads such as catgut plain, biofil (from dura mater spinalis of the cattle), dexon II (polyglycolic acid) . The use of catgut plain inhibits biosynthetic processes 7 and 14 days after operation . Hyperbaric oxygenation enhances oxidative phosphorylation in postoperative renal tissue sutured with different biological and synthetic absorbable surgical threads (catgut, biofil, dexon II) and prevents sharp depression of the above processes in the course of catgut biodegradation . This fact is of great importance for reduction of normal functional and metabolic activity of the operated kidney.

Chemosphere, 1999 Feb, 38(5), 1175 - 88
Aerobic biodegradation of dichloroethylenes in surface and subsurface soils; Klier NJ et al.; Laboratory studies were conducted to examine the aerobic biodegradation of dichloroethylenes (cis-1,2-DCE, trans-1,2-DCE and 1,1-DCE) in soil and groundwater . Authentic surface and subsurface materials with no reported DCE exposure history were used . All DCE isomers were observed to biodegrade to varying degrees in the soils examined . Use of radiolabeled {14C} test chemicals allowed correlation of DCE disappearance with mineralization to 14CO2 . Study results indicate that naturally occurring microorganisms in soil and groundwater are capable of degrading cis-1,2-, trans-1,2- and 1,1-DCE without laboratory supplementation of exogenous organic nutrients, or previous exposure history . The data further suggest that degradative potential may vary with soil type, DCE isomer structure, and concentration.

Chemosphere, 1999 Feb, 38(5), 1157 - 64
Involvement of bioemulsifier in heptadecane uptake in Pseudomonas nautica; Patricia B et al.; A microbial surfactant was investigated for its potential to enhance the biodegradation of heptadecane . The bioemulsifier used in this study was extracted from culture supernatants of Pseudomonas nautica after growth on heptadecane . The heptadecane uptake rate-could be increased 15-fold by the addition of 1.5 mg protein of bioemulsifier per 100 mg of heptadecane . Scanning electron microscopy showed that bioemulsification was the main mode allowing the transfer of hydrocarbon in the presence of the isolated compound.

Vet Clin North Am Small Anim Pract, 1999 Jan, 29(1), 161 - 91, xii-xiii
Canine urate urolithiasis . Etiopathogenesis, diagnosis, and management; Bartges JW et al.; Etiopathologic factors predisposing to urate lithogenesis in Dalmatian and non-Dalmatian dogs represent diverse pathologic and/or physiologic processes involving purine nucleotide and ammonia synthesis, biodegradation, and excretion . Predisposing factors for urate urolith formation include hyperuricemia, hyperammonemia, hyperuricosuria, hyperammonuria, aciduria, and genetic predisposition . Medical therapy of dogs forming urate uroliths should be directed at modifying these predisposing factors through dietary modification, administration of allopurinol, and/or surgical correction of portovascular anomalies if present . The precise mechanisms resulting in urate urolith formation in dogs have not been determined.

Artif Organs, 1999 Feb, 23(2), 186 - 94
The merit of sintered PDLLA/TCP composites in management of bone fracture internal fixation; Lin FH et al.; Polyesters based on lactic acid have been reported in terms of safety and biodegradation in human beings for 2 decades . The greatest advantage of such material is its degradation conducted only by hydrolysis, whereby the ester backbones are supposed to be unchained in the aqueous condition . The final degradable products are carbon dioxide and water which can be metabolized and digested in the physiological environment . The goal of this study was aimed at developing a composite sintered with poly-DL-lactide (PDLLA) and tricalcium phosphate (TCP) ceramic particles for orthopedic application . The TCP particles in a range of 30-60 wt% with 5 wt% increments were doped into the PDLLA matrix which was prepared by melting and hot pressing techniques for the reinforcement . The basic mechanical strength, biodegradable behavior, and biological response of the composites were investigated in the study . Various techniques such as pH meter, UV, Fourier-transform infrared, and x-ray diffractometer were used to examine and record the degradable process of the composites soaked in saline for 1-16 weeks . The rabbit femur condyle fracture fixation test was used to evaluate tissue compatibility and the effects of bone fracture fixation on the composites . Histological observation and x-ray photography were used for investigating assistance . The mechanical strength of the composites initially increased with TCP additions up to 50wt%, but thereafter they showed no significant difference (p < 0.05) . The composite with 50 wt% TCP addition showed greater mechanical strength and had good agreement with cortical bone in terms of its elastic modulus of 30-40 GPa . The weight loss of the pure PDLLA soaked in the saline started at 4 weeks and reached 95% after 16 weeks . The composites compared with pure PDLLA, however, showed no apparent evidence of degradation after soaked for 12 weeks . The possible mechanisms for the delayed degradation of the composites in saline might have been solution penetration retardation by the ceramic particles and chemical bonds formed between the interface of the TCP particles and the PDLLA matrix . In the histological evaluation of the rabbit femur condyle fracture fixation test, the surface of the composite with 50 wt% TCP addition was attached by the newly generated bone without fibrous tissue around 8 weeks after implantation . The fractured bone was gradually healed and the composite firmly and properly fixed on the fracture area during the implanted period, which provided a breeding environment for normal bone remodeling . The developed composite was thought to be an alternative material for orthopedic application in the future, especially for bone screws and bone plates.

Int J Artif Organs, 1998 Dec, 21(12), 814 - 9
Surface modification of polyurethane heart valves: effects on fatigue life and calcification; Bernacca GM et al.; Polyurethane heart valves can be functionally durable with minimal calcification, in vitro . In vivo, these characteristics will depend on the resistance of the polyurethane to thrombogenesis and biodegradation . Surface modification may improve the polyurethane in these respects, but may adversely affect calcification and durability . This study investigates the effects of surface modifications of two polyurethane heart valves (PEU and PEUE) on their in vitro fatigue and calcification behaviour . Modifications included heparin, taurine, 3-aminopropyltriethoxysilane and polyethylene oxide (PEO) . Neither hydrodynamic function nor leaflet thickness distribution was significantly altered by surface modification . PEO-modification was detrimental to valve fatigue durability and calcification . Heparin, taurine or aminosilane modifications of PEU valves increased durability . Aminosilane modification of PEUE valves increased durability compared with PEO modification . Appropriate surface modification may be useful to improve blood compatibility of implantable polyurethanes, and may also be advantageous as regards fatigue durability of flexing materials in longterm applications.

J Biotechnol, 1999 Jan 8, 67(1), 13 - 32
Lipophilic compounds in biotechnology--interactions with cells and technological problems; Angelova B et al.; Lipophilic compounds are of significant importance in modern biotechnology . Centerly of interest are the biodegradation as well as the biotransformation of such lipophilic and often water-immiscible substances . Both whole cells and/or enzymes are used for these processes . It is obvious that a wide range of problems arise in an application of such complex systems consisting of biocatalysts substrate(s), product(s), water, (in some cases water-immiscible organic solvents): (i) interactions between lipophilic compounds and the membranes resulting in the change of some physiological characteristics of the living system; (ii) problems in the transport of these compounds (substrates and/or products) within the complex structured reaction systems; (iii) the problem of increasing the solubility of the lipophilic and mostly water-immiscible compounds with a minimum of inhibition effects on the processes; (iv) the presence of lipophilic components may also cause changes of the transport processes within the system (e.g . immobilized cells) resulting in changed yield or activity of the biological system . These problems are critically discussed in this review in relation to the known modes of interaction of lipophilic compounds with membranes, the bioavailability of the substrates, and the cases of steroid biotransformations . An outlook of future aspects in research, development and application of such processes is given.

Morphologie, 1998 Sep, 82(258), 3 - 9
{Biomaterials in an osteo-articular environment . Report of 129 anatomoclinical cases}; Adnet JJ et al.; Actually, there is a range of biomaterials which are synthetic or metallic (or the both) . They are employed as prosthesis (biostability property) or as bone graft (bioresorbability property) . To understand the interactions between cells and such materials, we studied with human bone cellular cultures the cytologycal, immunohistochemical, cytogenetical and ultrastructural aspects of biomaterials in cell cultures . This paper concerns bioceramics like Pyrost, coral, biosorb, oxbone and polymers like polyethylene and silicones . The aim of this work is to evaluate the efficiency of some biomaterials . We found that porosity is primordial to promote biodegradation of bone substitutes . In fact, the biomaterials is integrated and lead to an osteoconduction, an osteoformation and finally an osteoinduction . Our observations show the implant resorption and ossification occurring in the matrix which penetrate it.

J Biomater Appl, 1999 Jan, 13(3), 187 - 205
Synthesis of cholesterol esterase by monocyte-derived macrophages: a potential role in the biodegradation of poly(urethane)s; Labow RS et al.; Many studies have described the role of monocyte-derived macrophages (MDM) in inflammation leading to atherosclerosis, a process in which alterations in the metabolism of cholesterol esters is well established . On the other hand, the mechanism of MDM activation in response to biomaterial surfaces is still not well understood . Several studies have described the different degrees of activation of monocytes on poly(urethane) surfaces by measuring the release of early markers of differentiation, such as cytokines . It has been possible to decrease MDM activation in contact with materials by modifying the material surface with antioxidants . Therefore, it has been proposed that it is the reactive oxygen species provided by MDM which are responsible for deleterious effects observed in material-derived inflammation . A recent study has shown that one of the markers of the degree of differentiation of MDM is the synthesis of cholesterol esterase (CE), an enzyme demonstrated as causing biodegradation of polyester(urethane)s and more recently polyether- and polycarbonate-poly(urethane)s as well . In this review article, markers used to assess MDM differentiation on material surfaces will be described and related to the activation of MDM . In particular, the CE accumulation in MDM which is associated with atherosclerosis will be related to its degradative potential during chronic inflammation . How this may impact on the biostability of implanted poly(urethane) medical devices is discussed.

Arch Orthop Trauma Surg, 1998, 118(3), 149 - 55
Tissue response to bioabsorbable self-reinforced polylevolactide and polyglycolide pins implanted intra-articularly and directly into the bone on different levels . An experimental study on rats; Koskikare K et al.; Self-reinforced poly-L-lactide (SR-PLLA) and self-reinforced polyglycolide (SR-PGA) pins were implanted intra-articularly and directly into the bone of the distal femur of rats at three levels: above, on the same level, and under the surface . For the controls only channels were drilled, or the controls were not operated at all . The follow-up times were 3, 6, and 12 weeks for SR-PGA and 3, 6, 12, and 24 weeks for SR-PLLA . The macroscopic appearance and histologically the villus reaction, the mononuclear phagocytosis and giant cells, the neutrophils, the lymphocytes, the plasma cells, the eosinophils, and the mast cells were analyzed . In the histologic analysis, the most favorable implantation depth was found to be under the surface where the contact between the implants and bone was best, and the orifice was covered with new trabecular bone at 3 weeks . This was especially seen in intra-articular implantation . In general, the tissue responses were mild, and could also be explained in the statistical analysis by a normal postoperative tissue response and faster biodegradation of PGA.

Appl Environ Microbiol, 1999 Feb, 65(2), 529 - 33
Anaerobic benzene biodegradation linked to nitrate reduction; Burland SM et al.; Benzene oxidation to carbon dioxide linked to nitrate reduction was observed in enrichment cultures developed from soil and groundwater microcosms . Benzene biodegradation occurred concurrently with nitrate reduction at a constant ratio of 10 mol of nitrate consumed per mol of benzene degraded . Benzene biodegradation linked to nitrate reduction was associated with cell growth; however, the yield, 8.8 g (dry weight) of cells per mol of benzene, was less than 15% of the predicted yield for benzene biodegradation linked to nitrate reduction . In experiments performed with {14C}benzene, approximately 92 to 95% of the label was recovered in 14CO2, while the remaining 5 to 8% was incorporated into the nonvolatile fraction (presumably biomass), which is consistent with the low measured yield . In benzene-degrading cultures, nitrite accumulated stoichiometrically as nitrate was reduced and then was slowly reduced to nitrogen gas . When nitrate was depleted and only nitrite remained, the rate of benzene degradation decreased to almost zero . Based on electron balances, benzene biodegradation appears to be coupled more tightly to nitrate reduction to nitrite than to further reduction of nitrite to nitrogen gas.

Appl Environ Microbiol, 1999 Feb, 65(2), 431 - 7
Degradation of starch-poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) bioplastic in tropical coastal waters; Imam SH et al.; Extruded bioplastic was prepared from cornstarch or poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (PHBV) or blends of cornstarch and PHBV . The blended formulations contained 30 or 50% starch in the presence or absence of polyethylene oxide (PEO), which enhances adherence of starch granules to PHBV . Degradation of these formulations was monitored for 1 year at four stations in coastal water southwest of Puerto Rico . Two stations were within a mangrove stand . The other two were offshore; one of these stations was on a shallow shoulder of a reef, and the other was at a location in deeper water . Microbial enumeration at the four stations revealed considerable flux in the populations over the course of the year . However, in general, the overall population densities were 1 order of magnitude less at the deeper-water station than at the other stations . Starch degraders were 10- to 50-fold more prevalent than PHBV degraders at all of the stations . Accordingly, degradation of the bioplastic, as determined by weight loss and deterioration of tensile properties, correlated with the amount of starch present (100% starch >50% starch > 30% starch > 100% PHBV) . Incorporation of PEO into blends slightly retarded the rate of degradation . The rate of loss of starch from the 100% starch samples was about 2%/day, while the rate of loss of PHBV from the 100% PHBV samples was about 0.1%/day . Biphasic weight loss was observed for the starch-PHBV blends at all of the stations . A predictive mathematical model for loss of individual polymers from a 30% starch-70% PHBV formulation was developed and experimentally validated . The model showed that PHBV degradation was delayed 50 days until more than 80% of the starch was consumed and predicted that starch and PHBV in the blend had half-lives of 19 and 158 days, respectively . Consistent with the relatively low microbial populations, bioplastic degradation at the deeper-water station exhibited an initial lag period, after which degradation rates comparable to the degradation rates at the other stations were observed . Presumably, significant biodegradation occurred only after colonization of the plastic, a parameter that was dependent on the resident microbial populations . Therefore, it can be reasonably inferred that extended degradation lags would occur in open ocean water where microbes are sparse.

Rev Environ Contam Toxicol, 1999, 159, 41 - 93
Microbial methods for assessing contaminant effects in sediments; Eismann F et al.; Contaminated sediments influence drastically the long-term toxicological and ecological properties of aquatic ecosystems . During the past three decades, scientific knowledge about sediment-water exchange processes and the deposition and distribution of pollutants in water and sediment phases has been supplemented by extensive research on the effects of sediment-associated pollutants on aquatic organisms . Basic research in microbiology, ecology, and toxicology has uncovered the crucial role of sediment microorganisms for the biodegradation of organic matter and for the cycling of nutrients, as well as the susceptibility of these processes to toxic pollution events . Microorganisms have been extensively applied in aquatic toxicology, and various microbial toxicity tests are today available that successfully couple microbial toxicity endpoints to the specificity of the sediment matrix . Sediment-associated toxicants can be brought in contact with test bacteria using sediment pore waters, elutriates, extracts, or whole-sediment material . Toxicity indication principles for microorganisms are versatile and comprise growth and biomass determinations, respiration or oxygen uptake, bacterial luminescence, the activity of a variety of enzymes, and a compendium of genotoxicity assays . The border between toxicological and ecological contaminant effect evaluations in sediments is flexible, and long-term ecological predictions should also include an assessment of pollutant degradation capacities and of key reactions in element cycling . Evaluating microbial community structure and function in environmental systems makes use of modern molecular techniques and bioindicators that could trigger a new quality in the assessment of contaminated sediments in terms of indication of subtoxic effects and early-warning requirements.

Bioinformatics, 1998, 14(9), 803 - 6
Representing metabolic pathway information: an object-oriented approach; Ellis LB et al.; MOTIVATION: The University of Minnesota Biocatalysis/Biodegradation Database (UM-BBD) is a website providing information and dynamic links for microbial metabolic pathways, enzyme reactions, and their substrates and products . The Compound, Organism, Reaction and Enzyme (CORE) object-oriented database management system was developed to contain and serve this information . RESULTS: CORE was developed using Java, an object-oriented programming language, and PSE persistent object classes from Object Design, Inc . CORE dynamically generates descriptive web pages for reactions, compounds and enzymes, and reconstructs ad hoc pathway maps starting from any UM-BBD reaction . AVAILABILITY: CORE code is available from the authors upon request . CORE is accessible through the UM-BBD at: labmed.umn.edu/umbbd/index.html.

Biomaterials, 1999 Jan, 20(1), 27 - 34
Biocompatibility studies of anionic collagen membranes with different degree of glutaraldehyde cross-linking; Goissis G et al.; The work describes the biocompatibility and biodegradation studies of anionic collagen membranes casted form collagen gels collagen, that were selective hydrolyzed at the carboxyamide groups, as a function of the degree of cross-links induced by glutaraldehyde . Independently from the degree of cross-links, all membranes studied were characterized by a similar inflammatory response, inversely dependent on glutaraldehyde reaction time, that decreased from the time of the implant . Cell alterations, mineralization or contact necrosis were not observed in any of the membranes studied . Rates for membrane tissue biodegradation were directly related to glutaraldehyde reaction time, and ranged from 30 to periods longer than 60 days, associated with good biocompatibility . Although other properties must be considered, their use in the treatment of periodontal diseases, the biological behavior observed with the 8 h GA cross-linked membrane suggests that, anionic collagen membrane described in this work may be of potential use, not only in association with guided tissue regeneration technique for periodontal tissue reconstruction, but also in other collagen biomaterial applications where controlled biodegradability is required.

Arch Environ Contam Toxicol, 1999 Feb, 36(2), 146 - 51
Biodegradation and ecotoxicity of HFCs and HCFCs; Berends AG et al.; Hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) are used or developed as substitutes for fully halogenated chlorofluorocarbons . Based on the results of closed-bottle tests, the biodegradation of HFC-32, HCFC-123, HCFC-124, HFC-125, HFC-134a, HCFC-141b, HCFC-225ca, and HCFC-225cb was less than 60% after 28 days and therefore these compounds are considered not readily biodegradable . Standard acute toxicity tests with HCFC-123, HCFC-141b, and HCFC-225ca using algae, water fleas, and fish revealed EC50 values in the range of 17-126 mg/L . EC50 values of HFC-134a ranged between 450-980 mg/L . Fish studies with HCFC-141b and HCFC-225ca revealed bioaccumulation factors of <3 and 15-64, respectively . A study with plants revealed no effect of HCFC-141b on seed germination and growth of wheat (Triticum aestivum), radish (Raphanus sativus), and cress (Lepidium sativum) . In conclusion, HFCs and HCFCs are not very toxic to aquatic organisms and terrestrial plants . No evidence for any aerobic biodegradation for most of the HFCs and HCFCs was found.

J Vasc Surg, 1999 Jan, 29(1), 168 - 76
Polyurethane vascular prostheses decreases neointimal formation compared with expanded polytetrafluoroethylene; Jeschke MG et al.; PURPOSE: Synthetic grafts have been increasingly used for complex vascular reconstructions in patients with limited autologous vein availability . Materials currently in use induce increased stenosis and graft thrombosis compared with autologous vein, especially in smaller vessels . We examined whether grafts constructed of a porous biodegradation-resistant polycarbonate polyurethane (PU) exert better biocompatibility in terms of faster endothelialization and decreased chronic proliferation of intimal cells compared with expanded polytetrafluoroethylene (ePTFE) . METHODS: PU or ePTFE interposition grafts were implanted into the abdominal aortas of male Sprague-Dawley rats (PU, n = 37; ePTFE, n = 32) . Grafts were removed at days 1, 7, 14, 28, and 56 and 6 months and were evaluated by immunohistochemical, electron microscopic, and morphometric techniques . Bromodeoxyuridine (BrdU) was injected at 1 and 24 hours before death to determine cellular proliferation . Endothelial cells and smooth muscle cells were identified with antibodies to von Willebrand factor and alpha-actin, respectively . RESULTS:The luminal surface of PU grafts took 4 weeks to completely endothelialize, whereas ePTFE grafts took 24 weeks (P <.05) . Neointimal cell proliferation was lower in PU grafts compared with ePTFE at 56 days (1.4 +/- 0.1 versus 8.6 +/- 1.5, P <.001) and at 6 months (0.15 +/- 0.002 versus 3.4 +/- 0.5, p <.001) . Neointimal thickness at 6 months after implantation was 3.2 +/- 0.8 micrometer for PU compared with 10.3 +/- 3.1 micrometer for ePTFE (P <.05) . CONCLUSION: Polycarbonate polyurethane small vascular prostheses promoted faster luminal endothelialization, induced less chronic intimal proliferation, and produced a significantly thinner neointima than ePTFE grafts . These findings suggest that aliphatic-polycarbonate urethanes may offer advantages over standard materials such as ePTFE for vascular graft construction.

Bioorg Med Chem, 1998 Nov, 6(11), 2161 - 9
The early oxidative biodegradation steps of residual kraft lignin models with laccase; Crestini C et al.; A number of model compounds resembling the fundamental bonding patterns of residual kraft lignin, including a series of stilbenes, were incubated with laccase from Trametes versicolor in the presence and absence of delignification 'mediators' ABTS and HBT . The condensed kraft lignin model compounds seem to undergo initial degradation by laccase mainly via benzylic oxidation, demethylation and hydroxylation reactions . Phenolic 5-5', diphenylmethane and alpha-5 lignin models were found to be degraded mainly via side-chain oxidation reactions . Among the models studied, a phenolic stilbene was found to be the most reactive, yielding several products showing side-chain oxidation/transposition, demethoxylation and hydroxylation reactions . Non-phenolic 5-5', diphenylmethane and stilbene model compounds were found unreactive even in the presence of the laccase-mediator system.

Mund Kiefer Gesichtschir, 1998 Nov, 2(6), 288 - 308
{Absorbable and bioconvertible osteosynthesis materials in maxillofacial surgery}; Obwegeser JA; In order to overcome the need for secondary intervention to remove metallic osteosynthesis devices after fracture healing, endeavours have been directed towards developing resorbable osteosynthesis materials during the last decade . The resorbable material must fulfil a number of basic demands . For example, an adequate holding strength of these materials is essential for undisturbed fracture union, complete resorption after bone healing, good histocompatibility without any damage to the surrounding tissues and without detrimental distant effects within the organism . Suggested materials are primarily high-polymerlactic acid or glycolic acid compounds . In particular, research was concentrated on the enhancement of the mechanical properties and biodegradation of polylactides . Debris high in crystallin was found to be responsible for late soft tissue reactions . To achieve disintegration products with lower crystallin content stereocopolymeres of lactic acids are preferred nowadays . Based on our experimental work, another osteosynthesis system manufactured from autoclaved allogenic bone tissue was developed as an alternative . This has osteoconductive properties and converts by creeping substitution into bone . In contrast to metallic plates and screws, the modulus of elasticity is quite similar to vital bone tissue . The initial strength enables its use in the field of maxillofacial surgery.

Appl Environ Microbiol, 1999 Jan, 65(1), 163 - 8
Bacterial adhesion to soil contaminants in the presence of surfactants
Stelmack PL, Gray MR, Pickard MA.
It has been proposed that addition of surfactants to contaminated soil enhances the solubility of target compounds; however, surfactants may simultaneously reduce the adhesion of bacteria to hydrophobic surfaces . If the latter mechanism is important for the biodegradation of virtually insoluble contaminants, then the use of surfactants may not be beneficial . The adhesion of a Mycobacterium strain and a Pseudomonas strain, isolated from a creosote-contaminated soil, to the surfaces of highly viscous non-aqueous-phase liquids (NAPLs) was measured . The NAPLs were organic material extracted from soils from two creosote-contaminated sites and two petroleum-contaminated sites . Cells suspended in media with and without surfactant were placed in test tubes coated with an NAPL, and the percentages of cells that adhered to the surface of the NAPL in the presence and absence of surfactant were compared by measuring optical density . Test tubes without NAPLs were used as controls . The presence of either Triton X-100 or Dowfax 8390 at a concentration that was one-half the critical micelle concentration (CMC) inhibited adhesion of both species of bacteria to the NAPLs . Both surfactants, when added at concentrations that were one-half the CMCs to test tubes containing previously adhered bacteria, also promoted the removal of the cells from the surfaces of the NAPL-coated test tubes . Neither surfactant was toxic to the bacteria . Further investigation showed that a low concentration of surfactant also inhibited the growth of both species on anthracene, indicating that the presence of a surfactant resulted in a reduction in the uptake of the solid carbon source.

J Biol Chem, 1998 Dec 25, 273(52), 34887 - 95
Molecular basis for the stabilization and inhibition of 2, 3-dihydroxybiphenyl 1,2-dioxygenase by t-butanol; Vaillancourt FH et al.; The steady-state cleavage of catechols by 2,3-dihydroxybiphenyl 1, 2-dioxygenase (DHBD), the extradiol dioxygenase of the biphenyl biodegradation pathway, was investigated using a highly active, anaerobically purified preparation of enzyme . The kinetic data obtained using 2,3-dihydroxybiphenyl (DHB) fit a compulsory order ternary complex mechanism in which substrate inhibition occurs . The Km for dioxygen was 1280 +/- 70 microM, which is at least 2 orders of magnitude higher than that reported for catechol 2,3-dioxygenases . Km and Kd for DHB were 22 +/- 2 and 8 +/- 1 microM, respectively . DHBD was subject to reversible substrate inhibition and mechanism-based inactivation . In air-saturated buffer, the partition ratios of catecholic substrates substituted at C-3 were inversely related to their apparent specificity constants . Small organic molecules that stabilized DHBD most effectively also inhibited the cleavage reaction most strongly . The steady-state kinetic data and crystallographic results suggest that the stabilization and inhibition are due to specific interactions between the organic molecule and the active site of the enzyme . t-Butanol stabilized the enzyme and inhibited the cleavage of DHB in a mixed fashion, consistent with the distinct binding sites occupied by t-butanol in the crystal structures of the substrate-free form of the enzyme and the enzyme-DHB complex . In contrast, crystal structures of complexes with catechol and 3-methylcatechol revealed relationships between the binding of these smaller substrates and t-butanol that are consistent with the observed competitive inhibition.

J Biomed Mater Res, 1998 Winter, 43(4), 462 - 8
Interface strength studies of calcium phosphate ceramic coated strain gauges; Battraw GA et al.; In vivo strain gauging has been used to understand physiological loading and bone remodeling . In early studies, a cyanoacrylate adhesive was used to bond gauges to bone, even though this adhesive is susceptible to biodegradation that results in rapid debonding . Calcium phosphate ceramic (CPC) coated gauges have been successfully bonded to bone for long periods . However, earlier studies noted occasional debonding of coatings from gauges . The goals of this project were to develop a technique to securely bond particles to gauge backings and develop an in vitro test and assess its accuracy in simulating in vivo degradation of this interface . Gauges were heated for different time intervals, roughened with carbide papers, and prepared using layered coatings of polysulfone and CPC particles that varied in size, shape, and crystallinity . They were soaked in solution or placed in muscle pouches of rats for up to 16 weeks . They were then epoxied to fixtures, mounted on an MTS machine, and loaded to failure . Heating and roughening gauge surfaces increased the interface strengths by up to 2000% . In vivo and in vitro testing showed an initial drop in the interface strength, which leveled off to approximately 7.0+/-2.0 MPa.

Biomaterials, 1998 Oct, 19(20), 1855 - 60
Biodegradation of ornithine-containing polylysine hydrogels; Ohkawa K et al.; The degradation of the cross-linked cationic poly(amino acid)-glutaraldehyde (GA) hydrogels by two kinds of proteolytic enzymes, trypsin and Aspergillus Protease Type XXIII, and by seven species of soil filamentous fungi has been investigated using homo- and copolypeptides of lysine (Lys) and ornithine (Orn) . Trypsin degraded the hydrogels prepared from poly(Lys) and copoly(Lys Orn)s but not poly(Orn), while Aspergillus protease degraded all of them . Degradation time of hydrogels by the two proteases became longer with increasing Orn content in the gel . Seven species of soil filamentous fungi were cultured with hydrogels on Czapeck medium to evaluate the degree of microbial degradation of the hydrogels, and the three species of the fungi, Aspergillus oryzae, Penicillium citrinum and Curvularia sp., were grown in culture with an accompanying degradation of the gel matrix, while the other four species, Mucor sp., Rhizopus sp., Cladosporium sp., and Trichoderma sp., were not . The degree of degradation of gel matrix with growth of the three fungi became lower with increasing Orn content in the gel matrix . The results might offer some clues to the applications for the controlled biodegradation of cationic poly(amino acid) hydrogel by introduction of Orn, suggesting that unnatural amino acid resists hydrolysis by proteases or microorganisms.

Chemosphere, 1998 Dec, 37(14-15), 2859 - 71
Physical-chemical and ecotoxicological evaluation of water based drilling fluids used in Italian off-shore; Terzaghi C et al.; In order to evaluate the effects on the marine ecosystem caused by an eventual discharge into sea of water based drilling fluids, as current legislation allows, chemical and ecotoxicological analyses were performed on the most common drilling muds and products used in Italian off-shore activities . The chemical analysis on drilling fluids involved the leaching test and the measurement of total content of heavy metals, whereas biodegradation tests were performed on the products used in mud's formulations . As for ecotoxicological evaluation, two marine organisms, the crustacean Artemia salina and the diatom Phaeodactylum tricornutum, were selected to determine the LC50 and the EC50 respectively.

J Environ Sci Health B, 1998 Nov, 33(6), 705 - 21
Trichloroethylene biodegradation by phenoloxidizing cultures grown from various conditions; Lee CY et al.; The rate and extent of trichloroethylene (TCE) degradation by three cultures of phenol oxidizing bacteria grown from two chemostats and one from rotating biological contactors was investigated . Batch experiments were performed to measure the disappearance of TCE both with the resting cell alone and with the formate added . Experimental data were then compared with mathematical predictions from a model describing TCE transformation . Through nonlinear regression analysis, a best fit between the measurements and predictions was achieved when residual sum of squares reached a minimum . Based on the resultant parameters of transformation capacity and reaction rate, the suspended cells with a mean cell retention time (MCRT) of 3.8 days were the most active in degrading TCE, while the attached bacteria had the least activity . Based on the results presented herein, it is recommend that using suspended-growth reactors operated at short MCRT to produce desirable cells for cometablic transformation of TCE.

J Environ Sci Health B, 1998 Nov, 33(6), 693 - 704
Biodegradation of chlorpyrifos by either single or combined cultures of some soilborne plant pathogenic fungi; al-Mihanna AA et al.; Biodegradation of chlorpyrifos was studied in liquid culture media amended with either single or combined eight different plant pathogenic fungi isolated from the continuous cropping wheat fields . The average recovery of chlorpyrifos from the liquid media was found to be 86.1% . The detection limit of chlorpyrifos by the analytical method used was 19 ppb . Data showed that the growth of mixed fungi at concentrations up to 200 ppm of chlorpyrifos was higher than in the control treatment . Chlorpyrifos concentrations declined in the medium of combined fungi more than it did in the medium of any single fungus with increase in the incubation period . The amount of chlorpyrifos recovered was 79.8 ppm (39.9%) in the combined fungal cultures after 21 days . However, those recovered from the media of Fusarium graminearum, F . oxysporum, Rhizoctonia solani, Cladosporium cladosporiodes, Cephalosporium sp., Trichoderma viridi, Alternaria alternata, and Cladorrhinum brunnescens, ranged from 48.0 to 74.8% . The half-life value (T1/2) for chlorpyrifos was 15.8 day in the medium amended with mixed fungi . However, for the single cultures it ranged from 19.3 to 33.0 day.

Appl Microbiol Biotechnol, 1998 Oct, 50(4), 484 - 8
Methanogenic and perchloroethylene-dechlorinating activity of anaerobic granular sludge; Kennes C et al.; The biodegradation and toxicity of tetrachlorethylene (C2Cl4) and trichloroethylene (C2HCl3) were studied with different anaerobic enrichment cultures using the following electron donors: acetate, propionate, butyrate, methanol, formate and hydrogen . All of them sustained dechlorination except propionate, for which C2Cl4 biodegradation rates were not significant . The best results were obtained with butyrate . Hydrogen appeared to be a relevant electron donor for dechlorination with the present cultures . In the presence of specific inhibitors such as bromoethanesulphonate or molybdate, a slight inhibition of dechlorination was observed . According to dechlorination kinetics, Monod-type behaviour was observed up to 120 microM C2Cl4 or 200 microM C2HCl3 with Ks values around 7 microM for both compounds . Dechlorination was partially inhibited at higher concentrations . In contrast, methanogens, or at least methane production, were more sensitive to the presence of chlorinated ethylenes and inhibitions of methanogenesis was observed to different extents over all the C2Cl4/C2HCl3 concentration range tested, even at the lowest concentrations.

J Biomed Mater Res, 1998 Dec 15, 42(4), 475 - 84
Biodegradation and tumorigenicity of implanted plates made from a copolymer of epsilon-caprolactone and L-lactide in rat; Nakamura T et al.; Flat plates made from a copolymer of epsilon-caprolactone and L-lactide (P-CL-LA) {50:50 (w/w), molecular weight 1.62 x 10(5); 20 x 10 x 1 mm size} were subcutaneously implanted into 50 young, male Wistar rats (P-CL-LA group) . After 24 months the plates had become a mass of small pieces, which were concentrated in an area of 3 x 2 x 1 mm . For comparison, 50 rats were implanted with medical-grade polyethylene plates (PE group) while another set of 50 rats was subjected to the same operation but without an implant (Sham Op group) . Tumors arose in 25 rats from the P-CL-LA group: 24 were malignant mesenchymal tumors at the implant sites . In the PE group, tumors appeared in 16 rats (14 at the implant sites and two ectopically) . The average tumor latency was 578+/-84 days in the P-CL-LA group and 452+/-102 days in the PE group . There was no difference in tumor incidence between the P-CL-LA and PE groups (p < 0.05) . In the Sham Op group, two malignant tumors appeared over 2 years . Pathologically, these induced tumors arose from the inflammatory cells surrounding the degrading fragments of P-CL-LA within the tissue capsule . This indicates that relatively slowly degrading material can induce malignant tumors at a similarly high rate to nonabsorbable medical grade PE, at least in this animal model.

Biodegradation, 1998, 9(2), 151 - 6
Biodegradation of petroleum-based oil wastes through composting; Kirchmann H et al.; Composting of horse manure was used as a means of degradation of two oil wastes, oil sludge from petrol stations and petroleum residues from a refinery . Paraffin oil was chosen as a reference . Oil wastes decomposed to 78-93% during 4.5 months of composting . The degradation of the waste oils was higher than that of the reference paraffin oil and no difference was found between the two types of oil wastes concerning their decomposition . At the end of the experiment, most of the polyaromatic hydrocarbons had been degraded except pyrene, chrysene and dibenz(ah)anthracene . Gaseous losses of oil compounds through volatilisation from composts were found not to be significant.

Curr Opin Chem Biol, 1998 Oct, 2(5), 613 - 7
Microbial dehalogenases: enzymes recruited to convert xenobiotic substrates; Copley SD; Microbial dehalogenases are involved in the biodegradation of many important chlorinated pollutants . Some recent studies of haloalkane dehalogenase, dichloromethane dehalogenase, tetrachlorohydroquinone dehalogenase and perchloroethylene and trichloroethylene reductive dehalogenases have addressed the issue of recruitment and adaptation of proteins to dehalogenate novel substrates.

Biodegradation, 1998, 9(1), 39 - 45
Microbial degradation of polymeric coatings measured by electrochemical impedance spectroscopy; Gu JD et al.; This paper reports results of biodegradation studies of polyimide coatings exposed to a mixed fungal culture using electrochemical impedance spectroscopy (EIS) . The fungal consortium was originally isolated from degraded polyimides and identified species include Aspergillus versicolor, Cladosporium cladosporioides, and a Chaetomium species . Actively growing fungi on polyimides yield distinctive EIS spectra through time, indicative of failure of the polymer integrity compared to the uninoculated controls . An initial decline in coating resistance was related to the partial ingress of water molecules and ionic species into the polymeric matrices . This was followed by further degradation of the polymers by activity of the fungi . The relationship between the changes in impedance spectra and microbial degradation of the coatings was further supported by scanning electron microscopy, showing extensive colonization of the polyimide surfaces by the fungi . Our data indicate that EIS can be a sensitive and informative technique for evaluating the biosusceptibility of polymers and coatings.

Appl Microbiol Biotechnol, 1998 Sep, 50(3), 364 - 8
Biodegradation of biphenyl by the ascomycetous yeast Debaryomyces vanrijiae; Lange J et al.; Cells of the yeast strain Debaryomyces vanrijiae SBUG 770, grown with glucose, converted biphenyl to 4-hydroxybiphenyl as the major metabolite . In addition, 2-hydroxybiphenyl was formed in minor amounts . No further degradation of these substances was detected . However, these monohydroxylated derivatives were oxidised by alkane-grown cells in the presence of the co-metabolic substrate, tetradecane . Under these conditions 2-hydroxybiphenyl was oxidised to 2,5-dihydroxybiphenyl, and 4-hydroxybiphenyl was rapidly metabolised by formation of two major metabolites . One was identified as 3,4-dihydroxybiphenyl . Characterisation of the second product as 4-phenylmuconolactone points to a further metabolism of the initially formed dihydroxylated biphenyl via ortho-ring fission.

Antonie Van Leeuwenhoek, 1998 Apr, 73(3), 211 - 4
Activities of ligninolytic enzymes in some white-rot basidiomycete strains after recovering from cryopreservation in liquid nitrogen; Stoychev I et al.; Fourteen strains of white-rot basidiomycetes belonging to eight species of two genera (Inonotus and Pholiota) were tested for their ability to maintain the production of laccase, peroxidase and manganese-dependent peroxidase (enzymes involved in lignin biodegradation) after a short-time preservation in liquid nitrogen with different cryoprotectives (glycerol, dimethyl sulfoxide) . No negative effect of cryopreservation or the used cryoprotective on production of the ligninolytic enzymes was found in the fungi tested.

J Control Release, 1998 Dec 4, 56(1-3), 135 - 48
Growth factor release from amylopectin hydrogel based on copper coordination; Tabata Y et al.; This paper describes a biodegradable hydrogel matrix releasing basic fibroblast growth factor (bFGF) on the basis of protein metal coordination with the protein drug . The biodegradable hydrogel was prepared from amylopectin by its crosslinking with ethylene glycol diglycidyl ether, followed by introduction of diethylenetriaminepentaacetic acid (DTPA) residues for copper chelation . When bFGF was incorporated into the DTPA-introduced amylopectin hydrogel after chelation with Cu2+, an insignificant amount of bFGF was released from the hydrogel in buffered solution, in contrast to that without Cu2+ chelation . An increased ionic strength in the solution did not affect the bFGF release, indicating the occurrence of coordinate bonding of bFGF to the DTPA-introduced hydrogel through Cu2+ chelation . An implantation study with 125I-labeled amylopectin hydrogels demonstrated that they underwent degradation in the back subcutis of mice . Cu2+ chelation of hydrogels enabled bFGF to remain in the mouse back for a long time period, irrespective of DTPA introduction . However, DTPA residues were necessary to induce significant neovascularization by the Cu2+-chelating hydrogels incorporating bFGF . The DTPA-introduced amylopectin prevented Cu2+-induced deactivation of bFGF, again in marked contrast to DTPA-free amylopectin . It was concluded that biologically active bFGF could be incorporated to DTPA-introduced amylopectin through Cu2+ chelation in a stabilized state and was released as a result of hydrogel biodegradation, resulting in prolonged neovascularization.

Appl Environ Microbiol, 1998 Nov, 64(11), 4610 - 3
Metal toxicity reduction in naphthalene biodegradation by use of metal-chelating adsorbents
Malakul P, Srinivasan KR, Wang HY.
A model system comprising microbial degradation of naphthalene in the presence of cadmium has been developed to evaluate metal toxicity associated with polyaromatic hydrocarbon biodegradation and its reduction by the use of unmodified and surfactant-modified clays in comparison with a commercially available chelating resin (Chelex 100; Bio-Rad) . The toxicity of cadmium associated with naphthalene biodegradation was shown to be reduced significantly by using the modified-clay complex and Chelex resin, while unmodified clay has no significant impact on this reduction . The degree of metal toxicity reduction can be quantitatively related to the metal adsorption characteristics of these adsorbents, such as adsorption capacity and selectivity.

Appl Environ Microbiol, 1998 Nov, 64(11), 4180 - 4
Biodegradation of aromatic hydrocarbons in an extremely acidic environment
Stapleton RD, Savage DC, Sayler GS, Stacey G.
The potential for biodegradation of aromatic hydrocarbons was evaluated in soil samples recovered along gradients of both contaminant levels and pH values existing downstream of a long-term coal pile storage basin . pH values for areas greatly impacted by runoff from the storage basin were 2.0 . Even at such a reduced pH, the indigenous microbial community was metabolically active, showing the ability to oxidize more than 40% of the parent hydrocarbons, naphthalene and toluene, to carbon dioxide and water . Treatment of the soil samples with cycloheximide inhibited mineralization of the aromatic substrates . DNA hybridization analysis indicated that whole-community nucleic acids recovered from these samples did not hybridize with genes, such as nahA, nahG, nahH, todC1C2, and tomA, that encode common enzymes from neutrophilic bacteria . Since these data suggested that the degradation of aromatic compounds may involve a microbial consortium instead of individual acidophilic bacteria, experiments using microorganisms isolated from these samples were initiated . While no defined mixed cultures were able to evolve 14CO2 from labeled substrates in these mineralization experiments, an undefined mixed culture including a fungus, a yeast, and several bacteria successfully metabolized approximately 27% of supplied naphthalene after 1 week . This study shows that biodegradation of aromatic hydrocarbons can occur in environments with extremely low pH values.

J Control Release, 1998 Nov 13, 55(2-3), 171 - 9
Preparation and in vitro release studies of ibuprofen-loaded films and microspheres made from graft copolymers of poly(L-lactic acid) on acrylic backbones; Gallardo A et al.; The present article describes the preparation of films of various thickness and microspheres from new resorbable graft copolymers of polyacrylic (methyl methacrylate, MMA, or methyl acrylate, MA), or polyvinylic (vinyl pyrrolidone, VP) chains and poly(l-lactic acid) (PLLA) side blocks charged with 15-20% of ibuprofen (IBU) (a non-steroidic antiinflammatory agent) . In the case of MMA-LLA and MA-LLA graft copolymers the release of IBU in buffered solution is modulated by the flexibility of the copolymer chains in a first step of one to two days and in a second step by the diffusive properties of the system as well as by the biodegradation of the polymers . The VP-PLLA graft copolymers are highly hydrophilic and the release of IBU is modulated by the diffusion of the drug through the swollen system . Specific interactions between the IBU molecules and the pyrrolidone rings also participate in the kinetic behaviour of the release process.

Biomaterials, 1998 Aug, 19(16), 1473 - 8
Biphasic calcium phosphate concept applied to artificial bone, implant coating and injectable bone substitute; Daculsi G; The development of calcium phosphate ceramics and other related biomaterials for bone graft involved a better control of the process of biomaterials resorption and bone substitution . The bioactive concept was developed for biphasic calcium phosphate ceramics (BCP) . An optimum balance of the more stable phase of HA and more soluble TCP was obtained for controlling gradual dissolution in the body, seeding new bone formation as it releases calcium and phosphate ions into the biological medium . The bone/material interface and the events occurring in the development of this dynamic interface such as cellular response, biodegradation or bioresorption of the materials and their transformation to carbonate hydroxyapatite (CHA) were described . These processes were observed in both bulk samples, implant coating and injectable bone substitute (IBS).

Biochem Biophys Res Commun, 1998 Oct 20, 251(2), 399 - 402
Iron-binding catechols oxidating lignin and chlorolignin; Parra C et al.; Iron-chelating low-molecular-weight compounds or catecholate siderophores have been suggested to be involved in wood biodegradation . To help in understanding the mechanism involved in the enzyme-like activity of catecholate siderophores, the oxidative properties of 2,3-dihydroxybenzoic acid (DHBA) and 3, 4-dihydroxyphenylacetic acid (DHPAA) chelated with iron were studied . The pH and catechol/Fe(III) ratios were optimized for o-dianisidine oxidation, obtaining a maximum at pH 7.0, in the absence of buffer, and a catechol/Fe(III) ratio of 1:2 to DHBA and 1:1 to DHPAA was found . Under these conditions, the catechols were able to reduce Fe(III) to Fe(II) acting like siderophore models . The Fe(III) complex of DHBA and of DHPAA degraded dioxane-lignin in 60% after 2 h and 85% after 24 h, respectively . DHBA/Fe(III) oxidized the bleaching effluent (E1) in 80% in 5 min under the studied conditions .

J Biomed Mater Res, 1998 Dec 5, 42(3), 357 - 67
Comparative study of tissue reactions to calcium phosphate ceramics among cancellous, cortical, and medullar bone sites in rabbits; Lu JX et al.; In order to understand the influence of the implantation site on bone biomaterial evaluation, we implanted cylinders of HA and beta-TCP ceramics in the femoral diaphysis and condyle of rabbits . After 3, 8, 12, and 24 weeks of implantation, histological investigation and histomorphometry were performed on undecalcified samples . Our results show that spontaneous bone healing in the empty cavities is significantly different (p < 0.05) between cortical (SBH > 80%) and cancellous bone sites (SBH < 31%) and that no new bone is formed in marrow tissue . For both porous ceramics, the highest osteogenesis was obtained in the cortical site . Osteogenesis was intermediate in the cancellous site and weak in the medullar site . The material biodegradation was the strongest in the medullar site and higher in the cancellous site than in the cortical site . Both activities were better in the beta-TCP than in the HA (p > 0.05) . The marrow tissue presents a foreign-body reaction more reliable, sensitive, and durable than other bone tissues . Therefore, the cancellous bone site is a good site for evaluation of the biofunctionality of biomaterials because of the equilibrium of the osteogenesis and the biodegradation activities, but marrow tissue seems to be better for testing material biocompatibility in vivo.

Can J Microbiol, 1998 Jul, 44(7), 605 - 22
A review of the occurrence, toxicity, and biodegradation of condensed thiophenes found in petroleum; Kropp KG et al.; Condensed thiophenes comprise a significant portion of the organosulfur compounds in petroleum and in other products from fossil fuels . Dibenzothiophene (DBT) has served as a model compound in biodegradation studies for over two decades . However, until quite recently, few other organosulfur compounds were studied, and their fates in petroleum-contaminated environments are largely unknown . This paper presents a review of the types of organosulfur compounds found in petroleum and summarizes the scant literature on toxicity studies with condensed thiophenes . Reports on the biodegradation of benzothiophene, alkylbenzothiophenes, DBT, alkylDBTs, and naphthothiophenes are reviewed with a focus on the identification of metabolites detected in laboratory cultures . In addition, recent reports on quantitative studies with DBT and naphtho{2,1-b}thiophene indicate the existence of polar sulfur-containing metabolites that have escaped detection and identification.

Arch Environ Contam Toxicol, 1998 Nov, 35(4), 580 - 7
Environmental effects of sodium Acetate/Formate deicer, ice sheartrade mark
Bang SS, Johnston D.
The environmental impacts of Ice Sheartrade mark, an alternative highway deicer, have been evaluated using standard laboratory tests; biochemical oxygen demand (BOD) tests, chemical oxygen demand (COD) tests, acute rainbow trout bioassays, and phytotoxicity tests were used . Ice Shear consists of equimolar sodium acetate and sodium formate . The organic matter of the deicer can be readily degraded microbiologically in the natural environment with a slow rate of degradation at lower temperatures but an increased rate at higher temperatures . At elevated temperatures, highway runoffs of the deicer may reduce the level of dissolved oxygen in the receiving waters to cause an adverse impact . However, the apparent activation energy calculated for the BOD rate of Ice Shear is low (8.78 kcal mole-1), indicating that the temperature variation may not significantly influence the biodegradation of the deicer compound . Ice Shear appears relatively harmless to aquatic animals, showing a high 96-h LC50 value (16.1 g/L) derived for rainbow trout (Oncorhynchus mykiss) . Ice Shear causes minimal toxicity to representative roadside vegetation; herbaceous (e.g., sunflowers, beans, and lettuce) and woody (e.g., pine seedlings) plants . Rather, the deicer at low concentrations (less than 2 g/kg soil) seems to work as a fertilizer, promoting the yield of biomass . The test results indicate that Ice Shear poses minimal environmental disturbance in both aquatic and terrestrial ecosystems.

J Biomater Appl, 1998 Oct, 13(2), 158 - 65
Polyethylene glycol (PEG) modified bovine pericardium as a biomaterial: a comparative study on immunogenicity; Aravind S et al.; Bioprosthetic heart valves made from glutaraldehyde (GA)-fixed porcine aortic valves or bovine pericardium (BP) are having some advantages over mechanical valves . However, their durability is low due to the calcification and immunological rejection . Study on immunogenicity is an important part in understanding the biocompatibility of materials . Polyethylene glycol (PEG) on pericardium can control biodegradation and calcification . Also, PEG exhibits low immunogenicity . We have studied the complement activation potential and the contribution of complement factors (biologic factors) on the calcification of PEG grafted pericardium samples and compared with standard (control) glutaraldehyde-treated pericardium samples . PEG-grafted BP activated using GA and carbodiimide (EDC) could be selected for further studies since complement activation and calcification observed on these samples has been relatively low.

J Biomed Mater Res, 1998 Nov, 42(2), 303 - 11
Biodegradation and biocompatibility of a guided tissue regeneration barrier membrane formed from a liquid polymer material; Coonts BA et al.; Biodegradable barrier films were made by coagulating a solution of poly(DL-lactide) in N-methyl-2-pyrrolidone on porous polyethylene pads wetted with saline solution . The semisolid films were cut into 10 x 10 mm barriers and implanted subcutaneously in rabbits . At monthly intervals, the polymer implant sites were compared histologically to those implanted with USP negative control plastic . The polymer films were retrieved from the surrounding tissue, dried, weighed, and the changes in molecular weight determined using gel permeation chromatography . The molecular weight of the polymer decreased at a relatively constant rate over 5 months; however, no significant mass loss occurred until 5 months postimplantation . Also, no distinct histological differences were noted between the polymer barrier and the control plastic sites until 6 months when histiocytes and multinucleated giant cells showed a modest increase around fragmented polymer films . Similar barrier films also were fitted over naturally occurring buccal dehiscence defects in beagle dogs and the tissue sites compared histologically at 6 months to sham-operated control sites . New bone and dense connective tissues closely approximated segments of the remaining polymer and demonstrated the biocompatibility of the biodegradable films . Histomorphometric analyses of treated sites compared to sham controls showed that the polymer barrier is effective in promoting bone and cementum regeneration in periodontal defects in dogs.

J Biomed Mater Res, 1998 Nov, 42(2), 199 - 212
Decreased consumption of Ca and P during in vitro biomineralization and biologically induced deposition of Ni and Cr in presence of stainless steel corrosion products; Morais S et al.; The purpose of this study was to investigate the effects of 316L stainless steel (SS) corrosion products on the in vitro biomineralization process, because tissue necrosis, bone loss, impaired bone mineralization, and loosening of orthopedic implants are associated with ions and debris resulting from biodegradation . Rat bone marrow cells were cultured in experimental conditions that favored the proliferation and differentiation of osteoblastic cells and were exposed to SS corrosion products obtained by electrochemical means for periods ranging from 1 to 21 days . Quantification of total and ionized Ca and P, as well as Fe, Cr, and Ni, ions in the culture media of control and metal added cultures during the incubation period was performed to study the influence of corrosion products on the Ca and P consumption that occurs during the mineralization process . Control cultures and metal effects on cultures were evaluated concerning DNA content, enzymatic reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and alkaline phosphatase (ALP) activity . Histochemical detection of ALP, Ca, and phosphate deposition, and examination of the cultures by scanning and transmission electron microscopy (SEM and TEM) were also performed . The presence of SS corrosion products resulted in impairment of the normal behavior of rat bone marrow cultures . Levels of Cr and Ni in the medium of cultures exposed to 316L SS corrosion products decreased throughout the incubation period, suggesting a regular deposition of these species; these results were supported by TEM observation of the cultures . Cultures exposed to the corrosion products presented lower DNA content, MTT reduction, and ALP activity and failed to form mineralized areas . These cultures showed negative staining on histochemical reactions for the identification of calcium and phosphate deposition and SEM and TEM examination did not show mineral globular structures or mineralization foci, respectively, which is characteristic of cultures grown in control conditions . These results suggest that metal ions associated with 316L SS are toxic to osteogenic cells, affecting their proliferation and differentiation.

Life Sci, 1998, 63(15), 1377 - 85
Slide-binding characterization and autoradiographic localization of delta opioid receptors in rat and mouse brains with the tetrapeptide antagonist {3H}TIPP; Bakota L et al.; Slide-binding and autoradiographic studies were performed on cryostat sections from brains of adult Sprague-Dawley rats and BALB C mice to describe the binding characteristics of the tetrapeptide {3H}TIPP, an antagonist with high specificity and affinity for the delta opioid receptors . Steady-state binding of {3H}TIPP to cryostat sections of brain paste was reached in 120-180 min of incubation . Specific {3H}TIPP binding resulted in maximal numbers of binding sites (Bmax) of 15.59 and 23.91 fmol/mg protein, and dissociation constants (Kd) of 0.46 and 0.85 nM for rat and mouse brain paste sections, respectively . TIPP displayed the highest affinity for delta opioid receptors in inhibiting specific {3H}TIPP binding, with IC50 values of 0.82 nM and 0.14 nM in rat and mouse brain sections, respectively . While DPDPE was also effective in displacing the specific binding of {3H}TIPP (IC50 = 3.18 +/- 0.53 nM and 0.63 +/- 0.42 nM in rat and mouse brain paste sections, respectively), other subclass-selective or nonopioid ligands were much less effective, or ineffective . Autoradiographic localization of {3H}TIPP binding revealed the characteristic distribution of delta opioid receptors in both species . In consequence of its antagonistic nature, and of its unnatural amino acid residue, which makes this ligand more resistant to biodegradation, {3H}TIPP is a superior ligand for evaluation of the binding characteristics and autoradiogaphic distribution of the delta opioid receptors.

Res Microbiol, 1998 Jun, 149(6), 399 - 406
Biodegradation of phenol and p-cresol by the hyphomycete Scedosporium apiospermum; Claussen M et al.; A hyphomycete with the ability to utilize phenol and p-cresol as carbon and energy source was isolated from soil and subsequently identified as Scedesporium apiospermum . The identification of degradation metabolites and the detection of the corresponding catabolic enzymes in crude extracts enabled us to propose different pathways for the degradation of both phenol and p-cresol in this organism . Generally, the catabolism proceeded via three different dihydroxylated intermediates (catechol, hydroxyhydroquinone and protocatechuate) which were intradiolically cleaved by the corresponding inducible dioxygenases and further catabolized via the 3-oxoadipate pathway.

Acta Crystallogr D Biol Crystallogr, 1998 May 1, 54 ( Pt 3), 430 - 2
Crystallization and preliminary X-ray diffraction studies of the catalytic core of acetyl xylan esterase from Trichoderma reesei; Hakulinen N et al.; Acetyl xylan esterase is involved in the biodegradation of hemicellulose . It cleaves O-acetyl groups from xylan, which is the most abundant hemicellulose in nature . The catalytic core of acetyl xylan esterase from T . reesei has been crystallized and X-ray diffraction data at 2.3 A collected . The crystal belongs to the triclinic space group P1 with unit-cell parameters a = 50.3, b = 62 . 1, c = 40.0 A, alpha = 110.1, beta = 113.6 and gamma = 97.9 degrees . The asymmetric unit contains two molecules.

Biomaterials, 1998 Aug, 19(15), 1371 - 85
In vivo UHMWPE biodegradation of retrieved prosthesis; Costa L et al.; Sixty-two ultra high molecular weight polyethylene prosthetic components (PEs) (31 tibial plateaux and 31 cups), sterilised by gamma rays or ethylene oxide (EtO), were retrieved after 1-12 years depending on different medical reasons and were studied by FTIR spectroscopy with derivatisation of oxidised species . Esters, acids and hydroperoxides were found under the surface of the EtO sterilised PEs up to 2 mm depth . The behaviour of gamma ray sterilised PEs is more complex due to the oxidation following the sterilisation process . Ester and acid formation might arise from the diffusion of components of synovial liquid or from the oxidation process, whereas hydroperoxide formation is thought to be due to the oxidation . Abrasion and delamination process is discussed considering the topological distribution of degradation products.

Rev Environ Contam Toxicol, 1998, 158, 53 - 128
Environmental chemistry and toxicology of polychlorinated n-alkanes; Tomy GT et al.; Polychlorinated-n-alkanes (PCAs) or chlorinated paraffins consist of C10 to C30 n-alkanes with chlorine content from 30% to 70% by mass . PCAs are used as high-temperature lubricants, plasticizers, flame retardants, and additives in adhesives, paints, rubber, and sealants . This review presents the existing data on the environmental chemistry and toxicology of PCAs and a preliminary exposure and risk assessment . There is limited information on the levels, fate, or biological effects of PCAs in the environment . This results both from the difficulty associated with quantifying PCAs, because of the complexity inherent to commercial formulations, and from the limited knowledge of their physicochemical properties and biodegradation rates . There are indications that PCAs are widespread environmental contaminants at ng/L levels in surface waters and ng/g (wet wt) levels in biota . However, environmental measurements of PCAs are very limited in the U.S . and Canada, and are only slightly more detailed in western Europe . Assuming that reported water concentrations are mainly caused by the short chain (C10-C13) compounds, aquatic organisms may be at risk from exposure to PCAs . Fugacity level II modeling for two representative PCAs, using the best available physicochemical property data and estimated degradation rates, suggested that C16C24Cl10 would achieve higher concentrations in biota, sediment, and soil than C12H20Cl6 because of slower degradation rates and lower water solubility . Environmental residence time of C16H24Cl10 is estimated to be 520 d compared to 210 d for C12H20Cl6 . Future studies will require better analytical methods and reference materials certified for PCA content . Additional data are needed to evaluate exposure of biota to PCAs in the environment, particularly in light of their continued production and usage around the globe.

Can J Microbiol, 1998 May, 44(5), 456 - 64
Microbial utilization of the neurotoxin domoic acid: blue mussels (Mytilus edulis) and soft shell clams (Mya arenaria) as sources of the microorganisms; Stewart JE et al.; The neurotoxin domoic acid is produced in quantity by the diatom Pseudo-nitzschia multiseries and is released to the environment directly and indirectly via food chains . Presumably there is a mechanism for the biodegradation and disposal of domoic acid and as bacteria are logical candidates for such an activity, a search for bacteria competent to carry out biodegradation of domoic acid was initiated . Extensive trials with a wide variety of bacteria isolated mainly from muds and waters taken from the marine environment showed that the ability to grow on or degrade domoic acid was rare; in fact, domoic acid was inhibitory to resting cells or growing cultures of most of these bacteria . In contrast, using enrichment techniques, it was possible to isolate from molluscan species that eliminate domoic acid readily, i.e., blue mussels (Mytilus edulis) and soft-shell clams (Mya arenaria), bacteria that exhibited growth with and biodegradation of domoic acid when supplemented with low concentrations of growth factors . The species that retain domoic acid for lengthy periods, such as sea scallops (Placopecten magellanicus) and red mussels (Modiolus modiolus), only occasionally yielded bacteria with this capability . The differences may be a result of the mechanisms used by the different shellfish in dealing with domoic acid, i.e., freely available in the blue mussels and soft-shell clams but likely sequestered in the digestive glands of sea scallops and red mussels and thus, largely unavailable for bacterial utilization . The results show that Mytilus edulis and Mya arenaria, almost uniquely, are prime and reliable sources of domoic acid utilizing bacteria . These findings suggest a strong possibility that autochthonous bacteria may be significant factors in the elimination of the neurotoxin in these two species of shellfish.

J Control Release, 1998 Apr 30, 53(1-3), 93 - 103
Controlled chemical modification of hyaluronic acid: synthesis, applications, and biodegradation of hydrazide derivatives; Prestwich GD et al.; Controlled modification of the carboxylic acid moieties of hyaluronic acid with mono- and polyfunctional hydrazides leads to biochemical probes, biopolymers with altered physical and chemical properties, tethered drugs for controlled release, and crosslinked hydrogels as biocompatible scaffoldings for tissue engineering . Methods for polyhydrazide synthesis, for prodrug preparation, for hydrogel crosslinking, and for monitoring biodegradation are described.

Crit Rev Ther Drug Carrier Syst, 1998, 15(4), 381 - 420
Bioerodible polymers for ocular drug delivery; Deshpande AA et al.; Development of ophthalmic drug-delivery systems has always been challenging . The commonly used route for drug delivery to the anterior segment of the eye has been the conjunctival cul-de-sac . Because of drawbacks associated with this route, new approaches have been investigated for delivery of drugs to the eye by means of polymeric delivery systems . Development of controlled drug-release devices has been a major step forward in this respect . Bioerodible polymers have been at the forefront of such systems . They are very important because they eliminate the need for removing the implant after complete drug release . Bioerodible polymers have been divided into three classes based on their mechanism of hydrolysis: Type I--hydrolysis of crosslinked hydrogels; Type II--solubilization by ionization or hydrolysis of linear polymers; and Type III--biodegradation by backbone cleavage . Polymers from all three classes are discussed in detail in this review.

Chemosphere, 1998 Sep, 37(7), 1317 - 33
The ecotoxicity and the biodegradability of lactic acid, alkyl lactate esters and lactate salts; Bowmer CT et al.; The ecotoxicity of lactic acid, its alkyl esters and selected metal salts was studied experimentally with the micro alga Selenastrum capricornutum, the crustacean Daphnia magna and the fish species Brachydanio rerio and Pimephales promelas . In addition, the biodegradation of lactate esters was also studied . The aim of the study was to provide predicted environmental data for additional alkyl homologues and metal salts . The ecotoxicity data are evaluated by means of Structure Activity Relations (SAR), using literature data on a non-polar narcotic mechanism of toxicity as a baseline for comparison . Lactate salts were evaluated by comparison to the toxicity of the metal ion . For the fish and D . magna, it was evident that methyl, ethyl, propyl and to a lesser extent butyl lactate were slightly more toxic in comparison to baseline non-polar narcotic toxicity data . The toxicity tests carried out with lactate-salts demonstrated clearly that the toxicity in standard tests is only determined by the associated cation and not by the lactate part . Lactic acid and its alkyl esters were degraded for more than 60% in the ready biodegradability tests and from the data presented, it is evident that the majority of alkyl lactates are readily biodegradable . The results presented in this study indicate that alkyl lactate esters show some differences in their ecotoxicity when compared to non polar narcotic compounds in but that these differences are generally small . When aquatic toxicity is considered together with their rapid tendency to biodegrade, it is concluded that lactate esters show generally favourable environmental characteristics.

Bioorg Med Chem, 1998 Jul, 6(7), 967 - 73
Structural modifications induced during biodegradation of wheat lignin by Lentinula edodes; Crestini C et al.; The structural modifications occurring during wheat straw lignin biodegradation were evaluated by the concerted use of 31P-, 1H- and 2D homo- and heteronuclear NMR spectroscopies . Straw lignin was found to be oxidatively degraded via stereoselective side-chain oxidation as evidenced by a lower erythro/threo ratio . Significantly lower amounts of phenolic hydroxy and methoxy groups in the decayed lignin may be indicative that its structure after the fungal treatment contained a lower amount of aromatic units . In addition an increase in carboxylic acids content, that cannot be explained only on the basis of side-chain oxidation reactions, was also apparent . This evidence, coupled with pertinent data collected during this effort, suggests the occurrence of aromatic ring cleavage reactions . In fact the oxidative degradation of lignin model compounds by fungi has been reported to occur via the 3-oxoadipate pathway which is known to cause aromatic ring cleavage with the formation of aliphatic chains . The presence of aliphatic moieties in the decayed lignin was confirmed by detailed 1H- and 2D NMR spectroscopic analyses.

J Biotechnol, 1998 Jul 16, 62(3), 221 - 30
Copper-dependent depolymerization of lignin in the presence of fungal metabolite, pyridine; Watanabe T et al.; Thus far, it has not been recognized that copper complexes are able to depolymerize lignin under physiological conditions of white rot decay . However, we have found that both phenolic and non-phenolic synthetic lignins were intensively depolymerized by Cu(II) and lipid hydroperoxide model compounds in the presence of a metabolite of ligninolytic fungi, pyridine at room temperature in aqueous media . Treatment of 14C-labeled oxygen-prebleached kraft pulp (OKP) by the copper-dependent reaction evidenced effectiveness of this reaction for the delignification of kraft pulps . In contrast to the organic peroxide system, Cu(II)/pyr/H2O2 system was much less effective for the lignin depolymerization . However, treatment of unbleached kraft pulp (UKP) by Cu(II)/H2O2 and Cu(II)/pyr/H2O2 systems demonstrated that the damage of cellulose was suppressed by the coordination of pyridine although high brightness gain was obtained independently of the presence of the coordinator . Spin trapping experiments demonstrated that not hydroxyl radical but superoxide anion is involved in the Cu(II)/pyr/H2O2 system . This finding not only introduces a new concept of non-enzymatic lignin biodegradation by wood-degrading fungi but also presents a new strategy for decomposing lignin and lignin-related compounds by copper complexes and peroxide-producing system.

Proc Natl Acad Sci U S A, 1998 Sep 1, 95(18), 10373 - 7
Rapid polyether cleavage via extracellular one-electron oxidation by a brown-rot basidiomycete; Kerem Z et al.; Fungi that cause brown rot of wood are essential biomass recyclers and also the principal agents of decay in wooden structures, but the extracellular mechanisms by which they degrade lignocellulose remain unknown . To test the hypothesis that brown-rot fungi use extracellular free radical oxidants as biodegradative tools, Gloeophyllum trabeum was examined for its ability to depolymerize an environmentally recalcitrant polyether, poly(ethylene oxide) (PEO), that cannot penetrate cell membranes . Analyses of degraded PEOs by gel permeation chromatography showed that the fungus cleaved PEO rapidly by an endo route . 13C NMR analyses of unlabeled and perdeuterated PEOs recovered from G . trabeum cultures showed that a major route for depolymerization was oxidative C---C bond cleavage, a reaction diagnostic for hydrogen abstraction from a PEO methylene group by a radical oxidant . Fenton reagent (Fe(II)/H2O2) oxidized PEO by the same route in vitro and therefore might account for PEO biodegradation if it is produced by the fungus, but the data do not rule out involvement of less reactive radicals . The reactivity and extrahyphal location of this PEO-degrading system suggest that its natural function is to participate in the brown rot of wood and that it may enable brown-rot fungi to degrade recalcitrant organopollutants.

J Bacteriol, 1998 Sep, 180(17), 4591 - 5
Purification, characterization, and sequence analysis of 2-aminomuconic 6-semialdehyde dehydrogenase from Pseudomonas pseudoalcaligenes JS45; He Z et al.; 2-Aminonumconic 6-semialdehyde is an unstable intermediate in the biodegradation of nitrobenzene and 2-aminophenol by Pseudomonas pseudoalcaligenes JS45 . Previous work has shown that enzymes in cell extracts convert 2-aminophenol to 2-aminomuconate in the presence of NAD+ . In the present work, 2-aminomuconic semialdehyde dehydrogenase was purified and characterized . The purified enzyme migrates as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular mass of 57 kDa . The molecular mass of the native enzyme was estimated to be 160 kDa by gel filtration chromatography . The optimal pH for the enzyme activity was 7.3 . The enzyme is able to oxidize several aldehyde analogs, including 2-hydroxymuconic semialdehyde, hexaldehyde, and benzaldehyde . The gene encoding 2-aminomuconic semialdehyde dehydrogenase was identified by matching the deduced N-terminal amino acid sequence of the gene with the first 21 amino acids of the purified protein . Multiple sequence alignment of various semialdehyde dehydrogenase protein sequences indicates that 2-aminomuconic 6-semialdehyde dehydrogenase has a high degree of identity with 2-hydroxymuconic 6-semialdehyde dehydrogenases.

Appl Microbiol Biotechnol, 1998 Jul, 50(1), 135 - 41
Anaerobic biodegradation of pentachlorophenol in a contaminated soil inoculated with a methanogenic consortium or with Desulfitobacterium frappieri strain PCP-1; Beaudet R et al.; Anaerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil from a wood-treating industrial site was studied in soil slurry microcosms inoculated with a PCP-degrading methanogenic consortium . When the microcosms containing 10%-40% (w/v) soil were inoculated with the consortium, more than 90% of the PCP was removed in less than 30 days at 29 degrees C . Less-chlorinated phenols, mainly 3-chlorophenol were slowly degraded and accumulated in the cultures . Addition of glucose and sodium formate to the microcosms was not necessary, suggesting that the organic compounds in the soil can sustain the dechlorinating activity . Inoculation of Desulfitobacterium frappieri strain PCP-1 along with a 3-chlorophenol-degrading consortium in the microcosms also resulted in the rapid dechlorination of PCP and the slow degradation of 3-chlorophenol . Competitive polymerase chain reaction experiments showed that PCP-1 was present at the same level throughout the 21-day biotreatment . D . frappieri, strain PCP-1, inoculated into the soil microcosms, was able to remove PCP from soil containing up to 200 mg PCP/kg soil . However, reinoculation of the strain was necessary to achieve more than 95% PCP removal with a concentration of 300 mg and 500 mg PCP/kg soil . These results demonstrate that D . frappieri strain PCP-1 can be used effectively to dechlorinate PCP to 3-chlorophenol in contaminated soils.

Environ Health Perspect, 1998 Aug, 106 Suppl 4, 1069 - 74
By-products of a former phenol manufacturing site in a small lake adjacent to a Superfund site in the Aberjona watershed; Wick LY et al.; Benzene, diphenyl sulfone (DPS), para-hydroxybiphenyl (PPP), ortho-hydroxybiphenyl (OPP), higher hydroxybiphenyls, and alkylated benzenes were found in a small lake receiving contaminated groundwater discharge from the Industri-Plex Superfund site (Woburn, MA) in the Aberjona watershed in eastern Massachusetts . All of these chemicals may derive from the former phenol manufacturing activities present at the Industri-Plex site during World War I . Concentrations up to 1660 microgram/l benzene, 450 micro/l DPS, 230 microgram/l PPP, and 100 microgram/l OPP were detected in the hypolimnion . Epilimnetic concentrations of the chemicals were significantly lower (normally < 5 microgram/l) . DPS showed a distinct seasonal behavior: It was readily biodegradable during warm periods . No biodegradation was observed in the winter, leaving export to the Aberjona River as the major removal mechanism . Although benzene is known to be toxic and a human carcinogen, our results indicate that DPS, OPP, and PPP are not mutagenic in tests using human MCL-5 and h1A1v2 cell lines.

J Biomed Mater Res, 1998 Sep 15, 41(4), 584 - 92
Assessment of an experimental bone wax polymer plus TGF-beta 1 implanted into calvarial defects; Schmitt JM et al.; The study reported describes an experimental biodegradable polymer ceramic composite with wax-like handling properties that was combined with 2.0 micrograms of recombinant human transforming growth factor beta (rhTGF-beta(1)) . The polymer/rhTGF-beta(1) combination was introduced into standard-sized calvarial defects in rabbits to evaluate biodegradability, biocompatibility, hemostasis control, and bone promotion . The experimental wound model was a standard-size circular calvarial defect 8 mm in diameter . The experimental design included 24 skeletally mature New Zealand white rabbits divided evenly between two time periods (6 and 12 weeks) and among three experimental treatments (untreated defects and defects treated with polymer with or without rhTGF-beta(1)) . Evaluations consisted of clinical examinations, standarized radiography, radiomorphometry, as well as histology and histomorphometry . Data were analyzed by an Analysis of Variance (ANOVA) and Fisher's Protected Least Significant Difference test at each time period (level of significance p < or = 0.05) . Radiomorphometry data indicated that standard-sized defects treated with the wax-like polymer alone and the polymer plus 2.0 micrograms of TGF-beta(1) were significantly more radiopaque than control sites at both 6 and 12 weeks . Histomorphometric data revealed the amount of new bone was significantly greater at 6 weeks in the polymer plus 2.0 micrograms of TGF-beta(1) and in the control group than in the polymer alone . Moreover, at 12 weeks, there was significantly more new bone in the control than in either the polymer alone or the polymer plus 2.0 micrograms of TGF-beta(1) . We speculate the incomplete biodegradation of the polymer ceramic composite contributed to the radiopacity and may have retarded osseous regeneration . It is important that the bone wax-like polymer material was biocompatible and acted as a hemostatic agent.

Toxicon, 1998 Jul, 36(7), 953 - 62
The toxicology of microcystins; Dawson RM; Microcystins are a family of more than 50 structurally similar hepatotoxins produced by species of freshwater cyanobacteria, primarily Microcystis aeruginosa . They are monocyclic heptapeptides, characterised by some invariant amino acids, including one of unusual structure which is essential for expression of toxicity . Microcystins are chemically stable, but suffer biodegradation in reservoir waters . The most common member of the family, microcystin-LR (L and R identifying the 2 variable amino acids, in this case leucine and arginine respectively) has an LD50 in mice and rats of 36-122 microg/kg by various routes, including aerosol inhalation . Although human illnesses attributed to microcystins include gastroenteritis and allergic/irritation reactions, the primary target of the toxin is the liver, where disruption of the cytoskeleton, consequent on inhibition of protein phosphatases 1 and 2A, causes massive hepatic haemorrhage . Microcystins are tight-binding inhibitors of these protein phosphatases, with inhibition constants in the nanomolar range or lower . Uptake of microcystins into the liver occurs via a carrier-mediated transport system, and several inhibitors of uptake can antagonise the toxic effects of microcystins . The most effective of these is the antibiotic rifampin (a drug approved for clinical use), which protects mice and rats against microcystin-induced lethality when given prophylactically and, in some cases, therapeutically.

Braz J Med Biol Res, 1997 Dec, 30(12), 1407 - 14
Genetic engineering of baker's and wine yeasts using formaldehyde hyperresistance-mediating plasmids; Schmidt M et al.; Yeast multi-copy vectors carrying the formaldehyde-resistance marker gene SFA have proved to be a valuable tool for research on industrially used strains of Saccharomyces cerevisiae . The genetics of these strains is often poorly understood, and for various reasons it is not possible to simply subject these strains to protocols of genetic engineering that have been established for laboratory strains of S . cerevisiae . We tested our vectors and protocols using 10 randomly picked baker's and wine yeasts all of which could be transformed by a simple protocol with vectors conferring hyperresistance to formaldehyde . The application of formaldehyde as a selecting agent also offers the advantage of its biodegradation to CO2 during fermentation, i.e., the selecting agent will be consumed and therefore its removal during down-stream processing is not necessary . Thus, this vector provides an expression system which is simple to apply and inexpensive to use.

J Bacteriol, 1998 Aug, 180(15), 3823 - 7
Purification and characterization of EDTA monooxygenase from the EDTA-degrading bacterium BNC1; Payne JW et al.; The synthetic chelating agent EDTA can mobilize radionuclides and heavy metals in the environment . Biodegradation of EDTA should reduce this mobilization . Although several bacteria have been reported to mineralize EDTA, little is known about the biochemistry of EDTA degradation . Understanding the biochemistry will facilitate the removal of EDTA from the environment . EDTA-degrading activities were detected in cell extracts of bacterium BNC1 when flavin mononucleotide (FMN), NADH, and O2 were present . The degradative enzyme system was separated into two different enzymes, EDTA monooxygenase and an FMN reductase . EDTA monooxygenase oxidized EDTA to glyoxylate and ethylenediaminetriacetate (ED3A), with the coconsumption of FMNH2 and O2 . The FMN reductase provided EDTA monooxygenase with FMNH2 by reducing FMN with NADH . The FMN reductase was successfully substituted in the assay mixture by other FMN reductases . EDTA monooxygenase was purified to greater than 95% homogeneity and had a single polypeptide with a molecular weight of 45,000 . The enzyme oxidized both EDTA complexed with various metal ions and uncomplexed EDTA . The optimal conditions for activity were pH 7.8 and 35 degreesC . Kms were 34.1 microM for uncomplexed EDTA and 8.5 microM for MgEDTA2-; this difference in Km indicates that the enzyme has greater affinity for MgEDTA2- . The enzyme also catalyzed the release of glyoxylate from nitrilotriacetate and diethylenetriaminepentaacetate . EDTA monooxygenase belongs to a small group of FMNH2-utilizing monooxygenases that attack carbon-nitrogen, carbon-sulfur, and carbon-carbon double bonds.

J Biotechnol, 1998 May 13, 61(3), 209 - 18
The biodegradation of recalcitrant effluents from an olive mill by a white-rot fungus; D'Annibale A et al.; Biodegradation of olive-mill wastewater (OMW) was performed by the polyurethane-immobilized mycelium of Lentinula edodes . Throughout three consecutive treatment cycles of the effluent significant abatements of its polluting characteristics were observed . In fact, its contents in total organic carbon, total phenols, total ortho-diphenol were dramatically reduced . In addition, a significant effluent decolorization was evident.

Appl Microbiol Biotechnol, 1998 Jun, 49(6), 663 - 8
Simulation of in situ subsurface biodegradation of polychlorophenols in air-lift percolators
Langwaldt JH, Mannisto MK, Wichmann R, Puhakka JA.
Air-lift percolator experiments simulated in situ subsurface degradation of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol, in mixtures and individually, by indigenous microorganisms from a chlorophenol-contaminated aquifer . Inoculation with a chlorophenol(CP)-degrading gram-positive isolate from the CP-contaminated groundwater did not significantly increase CP degradation rates . Feed concentrations of up to 55 mg CP l-1 were degraded . Stable CP degradation was maintained for over 6 months . CP degradation rates up to 54.3 mg l-1 day-1 and effluent concentrations below 40 micrograms CP l-1 were achieved . CP were mineralized as shown by CP reduction, dissolved organic carbon removal and release of inorganic chloride.

J Bacteriol, 1998 Aug, 180(15), 3954 - 66
Genetic analysis of dioxin dioxygenase of Sphingomonas sp . Strain RW1: catabolic genes dispersed on the genome; Armengaud J et al.; The dioxin dioxygenase of Sphingomonas sp . strain RW1 activates dibenzo-p-dioxin and dibenzofuran for further metabolism by introducing two atoms of oxygen at a pair of vicinal carbon atoms, one of which is involved in one of the bridges between the two aromatic rings, i.e., an angular dioxygenation . The dxnA1 and dxnA2 cistrons encoding this dioxygenase have been cloned and shown to be located just upstream of a hydrolase gene which specifies an enzyme involved in the subsequent step of the dibenzofuran biodegradative pathway . Genes encoding the electron supply system of the dioxygenase are not clustered with the dioxygenase gene but rather are located on two other distinct and separate genome segments . Moreover, whereas expression of dxnA1A2 is modulated according to the available carbon source, expression of the dbfB gene encoding the ring cleavage enzyme of the dibenzofuran pathway, which is located in the neighborhood of dxnA1A2 but oriented in the opposite direction, is constitutive . The scattering of genes for the component proteins of dioxin dioxygenase system around the genome of Sphingomonas sp . strain RW1, and the differential expression of dioxin pathway genes, is unusual and contrasts with the typical genetic organization of catabolic pathways where component cistrons tend to be clustered in multicistronic transcriptional units . The sequences of the alpha and beta subunits of the dioxin dioxygenase exhibit only weak similarity to other three component dioxygenases, but some motifs such as the Fe(II) binding site and the {2Fe-2S} cluster ligands are conserved . Dioxin dioxygenase activity in Escherichia coli cells containing the cloned dxnA1A2 gene was achieved only through coexpression of the cognate electron supply system from RW1 . Under these conditions, exclusively angular dioxygenation of dibenzofuran and dibenzo-p-dioxin was obtained . The dioxin dioxygenase was not active in E . coli cells coexpressing a class IIB electron supply system . In the course of the isolation of the dxnA1 and dxnA2 cistrons, a number of other catabolic genes dispersed over different genome segments were identified, which may indicate greater catabolic potential than was previously suspected . This finding is consistent with the catabolic versatility of members of the genus Sphingomonas, which is becoming increasingly evident, and may indicate a less well evolved and regulated but more dynamic genetic organization in this organism than is the case for better-studied pathways in organisms such as Pseudomonas species.

Extremophiles, 1997 May, 1(2), 100 - 5
Biodegradation of indole at high concentration by persolvent fermentation with Pseudomonas sp . ST-200; Doukyu N et al.; Pseudomonas sp . strain ST-200 grew on indole as a sole carbon source . The minimal inhibitory concentration of indole was 0.3 mg/ml for ST-200 . However, ST-200 grew in a persolvent fermentation system containing a large amount of indole (a medium containing 20% by vol . diphenylmethane and 4 mg/ml indole), because most of the indole was partitioned in the organic solvent layer . When the organism was grown in the medium containing indole at 1 mg/ml in the presence of diphenylmethane, more than 98% of the indole was consumed after 48h . Isatic acid (0.4 mg/ml) and isatin (0.03 mg/ml) were produced as the metabolites in the aqueous medium layer.

Biomaterials, 1998 Jan-Feb, 19(1-3), 61 - 7
Biodegradation of poly(ethylene adipate) microcapsules in physiological media; Atkins TW; Spherical reservoir-type microcapsules fabricated using a water/oil/water (W/O/W) double emulsion technique with solvent evaporation and composed of poly(ethylene adipate) (PEAD) blended with 20% poly-epsilon-caprolactone (PCL II) containing a range of bovine serum albumin (BSA) loadings were incubated in Hank's buffer, pH 7.4, newborn calf serum, 1.5% pancreatin and synthetic gastric juice containing 10% pepsin A over 30 days and their percentage weight loss (PWL) and changes in ultrastructural morphology monitored by gravimetry and stereoscan electron microscopy (SEM) respectively . The greatest PWL from microcapsules was observed after incubation in newborn calf serum (NCS) and pancreatin and decreased in the order NCS > pancreatin > synthetic gastric juice > Hank's buffer . Only microcapsules theoretically loaded with 5-20% BSA and incubated in synthetic gastric juice showed a significant increase in PWL with increasing percentage BSA loading . The structural biodegradation of PEAD microcapsules in both Hank's buffer and synthetic gastric juice was minimal whilst the morphological changes observed during incubation in NCS involved pitting of the membrane, some surface erosion and reduction in diameter, followed by microcapsule membrane disruption and loss of reservoir contents . Biodegradation in pancreatin was associated with surface flaking and loss of large fragments of the microcapsule membrane . Only in NCS and pancreatin, where one would expect to see the effects of enzyme activity in addition to simple ester hydrolysis, did biodegradation proceed to the stage where there was a loss of spherical shape and almost total disruption of the microcapsule structure within 30 days.

J Chromatogr A, 1998 Jun 5, 809(1-2), 89 - 107
Comparison of oil composition changes due to biodegradation and physical weathering in different oils; Wang Z et al.; The well-characterized Alberta Sweet Mixed Blend oil and several other oils which are commonly transported in Canada were physically weathered and then incubated with a defined microbial inoculum . The purpose was to produce quantitative data on oil components and component groups which are more susceptible or resistant to biodegradation, and to determine how oils rank in relation to each other in terms of biodegradation potential . The biodegraded oils were characterized by quantitative determination of changes in important hydrocarbon groups including the total petroleum hydrocarbons, total saturates and aromatics, and also by quantitation of more than 100 individual target aliphatic, aromatic and biomarker components . The study reveals a pattern of distinct oil composition changes due to biodegradation, which is significantly different from the pattern due to physical or short-term weathering . It is important to be able to distinguish between these two forms of loss, so that loss due to weathering is not interpreted as loss due to biodegradation in the laboratory or in the field . Based on these findings, the oil composition changes due to biodegradation can be readily differentiated from those due to physical weathering . To rank the tested oils with respect to biodegradability, losses in total petroleum hydrocarbons and aromatics were used to calculate biodegradation potential indices, employing equations proposed by Environment Canada and the US National Oceanic and Atmospheric Administration . The different methods produced very similar biodegradation trends, confirming that patterns of oil biodegradability do exist.

Chemosphere, 1998 Aug, 37(3), 541 - 8
Biodegradation of the herbicide Diuron in soil by indigenous actinomycetes; Esposito E et al.; Three actinomycete strains isolated from soil treated with 2,4-D were able to degrade the herbicide Diuron in vitro . Strain CCT 4916 was the most efficient, degrading up to 37% of applied Diuron (100 mg Kg-1 soil) in 7 days, as measured by HPLC and UV/VIS spectroscopy . All strains showed protease and urease activity; intracellular activity of metapyrocatechase and pyrocatechase were not found . Actinomycete strain CCT 4916 produced manganese peroxidase, which could be potentially related to degradation of Diuron.

Chemosphere, 1998 Aug, 37(3), 523 - 30
Biodegradation of anthracene by soil fungi . Groupe pour l'Etude du Devenir des Xénobiotiques dans l'Environnement (GEDEXE); Krivobok S et al.; A selection of 39 strains of micromycetes known as good degraders of polychlorinated aromatic compounds, mostly isolated from soil and belonging to various taxonomic groups, have been investigated for anthracene degradation . Toxicity and consumption assays, first evaluated on solid media, have not shown any toxicity of anthracene (1-100 mg.L-1) towards fungi . Degradation of anthracene (10 mg.L-1) was then investigated in a liquid synthetic medium for 4 days and evaluated by HPLC . Among the 39 strains tested, 19 degraded anthracene at 50% or more . Zygomycetes appeared to be the most efficient group (mean degradation : 81%) while Melanconiales were the least efficient (mean: 14%) . Among 19 efficient strains, 8 had not yet been reported in the literature: Cryphonectria parasitica, Ceriporiopsis subvermispora, Oxysporus sp., Cladosporium herbarum, Drechslera spicifera, Verticillium lecanii, Fusarium moniliforme var . subglutinans and Rhizopus arrhizus.

Protein Sci, 1998 Jun, 7(6), 1286 - 93
Crystal structure of cis-biphenyl-2,3-dihydrodiol-2,3-dehydrogenase from a PCB degrader at 2.0 A resolution; Hulsmeyer M et al.; cis-Biphenyl-2,3-dihydrodiol-2,3-dehydrogenase (BphB) is involved in the aerobic biodegradation of polychlorinated biphenyls (PCBs) . The crystal structure of the NAD+-enzyme complex was determined by molecular replacement and refined to an R-value of 17.9% at 2.0 A . As a member of the short-chain alcohol dehydrogenase/reductase (SDR) family, the overall protein fold and positioning of the catalytic triad in BphB are very similar to those observed in other SDR enzymes, although small differences occur in the cofactor binding site . Modeling studies indicate that the substrate is bound in a deep hydrophobic cleft close to the nicotinamide moiety of the NAD+ cofactor . These studies further suggest that Asn143 is a key determinant of substrate specificity . A two-step reaction mechanism is proposed for cis-dihydrodiol dehydrogenases.

Chemosphere, 1998 Jul, 37(2), 257 - 64
Kinetics of biodegradation of di-n-butyl phthalate in continuous culture system; Wang J et al.; The characteristics of microbial growth and kinetics of DBP biodegradation was studied in a continuous culture system using DBP as a sole source of carbon . The results showed that, at high substrate concentration, the microbial growth was inhibited by DBP, and can be described by the Haldane model . Kinetic parameters based on Haldane substrate inhibition were evaluated . The values were mu(m) = 0.38 h-1, Ki = 86 mg/l, Ks = 28 mg/l . The DBP concentration to avoid substrate inhibition was inferred theoretically and determined to be 49 mg/L.

Appl Microbiol Biotechnol, 1998 May, 49(5), 573 - 8
Phosphate-independent expression of the carbon-phosphorus lyase activity of Escherichia coli; Yakovleva GM et al.; On the basis of mutational analysis, the genes for phosphonate uptake and degradation in Escherichia coli were shown to be organized in a 10.9-kb operon of 14 genes (named phnC to phnP) and induced by phosphate (P(i)) starvation {Metcalf and Wanner (1993) J Bacteriol 175: 3430-3442} . The repression of phosphonate utilization by P(i) has hindered both the biochemical characterization of the carbon-phosphorus (C-P) lyase activity and the development of improved methods for phosphonate biodegradation in biotechnology . We have cloned the genes phnG to phnP (associated with C-P lyase activity) with the lac promoter to provide expression of C-P lyase in the presence of P(i) . A number of strains lacking portions of the phn operon have been constructed . In vivo complementation of the strains, in which phnC to phnP (including both Pn transport and catalysis genes) or phnH to phnP (including only catalysis genes) was deleted, with plasmids carrying various fragments of the phn operon revealed that the expression of phnC-phnP gene products is essential to restore growth on minimal medium with phosphonate as the sole phosphorus source, while phnG-phnM gene products are required for C-P lyase activity as assessed by in vivo methane production from methylphosphonic acid . The minimum size of the DNA required for the whole-cell C-P lyase activity has been determined to be a 5.8-kb fragment, encompassing the phnG to phnM genes . Therefore, there is no requirement for the phn CDE-encoded phosphate transport system, suggesting that cleavage of the C-P bond may occur on the outer surface of the inner membrane of E . coli cells, releasing the carbon moiety into the periplasm . These data are in agreement with the observation that phosphonates cannot serve as the carbon source for E . coli growth.

J Biomed Mater Res, 1998 Aug, 41(2), 192 - 201
Biocompatibility of poly(etherurethane urea) containing dehydroepiandrosterone; Collier T et al.; Poly(etherurethane urea) (PEUU) elastomers, with their broad range of mechanical properties and high biocompatibility, are used clinically for medical applications . However, the possibility exists for the ether soft segment of PEUU to degrade in long-term uses . To retard degradation, antioxidants that scavenge reactive oxygen intermediates are added . In this study, we incorporated dehydroepiandrosterone (DHEA), which functions by the alternate mechanism of modulating or down-regulating adherent macrophage activity, to retard the biodegradation of PEUUs . Biocompatibility of PEUU samples containing 1% DHEA, 5% DHEA, and 5% vitamin E (alpha-tocopherol) by weight were studied in vivo and in vitro . The biocompatibility was initially evaluated by examination of the inflammatory cellular exudate . Compared to PEUU without additives and PEUU with 5% vitamin E, the addition of 5% DHEA to PEUU caused a decrease in the total leukocyte exudate concentration at 4 days . The addition of 5% DHEA also caused lower macrophage adhesion and FBGC formation compared to the other materials at 7 days . Despite these short-term effects, the biocompatibility at later time points (14, 21, and 70 days) was similar for all materials . Transmission infrared analysis of the materials revealed that more than 70% of the DHEA had leached out of the samples by 3 days implantation . Furthermore, through attenuated total reflectance Fourier transform analysis and scanning electron microscopy, it was determined that unlike vitamin E, DHEA did not enhance long-term PEUU biostability . The effect of DHEA on inflammatory cell activity appeared to be dose dependent, with improved biocompatibility in vivo for higher loading levels of DHEA, but the overall effect was limited owing to the rapid diffusion of the water-soluble DHEA from the PEUU.

Chemosphere, 1998 Jul, 37(1), 103 - 11
Pentachlorophenol and phenanthrene biodegradation in creosote contaminated aquifer material; Mohammed SA et al.; Contamination of the subsurface environment at the Libby Superfund Site, Montana, includes polycyclic aromatic hydrocarbons and f1p4achlorophenol due to accidental spills and improper disposal of wood preserving wastes . Biodegradation is a treatment technology gaining wide application in the treatment of hazardous waste sites . A microcosm study was conducted to evaluate the effect of temperature, sampling depth, nutrient addition, and oxygen on the biodegradation potential of phenanthrene and pentachlorophenol in aquifer samples using radiolabeled chemicals . Mineralization of phenanthrene reached 14% but was less than 1% for pentachlorophenol over the 56 day incubation period . Phenanthrene mineralization in microcosms at 10 degrees C was not significantly different from those at 20 degrees C . This may have been due to microbial community acclimation to lower temperatures at the site . Average volatilization was less than 2% for both phenanthrene and pentachlorophenol . After 56 days, most of the radiolabeled chemical was either solvent extractable or soil bound.

J Capillary Electrophor, 1997 Jul-Aug, 4(4), 189 - 94
Analysis of the transformation of nitroaromatic compounds in wastewater by bacteria using micellar electrokinetic capillary chromatography; Chow TM et al.; A rapid micellar electrokinetic capillary chromatographic method is described for the analysis of nitroaromatic and nitramine explosives using sodium dodecyl sulfate-borate buffer with application to analyze specifically the biodegradation products of trinitrotoluene . The method is fast, in expensive, offers better resolution, and saves on the consumption of organic solvents used in a comparable reversed-phase HPLC method.

Ecotoxicol Environ Saf, 1998 May-Jun, 40(1-2), 94 - 6
Selection of a pesticide with low environmental impact; Tykva R; The conditions were analyzed for evaluation of a mean soil biodegradation of a pesticide within a certain region . Different soils from two Czech and two German regions were used for a highly sensitive analysis based on a laboratory incubation of each isolated active soil strain with a radiolabeled pesticide . It was proved for all analyzed soils that the biodegradation activity of the total biomass was caused by only a small part of the present microbial strains . Not only bacteria, but also fungi and yeast have to be taken into consideration in a pesticide biodegradation . The biodegradation products were quantified by radio high-performance liquid chromatography.

Ecotoxicol Environ Saf, 1998 May-Jun, 40(1-2), 19 - 28
Biodegradation: selection of suitable model; Cetkauskaite A et al.; Biodegradation of five herbicides, two acetanilides (propanil and propachlor), and three phenylureas (diuron, monuron, and fenuron) was analyzed in samples of river water during a period of 6-8 weeks . Concentrations of 0.2-5.0 mg/liter of the herbicides were used for biodegradation . Two types of river water samples with different numbers of microorganisms were collected from the Neris River: upstream and downstream of the city of Vilnius . The initial concentration of microorganisms varied from 4.7 x 10(5) to 2.7 x 10(6) cells/liter and from 1.4 x 10(8) to 5.3 x 10(8) cells/liter in water samples from the Neris River upstream and downstream of Vilnius, respectively . Chemical analysis was performed by the HPLC technique, using standards of herbicides and likely degradation products . Chemical parameters of different river water samples used in biodegradation experiments were analyzed . A second-order reaction rate model was used for the analysis of biodegradation data . Values of the first-order rate constants (Ka) revealed the following decrease in the biodegradation rate of herbicides: propanil >> diuron > or = monuron = propachlor > fenuron . This sequence was constant for all water samples analyzed . The set of decreasing value of second-order biodegradation rate constants (Kb) differed from the set of first-order constants (Ka) because the total number of bacteria in the water samples varied by up to two orders of magnitude, and this variation influenced the calculated values of Kb . Thus, different sets of Kb values were obtained for the water samples from the river upstream and downstream of the city . Schemes of a variety of biodegradation models are presented, and the suitability of the second-order reaction rate model for the description of biodegradation of xenobiotics is discussed.

Appl Microbiol Biotechnol, 1998 Apr, 49(4), 475 - 81
Kinetics of biodegradation of gasoline and its hydrocarbon constituents; Yerushalmi L et al.; Aerobic biodegradation of gasoline and its constituents, benzene, toluene and ethylbenzene were studied by an enrichment from soil indigenous microbial population . The enrichment culture completely degraded 16.1-660 mg/l gasoline in 2.5-16 days respectively, without accumulation of any by-products . The kinetics of gasoline as well as benzene, toluene and ethylbenzene biodegradation was investigated with initial gasoline concentrations of 16.1-62.6 mg/l . The maximum specific rates of biodegradation of benzene, toluene and ethylbenzene were 0.12, 0.38 and 0.19 mg mg biomass-1 day-1 respectively . When benzene and toluene were used as sole substrate, the maximum specific rates of their biodegradation were 62.9 and 16.4 times greater than the corresponding values for a mixture (gasoline) . The microbial culture was able to mineralize up to 200 mg/l pure toluene and benzene . Maximum mineralization efficiencies of benzene and toluene were 76.7 +/- 5.1% and 76.8 +/- 1.3% respectively . Self-inhibition and competitive inhibition patterns were observed during the biodegradation of benzene and toluene alone and in the mixture respectively . The observed kinetics was modeled according to Andrews' inhibition model.

Appl Environ Microbiol, 1998 Jun, 64(6), 2200 - 6
Characterization of metabolites in the biotransformation of 2,4,6-trinitrotoluene with anaerobic sludge: role of triaminotoluene; Hawari J et al.; The present study describes the biotransformation of 2,4,6-trinitrotoluene (TNT) (220 microM) by using anaerobic sludge (10%, vol/vol) supplemented with molasses (3.3 g/liter) . Despite the disappearance of TNT in less than 15 h, roughly 0.1% of TNT was attributed to mineralization (14CO2) . A combination of solid-phase microextraction-gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry identified two distinctive cycles in the degradation of TNT . One cycle was responsible for the stepwise reduction of TNT to eventually produce triaminotoluene (TAT) in relatively high yield (160 microM) . The other cycle involved TAT and was responsible for the production of azo derivatives, e.g., 2,2',4,4'-tetraamino-6,6'-azotoluene (2,2',4, 4'-TA-6,6'-azoT) and 2,2',6,6'-tetraamino-4,4'-azotoluene (2,2',6, 6'-TA-4,4'-azoT) at pH 7.2 . These azo compounds were also detected when TAT was treated with the anaerobic sludge but not with an autoclaved sludge, suggesting the biotic nature of their formation . When the anaerobic conditions in the TAT-containing culture medium were removed by aeration and/or acidification (pH 3), the corresponding phenolic compounds, e.g., hydroxy-diaminotoluenes and dihydroxy-aminotoluenes, were observed at room temperature . Trihydroxytoluene was detected only after heating TAT in water at 100 degrees C . When 13CH3-labeled TNT was used as the N source in the above microcosms, we were unable to detect 13C-labeled p-cresol or {13CH3}toluene, indicating the absence of denitration or deamination in the biodegradation process . The formation and disappearance of TAT were not accompanied by mineralization, suggesting that TAT acted as a dead-end metabolite.

Appl Environ Microbiol, 1998 Jun, 64(6), 2141 - 6
Cometabolism of 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene by Pseudomonas acidovorans M3GY grown on biphenyl; Hay AG et al.; 1,1-Dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE), a toxic breakdown product of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), has traditionally been viewed as a dead-end metabolite: there are no published reports detailing enzymatic ring fission of DDE by bacteria in either soil or pure culture . In this study, we investigated the ability of Pseudomonas acidovorans M3GY to transform DDE and its unchlorinated analog, 1,1-diphenylethylene (DPE) . While strain M3GY could grow on DPE, cells grown on DPE as a sole carbon source could not degrade DDE . Cells grown on biphenyl, however, did degrade DDE . Mass balance analysis of {14C}DDE showed transformation of more than 40% of the recoverable radioactivity . Nine chlorinated metabolites produced from DDE were identified by gas chromatography-mass spectrometry-Fourier-transform infrared spectrometry (GC-MS-FTIR) from cultures grown on biphenyl . Recovery of these metabolites demonstrates that biphenyl-grown cells degrade DDE through a meta-fission pathway . This study provides a possible model for biodegradation of DDE in soil by biphenyl-utilizing bacteria.

Appl Environ Microbiol, 1998 Jun, 64(6), 2020 - 5
Comparison of gas chromatography and mineralization experiments for measuring loss of selected polychlorinated biphenyl congeners in cultures of white rot fungi; Beaudette LA et al.; Two methods were used to compare the biodegradation of six polychlorinated biphenyl (PCB) congeners by 12 white rot fungi . Four fungi were found to be more active than Phanerochaete chrysosporium ATCC 24725 . Biodegradation of the following congeners was monitored by gas chromatography: 2,3-dichlorobiphenyl, 4,4'-dichlorobiphenyl, 2,4',5-trichlorobiphenyl (2,4',5-TCB), 2,2',4,4'-tetrachlorobiphenyl, 2,2',5,5'-tetrachlorobiphenyl, and 2,2',4,4',5,5'-hexachlorobiphenyl . The congener tested for mineralization was 2,4',5-{U-14C}TCB . Culture supernatants were also assayed for lignin peroxidase and manganese peroxidase activities . Of the fungi tested, two strains of Bjerkandera adusta (UAMH 8258 and UAMH 7308), one strain of Pleurotus ostreatus (UAMH 7964), and Trametes versicolor UAMH 8272 gave the highest biodegradation and mineralization . P . chrysosporium ATCC 24725, a strain frequently used in studies of PCB degradation, gave the lowest mineralization and biodegradation activities of the 12 fungi reported here . Low but detectable levels of lignin peroxidase and manganese peroxidase activity were present in culture supernatants, but no correlation was observed among any combination of PCB congener biodegradation, mineralization, and lignin peroxidase or manganese peroxidase activity . With the exception of P . chrysosporium, congener loss ranged from 40 to 96%; however, these values varied due to nonspecific congener binding to fungal biomass and glassware . Mineralization was much lower, </=11%, because it measures a complete oxidation of at least part of the congener molecule but the results were more consistent and therefore more reliable in assessment of PCB biodegradation.

Biomed Sci Instrum, 1997, 34, 76 - 81
The preliminary study and tentative animal study on the sintered PDLLA/TCP composites as bone fracture internal fixation; Lin FH et al.; Polyesters based on the lactic acid have been reported safety and biodegradation in the human beings for two decades . The greatest advantage of the material is its degradation only conducted by the hydrolysis, where the ester backbones are supposed to be unchained in the aqueous condition . The final degradable products are carbon dioxide and water which can be metabolized and digested in the physiological environment . The goal of this study was aimed to develop a composite sintered with poly-DL-lactide (PDLLA) and tricalcium phosphate (TCP) ceramic particles as orthopedic application . The TCP particles in a range of 30-60 wt% (with 5 wt% increment) were doped into the PDLLA matrix for the reinforcement, which were prepared by the melting and hot pressing techniques . The basic mechanical strength, biodegradable behavior, and biological response of the composites will be investigated in the study . Various techniques, such as pH meter, UV, FTIR, XRD ect., were used to examine and record the degradable process of the composites soaked in the saline for 1-16 weeks . The rabbit femur condyle fracture fixation test was used to evaluate the tissue compatibility and the effects of bone fracture fixation of the composites . The histological observation and x-ray photography were applied for investigating assistance . In the histological evaluation of rabbit femur condyle fracture fixation test, the surface of the composite with 50 wt% TCP addition was attached by the new generated bone without fibrous tissue around after 8 weeks implantation . The fracture bone was gradually healing and the composite always firmly and properly fixed on the fracture area during the implanted period, which provided a breeding environment for normal bone remodeling . The developed composite was thought to be an alternative material for orthopedic application in the future, especially in bone screw and bone plate.

J Oral Maxillofac Surg, 1998 May, 56(5), 604 - 14; discussion 614-5
A 5-year in vitro and in vivo study of the biodegradation of polylactide plates; Suuronen R et al.; PURPOSE: The purpose of this study was to investigate the long-term tissue response and duration of degradation of self-reinforced poly-L-lactide (SR-PLLA) multilayer plates in vivo . MATERIALS AND METHODS: Mandibular osteotomies in sheep were fixed with SR-PLLA multilayer plates . The animals were followed for 1, 2, 3, 4, and 5 years, after which histologic studies were performed . RESULTS: The foreign-body reaction was mainly mild, and the osteotomies were well united . After 5 years in vivo, the material was almost completely resorbed, but small particles of polymer could still be detected at the implantation site . SR-PLLA plates were also incubated in vitro for 5 years . The material degraded considerably faster in vivo than in vitro . Molecular weight, melting temperature, and crystallinity of the plates remained at a constant level after 2 years in vitro, indicating very slow degradation of the oligomeric (molecular weight {Mw}, 3500 daltons), highly crystalline (heat of fusion, 70 J/g), PLLA residue solely as a result of hydrolysis . Although the plates became increasingly fragile as they degraded, they retained their macroscopic form until the end of the 5-year follow-up . Loss of mass of the plates was 52%+/-8% after 5 years of incubation in vitro . CONCLUSIONS: Although the long degradation period may seem to be a minor drawback to the use of such plates, it does not appear to affect the healing process.

Cancer Lett, 1998 Apr 24, 126(2), 173 - 8
The inhibitory effect of vitamin E on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in mice based on the regulation of polyamine metabolism; Kishimoto M et al.; The present study was carried out in order to estimate a usefulness of vitamin E against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in mice . Feeding high doses of vitamin E suppressed the NNK-induced elevation of the activity of ornithine decarboxylase, a key enzyme of polyamine biosynthesis, in the lungs of mice at 4 weeks after injection . In contrast, the vitamin elevated the NNK-induced decrease of the activity of spermidine/spermine N1-acetyltransferase, a key enzyme of polyamine biodegradation . In conjugation with these events, the NNK-increased level of proliferating nuclear cell antigen as a marker of cell proliferation was suppressed by vitamin E treatment . Also, the supply of high doses of vitamin E suppressed NNK-induced lung tumorigenesis in mice . These results suggest that vitamin E inhibits the development of lung tumors in mice treated with NNK, partly due to the regulation of polyamine metabolism.

Acta Paediatr Jpn, 1998 Apr, 40(2), 122 - 30
Helicobacter pylori-dependent intragastric urea biodegradation in children: diagnostic and pathogenetic importance; Nijevitch AA; The objective of the present work was to study the relationship between intragastric urea hydrolysis generated by Helicobacter pylori urease and acid-peptic disease in childhood . Intragastric urease activity was examined by urea and ammonia concentration measurement in gastric juice in 91 children with upper abdominal complaints . Helicobacter pylori infection was detected from 70 (76.9%) of 91 patients, including all of the 15 subjects with peptic ulcer disease . Helicobacter pylori-related gastritis in children was associated with a decrease of urea and an increase of ammonia in gastric juice (P < 0.001) in comparison with H . pylori-negative children . The gastritis score was correlated with the concentrations of urea and ammonia in the gastric juice of patients infected with H . pylori . There was a significant correlation between the histologically detected dissemination of organisms and gastric ammonia levels . Similar results were obtained concerning correlation between gastric juice ammonia and anti-H . pylori specific immunoglobulin G versus highly purified antigen of H . pylori containing urease . Present findings prove that H . pylori plays an essential role in the pathogenesis of gastritis and that ammonia is one of the main pathogenic factors of acid-peptic disease.

J Bacteriol, 1998 May, 180(9), 2502 - 6
A novel 2-aminomuconate deaminase in the nitrobenzene degradation pathway of Pseudomonas pseudoalcaligenes JS45; He Z et al.; 2-Aminomuconate, an intermediate in the metabolism of tryptophan in mammals, is also an intermediate in the biodegradation of nitrobenzene by Pseudomonas pseudoalcaligenes JS45 . Strain JS45 hydrolyzes 2-aminomuconate to 4-oxalocrotonic acid, with the release of ammonia, which serves as the nitrogen source for growth of the microorganism . As an initial step in studying the novel deamination mechanism, we report here the purification and some properties of 2-aminomuconate deaminase . The purified enzyme migrates as a single band with a molecular mass of 16.6 kDa in 15% polyacrylamide gel electrophoresis under denaturing conditions . The estimated molecular mass of the native enzyme was 100 kDa by gel filtration and 4 to 20% gradient nondenaturing polyacrylamide gel electrophoresis, suggesting that the enzyme consists of six identical subunits . The enzyme was stable at room temperature and exhibited optimal activity at pH 6.6 . The Km for 2-aminomuconate was approximately 67 microM, and the Vmax was 125 micromol x min(-1) x mg(-1) . The N-terminal amino acid sequence of the enzyme did not show any significant similarity to any sequence in the databases . The purified enzyme converted 2-aminomuconate directly to 4-oxalocrotonate, rather than 2-hydroxymuconate, which suggests that the deamination was carried out via an imine intermediate.

Appl Environ Microbiol, 1998 May, 64(5), 1715 - 20
Two new Mycobacterium strains and their role in toluene degradation in a contaminated stream; Tay ST et al.; Two toluene-degrading strains, T103 and T104, were isolated from rock surface biomass in a freshwater stream contaminated with toluene . The strains exhibit different capacities for degradation of toluene and other aromatic compounds and have characteristics of the genus Mycobacterium . Both are aerobic, rod-shaped, gram-positive, nonmotile, and acid-alcohol fast and produce yellow pigments . They have mainly straight-chain saturated and monounsaturated fatty acids with 10 to 20 carbon atoms and large amounts of tuberculostearic acid that are typical of mycobacteria . Fatty acid analyses indicate that T103 and T104 are different mycobacterial strains that are related at the subspecies level . Their identical 16S rDNA sequences are most similar to Mycobacterium aurum and Mycobacterium komossense, and they constitute a new species of fast-growing mycobacteria . Ecological studies reveal that toluene contamination has enriched for toluene-degrading bacteria in the epilithic microbial community . Strains T103 and T104 play only a small role in toluene degradation in the stream, although they are present in the habitat and can degrade toluene . Other microorganisms are consequently implicated in the biodegradation.

Chemosphere, 1998 Apr, 36(10), 2211 - 24
The use of 13C-labelled polycyclic aromatic hydrocarbons for the analysis of their transformation in soil; Richnow HH et al.; The formation of non-extractable residues during biodegradation and humification processes in soils and sediments represents a major sink for organic contaminants . The mode of incorporation of polycyclic aromatic hydrocarbons (PAH) and their metabolites into macromolecular organic matter during microbial degradation was studied applying 13C-labelled compounds . Mineralisation rates were determined by measuring the 13CO2 production . An incorporation of 13C-PAH-fragments into humic material could be traced by isotopic analysis of the bulk organic matter . Furthermore, selective chemical degradation reactions were performed to analyse the precise chemical structure of covalently bound 13C-labelled PAH fragments in soil humic substances . Structural assignments by GC-MS combined with isotope measurements on the bulk organic carbon and at the molecular level (Isotope Ratio Monitoring-GC-MS) provided useful information on the fate of xenobiotics within the soil.

Chemosphere, 1998 Apr, 36(10), 2149 - 73
A review of the environmental fate, effects, and exposures of bisphenol A; Staples CA et al.; Bisphenol A (CAS 85-05-7) may be released into the environment through its use and handling, and permitted discharges . BPA is moderately soluble (120 to 300 mg/L at pH 7), may adsorb to sediment (Koc 314 to 1524), has low volatility, and is not persistent based on its rapid biodegradation in acclimated wastewater treatment plants and receiving waters (half-lives 2.5 to 4 days) . BPA is "slightly to moderately" toxic (algal EC50 of 1000 micrograms/L) and has low potential for bioaccumulation in aquatic organisms (BCFs 5 to 68) . The chronic NOEC for Daphnia magna is > 3146 micrograms/L . Surface water concentrations are at least one to several orders of magnitude lower than chronic effects, with most levels nondetected.

Crit Rev Microbiol, 1998, 24(1), 1 - 22
Biodegradation of the acetanilide herbicides alachlor, metolachlor, and propachlor; Stamper DM et al.; Alachlor, metolachlor, and propachlor are detoxified in biological systems by the formation of glutathione-acetanilide conjugates . This conjugation is mediated by glutathione-S-transferase, which is present in microorganisms, plants, and mammals . Other organic sulfides and inorganic sulfide also react through a nucleophilic attack on the 2-chloro group of acetanilide herbicides, but the products are only partially characterized . Sorption in soils and sediments is an important factor controlling the migration and bioavailability of these herbicides, while microbial degradation is the most important factor in determining their overall fate in the environment . The biodegradation of alachlor and metolachlor is proposed to be only partial and primarily cometabolic, and the ring cleavage seems to be slow or insignificant . Propachlor biodegradation has been reported to proceed to substantial (> 50%) mineralization of the ring structure . Reductive dechlorination may be one of the initial breakdown mechanisms under anaerobic conditions . Aerobic and anaerobic transformation products vary in their polarity and therefore in soil binding coefficient . A catabolic pathway for chloroacetanilide herbicides has not been presented in the literature because of the lack of mineralization data under defined cultural conditions.

J Biomed Mater Res, 1998 May, 40(2), 336 - 40
Polymyxin B inhibits biphasic calcium phosphate degradation induced by lipopolysaccharide-activated human monocytes/macrophages; Kimakhe S et al.; Numerous cell types, such as monocytes and osteoclasts, are involved in calcified matrix degradation . In this context, calcium-phosphate ceramics present similar degradation processes in vivo and in vitro to those found in a natural calcified substrate . As the monocyte/macrophage lineage is among the first cells to appear in ceramic implantation sites, it is a key protagonist in inflammatory reaction and biodegradation mechanisms . This study investigated the ability of human monocytes/macrophages activated by various agents {lipopolysaccharides (LPS), polymyxin B (PMB)} to degrade biphasic calcium-phosphate ceramics . PMB sulfate is a bacteriostatic antibiotic that modulates LPS-induced cell activities in vivo and in vitro . Degradation pits (about 10 microns) produced on the pellet surface by these monocytes were discrete, with well defined margins . LPS increased the degradation of calcium-phosphate ceramic (number of lacunae, mean pellet surface area degraded) in a dose-dependent manner whereas polymyxin B downmodulated it significantly . The addition of 2 micrograms/mL of polymyxin B reduced the number of degradation lacunae and the extent of degraded surface area induced by 0.1 microgram/mL LPS by 87% and 64%, respectively . Thus this cell culture system can be very useful in the study of cellular degradation of biomaterials and of the influence of therapeutic agents that may modulate these cell activities.

Curr Microbiol, 1998 Mar, 36(3), 136 - 47
Microbial growth in a steady-state model of ethylene glycol-contaminated soil; McVicker L et al.; Biodegradation of ethylene glycol was tested in a laboratory-scale, steady-state infiltration system of two arid region soil types by monitoring indigenous microbial growth after the infiltration of three concentrations of ethylene glycol . Microorganisms in the soils were able to adapt to the ethylene glycol in several cases, resulting in higher numbers of microorganisms and lower pHs in the effluents . These microorganisms were identified and were able to use ethylene glycol as a sole carbon source . The adaptation was seen best with high-moisture-content soils when the ethylene glycol concentrations were 1% or 10% . However, acclimation to 0.1% and 10% ethylene glycol did not occur in low-moisture-content clay soil, but did occur in low-moisture-content silt soil, indicating that soil type and moisture content are important factors . In all cases, microbial diversity decreased over time.

Appl Environ Microbiol, 1998 Apr, 64(4), 1256 - 63
19F nuclear magnetic resonance as a tool to investigate microbial degradation of fluorophenols to fluorocatechols and fluoromuconates; Boersma MG et al.; A method was developed to study the biodegradation and oxidative biodehalogenation of fluorinated phenols by 19F nuclear magnetic resonance (NMR) . Characterization of the 19F NMR spectra of metabolite profiles of a series of fluorophenols, converted by purified phenol hydroxylase, catechol 1,2-dioxygenase, and/or by the yeast-like fungus Exophiala jeanselmei, provided possibilities for identification of the 19F NMR chemical shift values of fluorinated catechol and muconate metabolites . As an example, the 19F NMR method thus defined was used to characterize the time-dependent metabolite profiles of various halophenols in either cell extracts or in incubations with whole cells of E . jeanselmei . The results obtained for these two systems are similar, except for the level of muconates observed . Altogether, the results of the present study describe a 19F NMR method which provides an efficient tool for elucidating the metabolic pathways for conversion of fluorine-containing phenols by microorganisms, with special emphasis on possibilities for biodehalogenation and detection of the type of fluorocatechols and fluoromuconates involved . In addition, the method provides possibilities for studying metabolic pathways in vivo in whole cells.

Appl Microbiol Biotechnol, 1998 Feb, 49(2), 202 - 9
The effect of growth conditions on the biodegradation of tributyl phosphate and potential for the remediation of acid mine drainage waters by a naturally-occurring mixed microbial culture; Thomas RA et al.; The biodegradation of tributyl phosphate (Bu3-P, TBP), releasing phosphate at a high enough concentration locally to precipitate uranium from solution, was demonstrated by a mixed culture consisting primarily of pseudomonads . The effect of various parameters on Bu3-P biodegradation by growing cells is described . Growth at the expense of Bu3-P as the carbon and phosphorus source occurred over a pH range from 6.5 to 8, and optimally at pH 7 . Bu3-P biodegradation was optimal at 30 degrees C, reduced at 20 degrees C and negligible at 4 degrees C and 37 degrees C . Incorporation of Cu or Cd inhibited, and Ni, Co and Mn reduced its degradation . Inorganic phosphate (above 10 mM) and kerosene (up to 1 g/l) reduced Bu3-P biodegradation significantly, but nitrate had no effect . Sulphate (10-100 mM) was inhibitory . When pregrown biomass was used the fastest rates of tributyl and dibutyl phosphate biodegradation were 25 mumol h-1 mg protein-1 and 37 mumol h-1 mg protein-1 respectively . Microcarrier-immobilised biomass decontaminated uranium-bearing acid mine waste water by uranium phosphate precipitation at the expense of Bu3-P hydrolysis in the presence of 35 mM SO(4)2- . At pH 4.5, 79% of the UO2(2)+ was removed at a flow rate of 1.4 ml/h on a 7-ml.test column.

J Submicrosc Cytol Pathol, 1998 Jan, 30(1), 157 - 63
Interaction of PCB congeners and 2,3,7,8-TCDD in the rat liver: an electron microscope study; Connell BJ et al.; Polyhalogenated aromatic compounds such as polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins continue to be environmental contaminants because of their bioaccumulation in the food chain and resistance to biodegradation . This study was undertaken to determine if WHO-IPCS PCB congeners or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) individually or their coadministration in rats produced morphological alterations in the liver . Groups (N = 5) of female Sprague Dawley rats received TCDD (0, 2.5, 25, 250, 1,000 ng/kg bw/day) or PCB (0, 2, 20 micrograms/kg bw/day) either alone, or each dose of PCB coadministered with that of TCDD . The test substances were dissolved in corn oil and given by gavage at 0.2 ml/100 g bw/day for 28 days . At the end of the experiment the rats were killed and liver samples were prepared for transmission electron microscopy . Electron micrographs of the liver from animals of the control groups revealed characteristic normal hepatocyte architecture . An increase in smooth endoplasmic reticulum (SER) profiles and a corresponding decrease in the profiles of rough endoplasmic reticulum (RER) proportional to the increased doses of the compounds was revealed in the micrographs . Coadministration of PCBs and TCDD induced greater SER proliferation and a greater decrease in the number of RER profiles compared to either compound administered individually . The PCBs and TCDD at the doses used apparently interacted to induce hepatic ultrastructural alterations . These changes may represent an attempt by the organism to metabolize and neutralize the effects of xenobiotics.

Plant Mol Biol, 1998 Apr, 36(6), 909 - 15
Apple messenger RNAs related to bacterial lignostilbene dioxygenase and plant SAUR genes are preferentially expressed in flowers; Watillon B et al.; In an attempt to use a differential display procedure to identify organ-specific genes in apple, cDNA fragments of two transcripts preferentially expressed in flowers were isolated and corresponding full-length cDNA inserts were subsequently obtained . One of these clones, Md-FS1, belongs to the SAUR gene family, originally identified as a set of auxin-inducible genes in soybean . The second one, Md-FS2, encodes a polypeptide with sequence similarities to bacterial lignostilbene-alpha,beta-dioxygenase isozymes, which are thought to be involved in lignin biodegradation . Northern blot analysis confirmed that both genes are preferentially expressed in floral organs at full bloom, while being expressed at lower or undetectable levels in vegetative organs (leaves, shoots or roots) as well as in immature, green and unopened blossoms . Furthermore, Md-FS1 transcripts also appeared to accumulate in vegetative tissues after auxin treatment of micropropagated apple shoots.

Am J Rhinol, 1998 Jan-Feb, 12(1), 27 - 31
Induction in vivo of cartilage grafts for craniofacial reconstruction; Verwoerd-Verhoef HL et al.; In the craniofacial region, defects of cartilage structures are preferably reconstructed with autologous cartilage . Donor-site morbidity related to the creation of a new defect elsewhere, and a lack of growth potential of the graft--mandatory in children--have stimulated investigators to find other ways to generate new "extra" cartilage . Several biomaterials have been tested as a matrix for the ingrowth of (peri)chondroblasts in experimental animals . In young (growing) rabbits we have developed a process of heterotopic cartilage induction with the use of a demineralized (bovine) bone matrix which is enfolded in a pedicled flap of ear perichondrium for at least three weeks . During this period the demineralized matrix is colonized by macrophages and polymorphonuclear cells which start a process of complete biodegradation of the material . Simultaneously, the collagen matrix is invaded by mesenchymal cells, originating from the perichondrium and differentiating into chondroblasts and later, into chondrocytes forming the intercellular substance . The developing, very young cartilage could be demonstrated as collagen type II, thus, hyaline cartilage . When applied with its adherent perichondrium as a graft, it merges easily with the more matured host cartilage and even appears to be capable of further growth . Therefore, it seems suitable for the reconstruction of a cartilaginous defect in growing cartilaginous structures like the nasal septum or the larynx.

Cesk Slov Oftalmol, 1998 Jan, 54(1), 36 - 40
{Biodegradation of silicone drainage tubes in the efferent lacrimal system}; Kominek P et al.; The authors present an account on their experience with biodegradation of silicone cannulas used for drainage of the efferent lacrimal system . They examined by means of a light microscope (enlargement up to 140 x) 38 cannulas, inserted into the lacrimal pathways for 1-7 months . They did not observe any biological damage of the surface of the cannula, not even when compared with non-exposed cannulas . Microbiological examination of six exposed cannulas did not reveal fungal infestation . The lacrimal pathways are not an aggressive environment for temporary cannulas.

J Biomater Sci Polym Ed, 1997, 9(1), 75 - 87
Synthesis, characterization, biodegradation, and drug delivery application of biodegradable lactic/glycolic acid oligomers: Part II . Biodegradation and drug delivery application; Wang N et al.; Previously synthesized lactic/glycolic acid (PLGA) oligomers with different compositions (i.e . different ratio of lactic to glycolic acid in the oligomers) were further studied regarding their biodegradation and drug delivery application . The PLGA oligomers have fast biodegradation characteristics . They degrade to water soluble substances, i.e . lactic and glycolic acids, at a rate of 31.43-40.68 mg day-1 in a medium of constant pH and 28.04-37.87 mg day-1 in a medium of non-constant pH . The biodegradation rate is affected by the composition of the PLGA oligomers and the pH of the incubating medium . The higher the content of glycolic acid moiety in the oligomer, the faster the biodegradation rate . The lower the pH of the incubating medium, the slower the biodegradation of PLGA oligomers . A sustained-release drug delivery system based on the PLGA oligomers was fabricated as injectable microgranules by thermal blending of the PLGA oligomers and drug . Aspirin was used as a model drug . The oligomeric microgranules have advantages of easy fabrication, high drug loading efficiency, easy administration, and fast biodegradation . This thermal blending preparation method has a high loading efficiency of more than 90% . The PLGA oligomeric microgranules can release drug from 9 to 13 days depending on the oligomer composition . Both drug release rate and release duration are influenced by composition of the oligomers . The PLGA oligomeric matrix has the capability of protecting aspirin from hydrolysis . The lactic/glycolic acid oligomeric microgranules have potential use for sustained-release drug delivery.

Chemosphere, 1998 Mar, 36(6), 1319 - 43
Terrestrial risk assessment for linear alkyl benzene sulfonate (LAS) in sludge-amended soils; de Wolf W et al.; A comparison of the estimated environmental concentration and the effect concentrations (in the laboratory or field) in the receiving compartment form the basis of environmental risk assessments . This paper reviews processes that critically influence the fate of LAS in the terrestrial environment . Concentrations of LAS in sludge are quite high due to sorption to primary sludge, precipitation of Ca and Mg-salts of LAS, and lack of biodegradation under anaerobic digestion . This implies that when sludge is applied to soil e.g . as a fertilizer, considerable amounts of this important surfactant may enter the terrestrial environment . Influence of aerobic situations on LAS concentrations during sludge storage needs further research to allow incorporation into the risk assessment . Aerobic biodegradation in soil is considered the most important removal mechanism of LAS loading to the terrestrial environment through sludge-amendment . Sorption plays a role in determining the residence time of a chemical in the soil, hereby enabling more time for biodegradation to occur . In addition, sorption may affect the expression of effects of surfactants towards benthic and soil dwelling organisms and plants . Another factor that needs further attention is the form of LAS in the environment, which is not similar to the commercial material applied in detergents . The differential sorption and biodegradation of the LAS components lead to a shift in the alkyl chain length (homologue), and phenylisomer distribution towards increased hydrophobicity . Also, occurrence of Ca/Mg-salts in the environment versus the Na-salt for the commercial material critically impacts the extrapolation of effects data obtained in lab studies (mostly performed with the commercial material) to the field . The literature data were used in combination with strategies and methods provided by the European Union Technical Guidance Document in support of risk assessment of new and notified substances (1996) for the prediction of environmental concentrations of LAS entering the soil system through sludge applications . Soil biodegradation is an essential, necessary element for the PEC-calculations of LAS . The initial realistic worst case assessment presented indicates no human health risks exists with indirect exposure to LAS through either food or drinking water . Also, current LAS use does not pose a risk to terrestrial organisms such as plants and invertebrates.

Chemosphere, 1998 Mar, 36(6), 1211 - 32
A study of the degradation of phenoxyacid herbicides at different sites in a limestone aquifer; Harrison I et al.; The biodegradation of three phenoxyalkanoic acid herbicides, viz . MCPA, dichlorprop and mecoprop, under aerobic and anaerobic conditions was investigated using microcosm techniques . The field studies were conducted in a limestone aquifer that had suffered contamination from leaking landfill sites in which phenoxyalkanoic acid herbicides (mostly mecoprop) had undergone disposal . The results from in situ field and laboratory microcosms indicated that under microbially active aerobic conditions the biotransformation of all three herbicides was rapid and that lag phases were short . Under fully aerobic conditions the concentration of each of the three herbicides was reduced from 2,000 micrograms/l to below the detection limit (approx . 10 micrograms/l) of the HPLC system, used for their analysis, within 14 days . However, under microbially active anaerobic conditions no degradation of the herbicides could be discerned over the 100-200 day duration of the experiments . This finding has significant implications for the disposal of phenoxyalkanoic acid herbicides particularly in situations where any resulting leachate may find its way into underlying water resources.

J Biomed Mater Res, 1998 Mar 15, 39(4), 650 - 9
Biodegradation in vitro and retention in the rabbit eye of crosslinked poly(1-vinyl-2-pyrrolidinone) hydrogel as a vitreous substitute; Hong Y et al.; To elucidate the relatively short retention of crosslinked poly(1-vinyl-2-pyrrolidinone) hydrogels in the eye when used as potential vitreous substitutes, a 14C-labeled hydrogel was produced and subjected to both in vitro biodegradation assays and in vivo experiments . The polymer was synthesized by the free-radical copolymerization of 99% 1-vinyl-2-pyrrolidinone with 1% 14C-methyl methacrylate in the presence of ethylene glycol dimethacrylate (0.1%) as crosslinking agent . The in vitro protocol for assessing the biodegradation included the incubation of hydrogel with hydrolases (trypsin or collagenase), followed by examination of changes in its physical characteristics and by monitoring its residual radioactivity, as well as by detection of possible degradation products . Within the maximum duration of experiments (4 weeks), none of the procedures indicated biodegradation of polymer . The hydrogel was also injected into the vitreous humor of rabbits and followed up to 4 weeks . Residual radioactivity measurements of the vitreous contents indicated that 50% of the polymer was removed by the end of this period . Histopathologic examination revealed cell infiltrates of the mononuclear phagocyte system in both vitreous and retinal tissue . A possible phagocyte-mediated mechanism for the dissipation of hydrogel is discussed.

J Environ Sci Health B, 1998 Jan, 33(1), 17 - 36
Bacterial degradation of homo- and heterocyclic aromatic compounds in the presence of soluble/colloidal humic acid; Meredith CE et al.; Aqueous association of several organic compounds to Aldrich humic acid (AHA) was determined by equilibrium dialysis or solubility enhancement . The effect of varying concentrations of AHA on chemical degradation was also determined in batch experiments . Atrazine and glucose mineralization was greater in the presence of AHA and the enhancement was attributed to enhanced cellular uptake . No AHA inhibition on naphthalene or quinoline biodegradation was observed.

Appl Environ Microbiol, 1997 Oct, 63(10), 3911 - 5
Dehalogenation and biodegradation of brominated phenols and benzoic acids under iron-reducing, sulfidogenic, and methanogenic conditions; Monserrate E et al.; The anaerobic biodegradation of monobrominated phenols and benzoic acids by microorganisms enriched from marine and estuarine sediments was determined in the presence of different electron acceptors {i.e., Fe(III), SO4(2-), or HCO3-} . Under all conditions tested, the bromophenol isomers were utilized without a lengthy lag period whereas the bromobenzoate isomers were utilized only after a lag period of 23 to 64 days . 2-Bromophenol was debrominated to phenol, with the subsequent utilization of phenol under all three reducing conditions . Debromination of 3-bromophenol and 4-bromophenol was also observed under sulfidogenic and methanogenic conditions but not under iron-reducing conditions . In the bromobenzoate-degrading cultures, no intermediates were observed under any of the conditions tested . Debromination rates were higher under methanogenic conditions than under sulfate-reducing or iron-reducing conditions . The stoichiometric reduction of sulfate or Fe(III) and the utilization of bromophenols and phenol indicated that biodegradation was coupled to sulfate or iron reduction, respectively . The production of phenol as a transient intermediate demonstrates that reductive dehalogenation is the initial step in the biodegradation of bromophenols under iron- and sulfate-reducing conditions.

Ann N Y Acad Sci, 1997 Nov 21, 829, 313 - 25
Bioventing pilot test results at the low point drain area, Offutt AFB, Nebraska; Werner FT et al.; The purpose of this paper was to describe the application of bioventing technology at the LPD site at Offutt AFB, Nebraska and present the results of the 15-month pilot test . The preliminary tests indicated sufficient hydrocarbon contamination was present with the necessary soil characteristics to warrant an extended bioventing pilot test . The six month in situ respiration test indicated that progress was being made in reducing the TVH concentrations and biological activity was still occurring . Laboratory analysis of the final soil samples confirmed the reduction in TRPH and BTEX concentrations indicating that the site is close to complete remediation . However, owing to reduced air flow at greater distances from the VW, more biodegradation is still needed near MPB . The reduced biodegradation at MPB could also be due to the high water tables resulting from heavy rains during the summer and fall of 1993 . The local water table was above the VW and MP screens for several months . The operation of the blower will continue until the site is completely remediated . The single VW pilot test at the LPD site at Offutt AFB has proven the effectiveness of bioventing in reducing TRPH and BTEX contamination in the subsurface . The installation, operation and maintenance costs were minimal . The effectiveness of this application has resulted in three additional bioventing applications at Offutt AFB including the first, full-scale system located in the state of Nebraska.

Appl Environ Microbiol, 1997 Dec, 63(12), 4759 - 64
Carboxylation as an initial reaction in the anaerobic metabolism of naphthalene and phenanthrene by sulfidogenic consortia; Zhang X et al.; The anaerobic biodegradation of naphthalene (NAP) and phenanthrene (PHE) was investigated by using sediment collected from the Arthur Kill in New York/New Jersey harbor . The initial cultures were composed of 10% sediment and 90% mineral medium containing 20 mM sulfate . Complete loss of NAP and PHE (150 to 200 muM) was observed after 150 days of incubation . Upon refeeding, NAP and PHE were utilized within 14 days . The utilization of both compounds was inhibited in the presence of 20 mM molybdate . {14C}NAP and {14C}PHE were mineralized to 14CO2 . The activities could be maintained and propagated by subculturing in mineral medium . In the presence of halogenated analogs, 2-naphthoate was detected in NAP-utilizing enrichments . The mass spectrum of the derivatized 2-napththoate from the enrichment supplemented with both {13C}bicarbonate and NAP indicates the incorporation of 13CO2 into NAP . In the PHE-utilizing enrichment, a metabolite was detected by both high-pressure liquid chromatography and gas chromatography-mass spectrometry analyses . The molecular ion and fragmentation pattern of its mass spectrum indicate that it was phenanthrenecarboxylic acid . The results obtained with {13C} bicarbonate indicate that 13CO2 was incorporated into PHE . It appears, therefore, that carboxylation is an initial key reaction for the anaerobic metabolism and NAP and PHE . To our knowledge, this is the first report providing evidence for intermediates of PAH degradation under anaerobic conditions.

Arch Environ Contam Toxicol, 1998 Feb, 34(2), 188 - 96
Preliminary observations on responses of embryonic and larval Pacific herring, Clupea pallasi, to neutral fraction biodegradation products of weathered Alaska North Slope oil; Middaugh DP et al.; Weathered Alaska North Slope crude oil (ANS 521) was subjected to biodegradation in vigorously stirred incubations for 14 days at 15 +/- 1 degrees C in 20/1000 salinity sterilized seawater, amended with nutrients and inoculated with a hydrocarbon-degrading microorganism (EI2V) isolated from an oil-contaminated beach in Prince William Sound, Alaska . A total of 13.7 mg/L water-soluble neutral fraction (WSF) was recovered from the incubation of weathered ANS 521 . Toxicity/ teratogenicity tests were conducted with WSF recovered from the biodegradation system using embryonic and larval Pacific herring, Clupea pallasi . Exposures were begun at 4, 48, and 96 h postfertilization of herring eggs . Exposure concentrations were 1, 10, and 100% of the original concentration of WSF recovered from incubations (redissolved in 20/1000 salinity sterile seawater at 15 +/- 1 degrees C) . Sterile 20/1000 salinity seawater without the addition of redissolved neutral fraction was used as a control . Significant (p < or = 0.05) embryo mortality or teratogenic responses were observed at WSF concentrations of 10 and 100% . On days 5 through 8 of embryogenesis, counts of heart contraction rates were significantly lower (p < or = 0.05) at the 100% WSF concentration for embryos exposed beginning at 4 and 48 h postfertilization . Grow-out of larvae from selected exposures was conducted . High mortality was noted in larvae exposed to the 10% WSF concentration beginning at 4 and 48 h postfertilization . Most of these larvae died 5 to 8 days after hatching when they elicited vertebral displacements at a time concurrent with the onset of feeding behavior.

J Biomed Mater Res, 1998 Mar 5, 39(3), 446 - 52
Heparin immobilized on proteins usable for arterial prosthesis coating: growth inhibition of smooth-muscle cells; Laemmel E et al.; Gelatin or a mixture of albumin and gelatin has been proposed for the coating of vascular grafts according to their surface thrombogenicity and biocompatibility, and the possibility of biodegradation . Heparin treatment of hemocompatible surfaces improved the patency of prostheses . In this study, different amounts of heparin were immobilized on these protein gels using a water-soluble carbodiimide {1-ethyl-3-(3-dimethylaminopropyl) carbodiimide} . The results showed a coupling of heparin with gelatin and/or albumin at the surface of the gels, stable for as long as 1 month . From 0.20 to 3.60 microg x cm(-2), heparin could be immobilized . The antiproliferative activity of immobilized heparin was controlled toward bovine smooth-muscle cells grown on these gels . Cell growth inhibition was dose dependent, but the percentages of inhibition were lower at day 8 than at day 4 at any heparin concentration used under experimental conditions . Referring to heparin in solution, immobilized heparin displayed an antiproliferative activity that improved the potential interest for coating.

Chem Biol, 1994 Nov, 1(3), 173 - 83
Magnetic circular dichroism studies of exogenous ligand and substrate binding to the non-heme ferrous active site in phthalate dioxygenase; Pavel EG et al.; BACKGROUND: Mononuclear non-heme iron centers are found in the active sites of a variety of enzymes that require molecular oxygen for catalysis . The mononuclear non-heme iron is believed to be the active site for catalysis, and is presumed to bind and activate molecular oxygen . The mechanism of this reaction is not understood . Phthalate dioxygenase is one such enzyme . Because it also contains a second iron site, the Rieske site, it is difficult to obtain information on the structure of the active site . We therefore used magnetic circular dichroism (MCD) spectroscopy to probe the mononuclear, non-heme Fe2+ site in this biodegradative enzyme . RESULTS: The MCD spectrum of the resting enzyme shows features indicative of one six-coordinate Fe2+ site; substrate binding converts the site to two different five-coordinate species, opening up a coordination position for O2 binding . MCD spectra of the corresponding apoenzyme have been subtracted to account for temperature-independent contributions from the Rieske site . Azide binds both to the resting enzyme to produce a new six-coordinate species, showing that one of the ferrous ligands is exchangeable, and also to the enzyme-substrate complex to form a ternary species . The low azide binding constant for the substrate-enzyme species relative to the resting enzyme indicates steric interaction and close proximity between exogenous ligand and the substrate . CONCLUSIONS: We have been able to provide some detailed structural insight into exogenous ligand and substrate binding to the non-heme Fe2+ site, even in the presence of the enzyme's {2Fe-2S} Rieske center . Further mechanistic studies are now required to maximize the molecular-level detail available from these spectroscopic studies.

Polim Med, 1997, 27(1-2), 17 - 37
{Changes in the level of selected laboratory parameters in blood after implantation of chitosan fibers}; Szymonowicz M et al.; The tests were carried out on rats of the Wistar tribe to the peritoneal cavity of which chitosan fibres were implanted . The blood for the tests was taken in 3, 7, 14, 30 and 60 days after the implantation . In the blood hematological, biochemical and clotting system parameters were marked . Moreover they made pathomorphological tests of the tissues surrounding the implanted material and laboratory and biological tests of aqueous extracts from chitosan fibres . The shown quantitative changes in the level of the marked parameters of blood to the 14th day of observation are connected mainly with toxicity of chitosan fibres, whereas to the 30th and 60th day-with the process of biodegradation and resorption of collagenous fibres.

Biomaterials, 1997 Nov, 18(21), 1387 - 409
In-vivo degradation of polyurethanes: transmission-FTIR microscopic characterization of polyurethanes sectioned by cryomicrotomy; McCarthy SJ et al.; A combination of cryomicrotomy and transmission Fourier transform infrared (FTIR) microscopy was used to investigate chemical changes in unstrained sheets of Pellethane 2363-80A, Tecoflex EG80A and Biomer caused by biodegradation (18 month subcutaneous ovine implant) . Cryomicrotomy was used to obtain thin sections (ca . 2.5 microm) from the surface into the bulk, parallel to the plane of the surface . FTIR microscopy was then used to obtain infrared absorbance spectra in the range 4000-600 cm(-1) . Comparisons between the infrared spectra (by spectral subtraction) from implant surface, implant interior and non-implanted controls were used to detect chemical changes . Scanning electron microscopy was used to assess microstructural changes owing to biodegradation . Biodegradation in Biomer was observed as uniform pitting and superficial fissuring (<2.0 microm depth) over the implant surface . Biodegradation in Pellethane 2363-80A and Tecoflex EG 80A was observed as severe localized embrittlement of the surface with fissures infiltrating up to 40 microm into the bulk . The chemical changes associated with biodegradation were observed as localized oxidation of the soft segment and hydrolysis of the urethane bonds joining hard and soft segments . Tecoflex EG80A was also found to be susceptible to localized hydrolysis of the urethane bond within the aliphatic hard segment . Biomer showed evidence of a significant non-specific degradation in the non-implanted wet control (37 degrees C phosphate buffered saline at pH 7.3) samples and in the implant bulk.

J Biomed Mater Res, 1998 Feb, 39(2), 184 - 9
Identification and quantification of the crystalline structures of poly(vinylidene fluoride) sutures by wide-angle X-ray scattering and differential scanning calorimetry; Laroche G et al.; The outstanding biocompatibility of the polyvinylidene fluoride (PVDF) monofilament suture together with other desirable characteristics, such as ease of handling and resistance to biodegradation, makes it an attractive alternative monofilament suture material for cardiovascular surgery . However, to achieve a high performance suture, the polymeric raw material must be exposed to different treatments, which lead to different degrees and types of crystallization . Since these crystalline modifications deeply influence the mechanical characteristics and the biostability of the sutures, the authors hereby propose a method of quantifying the different structures of PVDF using wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) . The commercial devices are achieved by coloring and processing the polymeric raw material . The white and unprocessed 4-0 unswaged suture presents 19% of the alpha phase, 38% of the beta structure, and no gamma form . Coloration increases the amount of the beta phase by 5-9% at the expense of the alpha phase . On the other hand, processing the fibers lead to the conversion of some of the amorphous phase to the gamma structure, the importance of which is 6-7% . Finally, tensile measurements performed on the different PVDF fibers clearly proves that their mechanical characteristics depend on the presence of these crystalline forms in the polymeric structure of PVDF.

Pharm Res, 1997 Dec, 14(12), 1744 - 9
Prednicarbate versus conventional topical glucocorticoids: pharmacodynamic characterization in vitro; Lange K et al.; PURPOSE: Pharmacodynamic characterization of topical glucocorticoids as prednicarbate (PC), its metabolites prednisolone 17-ethylcarbonate (PEC) and prednisolone (PD), betamethasone 17-valerate (BMV), betamethasone (BM) and desoximetasone (DM) by evaluating their effects on epidermal and dermal cells . Synopsis of pharmacokinetic and pharmacodynamic studies, possibly explaining the improved benefit-risk ratio of prednicarbate . METHODS: Isolated foreskin keratinocytes were used to investigate the influence on epidermal inflammatory processes, dermal fibroblasts of the same origin to study antiproliferative activities of glucocorticoids . Interleukins were measured by ELISA-assay, the influence on II-1 alpha-production also on mRNA-level by RNAse protection assay . Proliferation was assessed by 3H thymidine incorporation and biodegradation by HPLC/UV-absorption . Cell viability was controlled by MTT assay . RESULTS: In keratinocytes, inflammation was induced by TNF alpha, resulting in an increased II-1 alpha synthesis . This cytokine was particularly suppressed by PC and BMV, whereas PEC, PD, DM and BM were less potent (p < or = 0.05) . Since, however, the double ester PC is rapidly degraded in keratinocytes, a RNAse-protection assay of II-1 alpha mRNA was performed allowing short incubation times and thus minimizing biodegradation effects . In agreement with the previous experiment, the antiinflammatory potency of native PC was confirmed . In fibroblasts, II-1 alpha and II-6 synthesis indicate proliferation and inflammation respectively . Whereas PC inhibited II-1 alpha and II-6 production in fibroblasts to a minor extent only, it was strongly reduced by the conventional glucocorticoids and PEC (p < or = 0.05) . The minor unwanted effect of PC on fibroblasts was also reflected by its low influence on cell proliferation as assayed by 3H thymidine incorporation . More pronounced antiproliferative features were observed with BM, PEC and especially BMV . CONCLUSIONS: Correlating antiphlogistic effects in keratinocytes (suppression of II-1 alpha) with antiproliferative effects in fibroblasts (suppression of II-1 alpha and II-6), the improved benefit-risk ratio of PC compared to conventional glucocorticoids does not result only from distinct drug metabolism in the skin but also from a specific influence on the cytokine network.

J Ind Microbiol Biotechnol, 1997 Nov-Dec, 19(5-6), 350 - 4
Biocatalysis, biodegradation and bioinformatics; Wackett LP; Biocatalysis, biodegradation and bioinformatics are prominent scientific fields in industrial microbiology and biotechnology . This paper describes developments in these fields with a focus on the role of David T Gibson as a researcher and mentor . He has pioneered studies on the mechanisms by which aerobic microorganisms transform aromatic hydrocarbons . In addition, his research has served as a model for further investigations into bacterial atrazine and dichloromethane catabolism described here . Microbial catabolism research requires information on organic chemistry, microorganisms, metabolic pathways, catabolic genes, and enzymes . These information needs are now being met more comprehensively by development of the University of Minnesota Biocatalysis/Biodegradation Database.

Folia Microbiol (Praha), 1997, 42(5), 517 - 20
Identification of alkylpolyoxyethylene glycols in the residues after biodegradation of their mixtures by CGC and previous derivatization; Richter P et al.; This study deals with the identification of individual n-alkylpolyoxyethylene glycols among the products of oxyethylenation of n-nonyl- and n-decylalcohol and with the identification of these compounds in the reaction mixture after their biodegradation . The individual glycols were identified by their retention indices for the column temperature programmed linearly, by the correlation of the retention indices with the number of oxyethylene groups in the molecule and by increments of retention indices for the incoming oxyethylene group or methylene group . The biodegradation process of oxyethylenation products of reaction of one mole of n-nonylalcohol and n-decylalcohol, respectively, with three moles of ethylene oxide was studied . n-Alkylpolyoxyethylene glycols in oxyethylenation products or their residues isolated from the aqueous solution after their biodegradation processes were derivatized into acetates, trifluoroacetates and trimethylsilyl derivatives before carrying out their identification and determination.

Folia Microbiol (Praha), 1997, 42(5), 513 - 6
Use of mineral nutrients and surface-active substances in a biodegradation process modulation; Cejkova A et al.; The capability of a bacterial population to degrade oil hydrocarbons and naphthalene was found to be markedly enhanced by an optimized P:N ratio as well as by proper application of a surface-active compound . The importance of this optimization procedure was shown by both laboratory and technologically performed experiments.

Appl Environ Microbiol, 1998 Jan, 64(1), 153 - 8
Morpholine degradation pathway of Mycobacterium aurum MO1: direct evidence of intermediates by in situ 1H nuclear magnetic resonance; Combourieu B et al.; Resting Mycobacterium aurum MO1 cells were incubated with morpholine, a waste from the chemical industry . The kinetics of biodegradation was monitored by using in situ nuclear magnetic resonance (NMR) . The incubation medium was directly analyzed by 1H NMR . This technique allowed the unambiguous identification of two intermediates of the metabolic pathway involved in the biodegradation process, glycolate and 2-(2-aminoethoxy)acetate . The latter compound, which was not commercially available, was synthesized, in three steps, from 2-(2-aminoethoxy)ethanol . Quantitative analysis of the kinetics of degradation of morpholine was performed by integrating the signals of the different metabolites in 1H-NMR spectra . Morpholine was degraded within 10 h . The intermediates increased during the first 10 h and finally disappeared after 20 h incubation . Assays of degradation were also carried out with glycolate and ethanolamine, hypothetical intermediates of the morpholine degradation pathway . They were degraded within 4 and 8 h, respectively . Until now, no tool for direct detection of intermediates or even morpholine has been available, consequently, only hypothetical pathways have been proposed . The approach described here gives both qualitative and quantitative information about the metabolic routes used in morpholine degradation by M . aurum MO1 . It could be used to investigate many biodegradative processes.

Chemosphere, 1997 Dec, 35(12), 2953 - 72
Testing biodegradability with standardized methods; Pagga U; Laboratory test methods are used by industry laboratories to determine biodegradability, an important parameter for the evaluation of the ecological behaviour of substances . Biodegradability has a key role due to the simple fact that a degradable substance will cause no long term risk in the environment . The great variety of biodegradation processes in the natural environment and in technical plants for treating waste water and solid wastes gave rise to a rather large number of test methods based on different test principles . To guarantee the acceptance of the test results by authorities and customers internationally standardized methods (ISO, OECD) and established quality criteria (GLP, EN 45,000, ISO 9000) are used.

Chemosphere, 1997 Dec, 35(12), 2807 - 15
Biodegradation of benzene, toluene, and other aromatic compounds by Pseudmonas sp . D8; Chang BV et al.; Pseudomonas sp . D8 strain, which has the potential to utilize toluene as a sole carbon source, was isolated . At a concentration of 100 mg/l, this strain was found to efficiently degrade toluene and benzene (both individually and in mixture) in culture medium at 30 degrees C and pH7 . Following a two-hour lag phase, complete biodegradation of 100 mg/l toluene or benzene occurred within 6 to 8 hours . The addition of nitrate, phosphate, or sulfate at various concentrations were found to have significant influence on both toluene and benzene degradation . In addition, results show that the D8 strain has the ability to degrade monochlorophenols, nitrophenols, and phenol, but not aliphatic compounds . Inoculation of groundwater samples containing 100 mg/l toluene or benzene with Pseudmonas sp . D8 resulted in rapid degradation within 24-33 hours.

J Biomater Sci Polym Ed, 1997, 8(12), 905 - 17
Synthesis, characterization, biodegradation, and drug delivery application of biodegradable lactic/glycolic acid oligomers: I . Synthesis and characterization; Wang N et al.; A series of oligomers or low molecular weight polymers of lactic and/or glycolic acid has been synthesized with different molar ratios of lactic to glycolic acid . These oligomers have been characterized with respect to oligomer composition, molecular weight, intrinsic viscosity, crystallinity, melting temperature, and glass transition temperature . The polymerization conditions for the lactic/glycolic acid oligomer syntheses were as follows: 180-220 degrees C, 5 mm Hg, 5 h, and 0.1 wt% of catalyst (antimony oxide) concentration . The polymeric compositions correlated to the feed ratios of lactic to glycolic acid . The molecular weight of the oligomers ranged from 895.8 +/- 48.7 to 1368.0 +/- 0 D with the intrinsic viscosity ranging from 0.0513 to 0.0814 dl g-1 . The lactic/glycolic acid oligomers were found to be amorphous . The glass transition temperatures of the lactic/glycolic acid oligomers were lower than physiological temperature.

Appl Microbiol Biotechnol, 1997 Oct, 48(4), 549 - 52
The ability of soil-borne fungi to degrade organophosphonate carbon-to-phosphorus bonds; Krzysko-Lupicka T et al.; The ability of a wide variety of soil-borne fungal strains to degrade four structurally different compounds containing P-C bonds, namely the naturally occurring amino acid ciliatine, the popular herbicide glyphosate, phosphonoacetic acid and 2-amino-3-phosphonopropionic acid, was studied in order to show that soil fungi may play an important role in the biodegradation of organophosphonates . Most of the strains appeared to utilize ciliatine as the sole source of phosphorus for growth . Only a limited number of strains were able to grow on the other phosphonates used in this work . The strains of Trichoderma harzianum, Scopulariopsis sp . and Aspergillus niger chosen for more detailed study show the ability to degrade ciliatine, glyphosate and also amino(3-methoxyphenyl)methylphosphonic acid effectively.

Microbiology, 1997 Nov, 143 ( Pt 11), 3649 - 59
Re-evaluation of the hypothesis that biodegradable surfactants stimulate surface attachment of competent bacteria; Owen SA et al.; The hypothesis that biodegradable surfactants stimulate the attachment of biodegradation-competent bacteria to surfaces has been re-evaluated using a variant of the surfactant-degrading bacterium Pseudomonas sp . DES1 designated Pseudomonas sp . DES2 . This variant was identical to the parental strain in terms of its carbon-utilization patterns and alcohol dehydrogenase and alkylsulfatase complements (enzymes involved in surfactant biodegradation), but differed markedly in its growth characteristics when using sodium dodecyl triethoxysulfate or triethylene glycol dodecyl ether as secondary carbon sources . Pseudomonas sp . DES1 exhibited diauxie in these surfactant-based culture media in contrast to Pseudomonas sp . DES2, which exhibited single-phase growth . Pseudomonas sp . DES2 did not attach to river sediment in a microcosm system when challenged with a dose of either surfactant, although it did biodegrade the substrate . In contrast, Pseudomonas sp . DES1 attached to the river sediment whilst biodegrading the test substrate . It is concluded that the ether-scission system, which is responsible for primary biodegradation of both substrates, is deregulated in Pseudomonas sp . DES2 in contrast to that in Pseudomonas sp . DES1, and that, contrary, to a previous hypothesis, biodegradable surfactants do not necessarily stimulate the attachment of biodegradation-competent bacteria during their biodegradation.

J Chromatogr B Biomed Sci Appl, 1997 Sep 26, 698(1-2), 69 - 80
High-performance liquid chromatographic separation and tandem mass spectrometric identification of breakdown products associated with the biological hydrolysis of a biomedical polyurethane; Wang GB et al.; As part of ongoing investigations into the biological degradation of biomaterials, methods have been developed to isolate and chemically analyze polymer biodegradation products . The use of these methods can provide information on the biodegradation product profiles and yield concentration levels for the isolated products . The latter information is required to assess the toxicological nature of biomaterials and their related degradation products . In this study a model biomedical polyurethane was synthesized with toluene diisocyanate, polyester diol and ethylene diamine, and then incubated at 37 degrees C in a biological solution containing enzyme . The biodegradation products were isolated from the in vitro system and prepared for HPLC analysis, by using a combination of ultrafiltration, freeze drying and liquid-solid extraction . The ultrafiltration and the liquid-solid extraction effectively removed protein contamination . The separation of more than 20 degradation products, with gradient HPLC, was optimized using a photodiode array detector . The separated degradation products were identified using a tandem mass spectrometer . The model polyurethane was labeled with 14C in different segments, in order to assist in confirming the efficiency of the sample preparation and isolation methods . A detection limit of 2 ng was found . No toluene diamine - a suspected human carcinogen associated with some medical implants - could be found in the test samples . This represents a significant finding since the amount of this injected sample actually contained a total of 28 microg of degradation products isolated from the incubation medium.

J Air Waste Manag Assoc, 1997 Oct, 47(10), 1041 - 50
Development and analysis of oxygen-sensing probes for in situ monitoring of unsaturated solid-state biodegradation processes; VanderGheynst JS et al.; Oxygen (O2) sensors have been developed for in situ measurement of O2 in high-solids degradation processes . The O2 sensor has been shown to withstand the corrosive environment of the biodegradation process with high humidity and temperatures exceeding 60 degrees C . Calibration tests prior to and after in situ operation showed the sensor to perform accurately and reproducibly after 71 days of in situ operation . A linear relationship between O2-sensor output and water vapor pressure was confirmed through calibration experiments . To compensate for the effect of water vapor pressure on O2-sensor measurements, O2 concentration was expressed on a dry air basis using the confirmed linear relationship . In situ O2-sensor output expressed on a dry air basis was found to follow trends of gas samples analyzed by gas chromatography with good agreement.

Chemosphere, 1997 Oct, 35(8), 1773 - 9
A note on the use of the CEC L-33-A-93 test to predict the potential biodegradation of mineral oil based lubricants in soil; Battersby NS et al.; The biodegradabilities of five unformulated mineral oils (brightstock, 150 SN base oil, white oil and two gas oils) were determined in the CEC L-33-A-93 test and during 20 weeks incubation in nutrient-supplemented soil microcosms . Biodegradation in both studies was measured as the loss of extractable hydrocarbon ('primary' biodegradation) . There was a statistically significant (P < 0.01) rectilinear relationship between the extents of biodegradation in both test systems . The results indicate that the CEC method could be used as a relatively simple, quick and inexpensive test for assessing the potential biodegradation of mineral oil based lubricants in soil.

Arch Environ Contam Toxicol, 1997 Oct, 33(3), 247 - 51
Isoxaben soil biodegradation in pear tree orchard after repeated high dose application; Rouchaud J et al.; During the past nine years, each of the plots of a pear tree orchard were treated annually with the same herbicide treatment . The following herbicide treatments were compared, each being made by application of a mixture of two or three herbicides: 1a, no herbicide at all, weeds being hoed (control 1a); 2, diuron + paraquat 3 + 1 kg/ha; 3, simazine + paraquat 2 + 1 kg/ha; 4, isoxaben + diuron + paraquat 0.5 + 1.6 + 1 kg/ha; and 5, isoxaben + simazine + paraquat 0.5 + 1.25 + 1 kg/ha . In March 1996, one year after the final orchard herbicide treatment, isoxaben could not be detected in the soils of any field plots; isoxaben was incorporated at 0.74 mg/kg in the loamy soils sampled separately in each of the field plots, and the soils were incubated in the laboratory . Isoxaben soil half-lives were 92 days in the soils treated previously with herbicide treatments 1a, 2, or 3 and 42 days in the soils treated with herbicide treatments 4 and 5 . The repeated isoxaben treatments applied in the past thus enhanced the isoxaben soil biodegradation; diuron, simazine, and paraquat had no influence on this rate enhancement . On the other hand, herbicide treatments 4 and 5 were applied in the orchard in April 1996 on the corresponding plots treated in this manner for the last nine years . Isoxaben + paraquat 0.5 + 1 kg/ha was applied simultaneously on other plots (control 1b) not treated in the past with isoxaben . During the growth season in the orchard, the isoxaben soil half-lives in the control plots 1b was 101 days, and 41 days in the plots where herbicide treatments 4 or 5 were applied.

FEMS Microbiol Lett, 1997 Oct 15, 155(2), 155 - 9
The biodegradation of tributyl phosphate by naturally occurring microbial isolates; Thomas RA et al.; The biodegradation of tributyl phosphate by a mixed culture of Pseudomonads was demonstrated . Growth and the rate of tributyl phosphate consumption were variable and divisible into rapid and slow rates . Rapidly growing, rapidly tributyl phosphate-utilising cultures contained a 22-24 kb DNA fragment isolated by two methods, which was not visible in the cultures growing slowly . The mixed culture gave five periods of rapid growth interspersed with periods of poor growth during 7 months of weekly subculture, with the 22-24 kb DNA fragment detectable during the rapidly growing periods only . Seven Pseudomonads isolated from the culture grew at the expense of tributyl phosphate as the sole phosphorus source but spontaneously and irreversibly lost this ability after eight serial subcultures.

Adv Microb Physiol, 1998, 39, 339 - 77
Biodegradation and metabolism of unusual carbon compounds by anoxygenic phototrophic bacteria; Sasikala C et al.; Anoxygenic phototrophic bacteria play an important role in anaerobic nutritional cycles . The most readily used and widely studied carbon sources for growth of these bacteria are organic acids and a few carbohydrates . In this review we survey the growing knowledge on the metabolism of a number of other carbon sources, particularly polymers (starch, poly(3-hydroxyalkanoates)), aromatic compounds (natural and xenobiotic), one-carbon compounds, alcohols, aliphatic hydrocarbons and higher fatty acids, and their influence on various cellular activities of purple non-sulfur bacteria . We also discuss the possible exploitations in various biotechnological processes of this group of microorganisms while metabolizing unusual carbon compounds.

Annu Rev Microbiol, 1997, 51, 375 - 414
Sulfur tuft and turkey tail: biosynthesis and biodegradation of organohalogens by Basidiomycetes; de Jong E et al.; Chlorinated aliphatic and aromatic compounds are generally considered to be undesirable xenobiotic pollutants . However, the higher fungi, Basidiomycetes, have a widespread capacity for organohalogen biosynthesis . Adsorbable organic halogens (AOX) and/or low-molecular-weight halogenated compounds are produced by Basidiomycetes of 68 genera from 20 different families . Most of the 81 halogenated metabolites identified from Basidiomycetes to date are chlorinated, although brominated and iodated metabolites have also been described . Two broad categories of Basidiomycete organohalogen metabolites are the halogenated aromatic compounds and the haloaliphatic compounds . Some of these organohalogen metabolites have demonstrable physiological roles as antibiotics and as metabolites involved in lignin degradation . Basidiomycetes produce large amounts of low-molecular-weight organohalogens or adsorbable organic halogens (AOX) when grown on lignocellulosic substrates . In our view, Basidiomycetes, as decomposers of forest litter, are a major source of natural organohalogens in terrestrial environments . Basidiomycetes are also potent degraders of a wide range of chlorinated pollutants, such as bleachery effluent from kraft mills and pentachlorophenol, polychlorinated dioxins, and polychlorinated biphenyls . The extracellular, lignin-degrading enzymes of the Basidiomycetes are involved in the oxidative degradation of chlorophenols and dioxin and can cause reductive dechlorination of halomethanes . There is no clear-cut separation between "polluters" and "clean-uppers" within the Basidiomycetes . Several genera, e.g . Bjerkandera, Hericium, Phlebia, and Trametes, produce significant amounts of chlorinated compounds but are also highly effective in metabolizing or biotransforming chlorinated pollutants.

Nat Biotechnol, 1997 Oct, 15(10), 984 - 7
Biodegradation of organophosphorus pesticides by surface-expressed organophosphorus hydrolase; Richins RD et al.; Organophosphorus hydrolase (OPH) was displayed and anchored onto the surface of Escherichia coli using an Lpp-OmpA fusion system . Production of the fusion proteins in membrane fractions was verified by immunoblotting with OmpA antisera . Inclusion of the organophosphorus hydrolase signal sequence was necessary for achieving enzymatic activity on the surface . More than 80% of the OPH activity was located on the cell surface as determined by protease accessibility experiments . Whole cells expressing OPH on the cell surface degraded parathion and paraoxon very effectively without any diffusional limitation, resulting in sevenfold higher rates of parathion degradation compared with whole cells with similar levels of intracellular OPH . Immobilization of these live biocatalysts onto solid supports could provide an attractive means for pesticide detoxification in place of immobilized enzymes, affording a reduced diffusional barrier.

Gene, 1997 Sep 1, 196(1-2), 113 - 9
Cloning and sequence analysis of two laccase complementary DNAs from the ligninolytic basidiomycete Trametes versicolor; Ong E et al.; Laccases are oxidoreductase enzymes involved in the oxidation of various phenolic compounds . They may play a role in the biodegradation of lignin and in the dechlorination of chlorophenols . The cDNAs encoding laccase LccI and a putative laccase LccIV and the gene for LccI from the white-rot basidiomycete Trametes versicolor were cloned, sequenced and characterized . The genomic DNA of lccI consists of 2128 bp, with the coding region interrupted by 10 introns; the cDNA consists of a 1560 bp open reading frame (ORF) . The cDNA of the putative lccIV gene consists of a 1581 bp ORF, with a 794 bp 5' untranslated region . The size of the major transcript for both lccI and lccIV is approximately 2.3 kb . Transcription of lccIV was induced by 2,5-dimethylaniline, whereas the opposite effect was observed for lccI . Laccases I and IV contain highly conserved histidinyl and cysteinyl residues, believed to be involved in binding copper, and share extensive sequence similarity with other laccases produced by both ligninolytic and non-ligninolytic fungi.

Anesthesiology, 1997 Sep, 87(3), 517 - 26
Recovery and kinetic characteristics of desflurane and sevoflurane in volunteers after 8-h exposure, including kinetics of degradation products; Eger EI 2nd et al.; BACKGROUND: Desflurane and sevoflurane permit speedier changes in anesthetic partial pressures than do older halogenated anesthetics . The authors determined the kinetic characteristics of desflurane and sevoflurane and those of compound A {CH2F-O-C(=CF2)(CF3)}, a nephrotoxic degradation product of sevoflurane . METHODS: Volunteers received 1.25 minimum alveolar concentration of desflurane or sevoflurane, each administered for 8 h in a fresh gas inflow of 2 l/min . Inspired (F(I)) and end-tidal (F(A)) concentrations of anesthetic and compound A were measured during administration, and F(A) relative to F(A0) (the last end-tidal concentration during administration) during elimination . The indices of recovery were also measured . RESULTS: The ratio F(I)/F(A) rapidly approached 1.0, with values greater for sevoflurane (desflurane 1.06 +/- 0.01 vs . sevoflurane 1.11 +/- 0.02, mean +/- SD) . The ratio F(A)/F(I) for compound A was approximately 0.8 . The F(A)/F(A0) ratio decreased slightly more rapidly with desflurane than with sevoflurane, and objective measures indicated faster recovery with desflurane: The initial response to command (14 +/- 4 min vs . 28 +/- 8 min {means +/- SD}) and orientation (19 +/- 4 vs . 33 +/- 9 min) was quicker, and recovery was faster as defined by results of the Digit Symbol Substitution, P-deletion, and Trieger tests . Desflurane produced less vomiting (1 {0.5, 3}; median {quartiles} episodes) than did sevoflurane (5 {2.5, 7.5} episodes) . The F(A)/F(A0) ratio for compound A decreased within 5 min to a constant value of 0.1 . CONCLUSIONS: These anesthetics have kinetics consistent with their solubilities . Sevoflurane's greater biodegradation probably increases F(I)/F(A) differences during anesthetic administration and decreases F(A)/F(A0) differences during elimination . The F(A) for compound A differs from F(I) by 20% (F(A)/F(I) = 0.8) because of substantial degradation . Recovery from anesthesia proceeds nearly twice as fast with desflurane than with sevoflurane . Differences in ventilation, or alveolar or tissue elimination, do not completely explain the slower recovery with sevoflurane.

Appl Microbiol Biotechnol, 1997 Aug, 48(2), 275 - 9
Microbial degradation of tetraethyl lead in soil monitored by microcalorimetry; Teeling H et al.; Sieved agricultural soil samples were treated with the anti-knock agent tetraethyl lead (Et4Pb), and the resulting effects were analyzed by microcalorimetry . Et4Pb additions resulted in an increase of the heat production rate, provided that oxygen was present and that the soil was not autoclaved . The increased heat production rate was accompanied by degradation of Et4Pb, as verified by speciation analysis (GC-MS) of the remaining Et4Pb and its ionic degradation products (triethyl lead and diethyl lead cations) . Conclusive evidence was obtained that these transformations were mediated mainly by microbes . At an initial Et4Pb concentration of 2 g Pb/kg dry weight the biodegradation rate was about 780 mumol day-1 kg dry weight-1, whilst the chemical decomposition was only 50 mumol day-1 kg dry weight-1 . A fivefold rise of the initial Et4Pb concentration resulted in a decrease of the biodegradation rate to 600 mumol day-1 kg dry weight-1 and an increase of the chemical decomposition to 200 mumol day-1 kg dry weight-1 . The biodegradation rate was not influenced by the addition of glucose, which means that no indication for a co-metabolic attack of Et4Pb was found.

FEMS Microbiol Rev, 1997 Jul, 20(3-4), 261 - 75
Protistan communities in aquifers: a review; Novarino G et al.; Eukaryotic microorganisms (protists) are a very important component of microbial communities inhabiting groundwater aquifers . This is not unexpected when one considers that many protists feed heterotrophically, by means of either phagotrophy (bacterivory) or osmotrophy . Protistan numbers are usually low (< 10(2) per g dw of aquifer material) in pristine, uncontaminated aquifers but may increase by several orders of magnitude in aquifers subject to organic pollution . Small flagellates (typically 2-3(5) microns in size in situ) are by far the dominant protists in aquifers, although amoebae and occasionally ciliates may also be present in much lower numbers . Although a wealth of new taxonomic information is waiting to be brought to light, interest in the identity of aquifer protists is not exclusively academic . If verified, the following hypotheses may prove to be important towards our understanding of the functioning of microbial communities in aquifers: (1) Differences in swimming behavior between species of flagellates lead to feeding heterogeneity and niche differentiation, implying that bacterivorous flagellates graze on different subsets of the bacterial community, and therefore play different roles in controlling bacterial densities . (2) Bacterivorous flagellates grazing on bacteria capable of degrading organic compounds have an indirect effect on the overall rates of biodegradation.

Chemosphere, 1997 Sep, 35(5), 1143 - 60
Seasonal temperature declines do not decrease periphytic surfactant biodegradation or increase algal species sensitivity; Lee DM et al.; The effects of seasonally decreasing river water temperature on surfactant biodegradation and algal sensitivity are reviewed from four stream mesocosm studies conducted over a 5-year period . Seasonal temperatures ranged from 28 to 0 degree C over all studies and temperature declines were approximately 9 to 14 degrees C over the course of each individual study . Mesocosm periphyton were naturally colonized on tile substrata with in-flowing river water for a period of 3 to 8 weeks prior to the initiation of sampling . Streams were dosed for 8 to 11 weeks with microgram/L (ppb) quantities of the surfactants C12-alkyl sulfate (C12-AS), C45E2.17S-alkyl ethoxysulfate (AES), C25E6-alkyl ethoxylate (AE) or 0 to 13% final effluent during the sampling period . Mineralization of C12-AS and AE by periphyton in the dosed streams generally increased over the dosing period while mineralization remained approximately constant in the control streams . The results from the AE study occurred with an increase in periphyton heterotrophic respiration . Mineralization of AES increased over the dosing period in streams receiving the highest dose of AES and remained constant in streams receiving lower doses . All studies involving surfactant exposure demonstrated a positive correlation between surfactant concentration and mineralization during periods of seasonal temperature decline . Mineralization of AE by periphyton dosed with final effluent increased slightly over the testing period . Periphytic algal taxonomy and biovolume were evaluated during the AES study . Overall, these tests showed no increases in species sensitivity over the testing period . Taken collectively, these results indicate that there is no correlation between naturally decreasing seasonal temperatures and lower rates of surfactant mineralization or increased species sensitivity by naturally acclimated periphyton.

J Biomater Sci Polym Ed, 1997, 8(10), 779 - 95
The effect of phospholipids on the biodegradation of polyurethanes by lysosomal enzymes; Labow RS et al.; Although biodegradation of model poly(ester-urethane)s and poly(ether-urethane)s has been demonstrated using a single enzyme system (cholesterol esterase (CE) in vitro, in vivo biodegradation most likely involves many processes acting together . In this study, the physical (film vs textured surface) and chemical (poly(urethane)s containing polycaprolactone (PCL) vs poly(tetramethylene oxide) (PTMO)) nature of the materials as well as the products of enzymatic reactions known to occur during the inflammatory response (CE and phospholipase A2 (PLA)) were assessed for their effects on poly(urethane) (PU) biodegradation in vitro . A mixed micelle (phosphatidylcholine (PC):lysoPC (LPC):oleic acid (OA): 2:1:1) significantly increased the release of radiolabelled products from a C-labelled poly(ester-urethane) (TDI/PCL/ED) caused by CE . This effect was further enhanced when this material was cast as a textured surface . A model poly(ether-urethane) showed no significant enhancement of CE-mediated hydrolysis in the presence of phospholipids and their breakdown products whether cast as a film or a textured surface . PLA caused a small but significant release of radiolabel from TDI/PCL/ED which was enhanced in the presence of its substrate, PC, and a mixture of PC with its breakdown products, LPC and OA . Based on the results of this study, it may be possible to hypothesize that during the inflammatory response when PLA is activated, enhancement of the biodegradation of a PU could occur by direct action of PLA on the poly(ester-urethane) and by stimulation of CE due to the formation of LPC and OA occurring when PLA hydrolyses PC, its natural substrate

Appl Environ Microbiol, 1997 Sep, 63(9), 3719 - 23
Biodegradation of petroleum hydrocarbons by psychrotrophic Pseudomonas strains possessing both alkane (alk) and naphthalene (nah) catabolic pathways; Whyte LG et al.; Three hydrocarbon-degrading psychrotrophic bacteria were isolated from petroleum-contaminated Arctic soils and characterized . Two of the strains, identified as Pseudomonas spp., degraded C5 to C12 n-alkanes, toluene, and naphthalene at both 5 and 25 degrees C and possessed both the alk catabolic pathway for alkane biodegradation and the nah catabolic pathway for polynuclear aromatic hydrocarbon biodegradation . One of these strains contained both a plasmid slightly smaller than the P . oleovorans OCT plasmid, which hybridized to an alkB gene probe, and a NAH plasmid similar to NAH7, demonstrating that both catabolic pathways, located on separate plasmids, can naturally coexist in the same bacterium.

Appl Environ Microbiol, 1997 Sep, 63(9), 3622 - 7
Rhamnolipid (biosurfactant) effects on cell aggregation and biodegradation of residual hexadecane under saturated flow conditions; Herman DC et al.; The objective of this research was to evaluate the effect of low concentrations of a rhamnolipid biosurfactant on the in situ biodegradation of hydrocarbon entrapped in a porous matrix . Experiments were performed with sand-packed columns under saturated flow conditions with hexadecane as a model hydrocarbon . Application of biosurfactant concentrations greater than the CMC (the concentration at which the surfactant molecules spontaneously form micelles or vesicles {0.03 mM}) resulted primarily in the mobilization of hexadecane entrapped within the sand matrix . In contrast, application of biosurfactant concentrations less than the CMC enhanced the in situ mineralization of entrapped hexadecane; however, this effect was dependent on the choice of bacterial isolate . The two Pseudomonas isolates tested, R4 and ATCC 15524, were used because they exhibit different patterns of biodegradation of hexadecane, and they also differed in their physical response to rhamnolipid addition . ATCC 15524 cells formed extensive multicell aggregates in the presence of rhamnolipid while R4 cells were unaffected . This behavior did not affect the ability of the biosurfactant to enhance the biodegradation of hexadecane in well-mixed soil slurry systems but had a large affect on the extent of entrapped hexadecane biodegradation in the sand-packed-column system that was used in this study.

J Biomed Mater Res, 1997 Sep 5, 36(3), 407 - 17
Biodegradation of a poly(ester)urea-urethane by cholesterol esterase: isolation and identification of principal biodegradation products; Wang GB et al.; Synthesized poly(ester)urea-urethanes with 14C-labeled toluene diisocyanate or 14C-labeled chain extender ethylene diamine were incubated with cholesterol esterase in a phosphate buffer solution at 37 degrees C . A number of biodegradation products, generated at the level of 2.8 micrograms/cm2 of polymer surface area, were isolated from this simulated physiologic system . Individual products were obtained by separation with reversed-phase high-performance liquid chromatography . The two different radiolabels were used to assist in the identification of degradation products from hard- and soft-segment domains . Approximately 20 degradation products were isolated; however, toluene diamine (TDA) was not detected from the chromatographic separation . Two principal products were identified by tandem mass spectrometry . Both products are TDA derivatives (secondary aromatic diamine) substituted with end units of the polyester segment at N and N' positions of TDA . The absence of free TDA suggests that there could be a stabilization of urethane and urea linkages within the toluene diisocyanate (TDI) segments of the polyurethanes . For TDI-synthesized polymers, this finding raises awareness to the potential biological importance of degradation products other than TDA, particularly to their interaction with surrounding cells.

J Biomed Mater Res, 1997 Aug, 36(2), 246 - 57
In vivo biocompatibility and biostability of modified polyurethanes; Mathur AB et al.; Modified segmented polyurethanes were examined for biostability and biocompatibility using an in vivo cage implant system for time intervals of 1, 2, 3, 5, and 10 weeks . Two types of materials were used: polyether polyurethanes and polycarbonate polyurethanes . Two unmodified polyether polyurethanes (PEUU A' and SPU-PRM), one PDMS endcapped polyether polyurethane (SPU-S), and two polycarbonate polyurethanes (SPU-PCU and SPU-C) were investigated in this study . Techniques used to characterize untreated materials were dynamic water contact angle, stress-strain analysis, and gel permeation chromatography . Cellular response was measured by exudate analysis and by macrophage and foreign body giant cell (FBGC) densities . Material characterization, postimplantation, was done by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) in order to quantify biodegradation and scanning electron microscopy (SEM) to qualitatively describe the cellular response and biodegradation . The exudate analysis showed that the acute and chronic inflammatory responses for all materials were similar . Lower FBGC densities and cell coverage on SPU-S were attributed to the hydrophobic surface provided by the PDMS endgroups . The polycarbonate polyurethanes did not show any significant differences in cell coverage or FBGC densities even though the macrophage densities were slightly lower compared to polyether polyurethanes . By 10 weeks, biodegradation in the case of PEUU A' and SPU-PRM was extensive as compared to SPU-S because the PDMS endcaps of SPU-S provided a shield against the oxygen radicals secreted by macrophages and FBGCs and lowered the rate of biodegradation . In the case of polycarbonate polyurethanes, the oxidative stability of the carbonate linkage lowered the rate of biodegradation tremendously as compared to the polyether polyurethanes (including SPU-S) . The minor amount of biodegradation seen in polycarbonate polyurethanes at 10 weeks was attributed to hydrolysis of the carbonate linkage.

J Biomed Mater Res, 1997 Aug, 36(2), 223 - 32
The effect of hard segment size on the hydrolytic stability of polyether-urea-urethanes when exposed to cholesterol esterase; Santerre JP et al.; Previous studies have shown that both polyester and polyether-based polyurea-urethanes are susceptible to cleavage by hydrolytic enzymes . Furthermore, it has been hypothesized that the degree of hard segment micro-domain formation in polyurethane materials, as well as its structure, influences the ability of enzymes to degrade the polymers . The current study has investigated a series of segmented polyether-urea-urethanes synthesized with the same reagents but having different hard segment content . Using these materials, the relationship between the formation of hard segment domains and the hydrolysis of urea/urethane groups was specifically addressed . Both differential scanning calorimetry and X-ray photo-electron spectroscopy data indicated that the three materials differed significantly in the extent of hard segment domain formation and the nature of the chemical groups located in the top 10 nm of the surface . Biodegradation studies showed a strong dependence on hard segment domain formation and indicated that the polymer containing the highest number of hydrolytically labile urea and urethane bonds exhibited the least degradation . The ability of a polyurethane material to form hard segment micro-domains may contribute to the formation of a protective structure for the hydrolysable hard segment linkages located within the micro-domains.

FEMS Microbiol Lett, 1997 Jul 1, 152(1), 141 - 7
Bioavailability and biodegradation of polycyclic aromatic hydrocarbons in soils; Smith MJ et al.; Inoculation of soil with bacteria (a Gram-negative rod {PD2} and a 4-membered consortium {DC1}) accelerated mineralisation of phenanthrene and pyrene (but not naphthalene) added individually to a pristine sand and a pristine organic soil . The half-life of naphthalene was 3.5 days in both soils whether inoculated or non-inoculated . However, the half-life of phenanthrene decreased from 86 days in non-inoculated sand soil and 80 days in the non-inoculated organic soil to 3.6 days in the sand and 3.1 days in organic soil when inoculated with PD2, and to 6.6 days in the sand and 8.7 days in the organic soil when inoculated with DC1 . Phenanthrene mineralisation ceased after 23 days in DC1-inoculated soil and was 71.3 +/- 3.6% (sand) and 63.3 +/- 2.8% (organic) . This compared with 96.8 +/- 3.8% (sand) 102.8 +/- 2.5% (organic) after 8 days in PD2-inoculated soil . Inoculation with DC1 (but not PD2) also accelerated mineralisation of pyrene, where the half-life decreased from 155 days to 18 days in the sand soil, and from 216 days to 33 days in organic soil.

J Biomed Mater Res, 1997 Jun 5, 35(3), 371 - 81
Use of surface-modifying macromolecules to enhance the biostability of segmented polyurethanes; Tang YW et al.; Polyurethanes are widely used as biomaterials for medical implants because of their excellent mechanical properties and moderate biocompatibility . However, the demand for more bioresistant and biocompatible polyurethanes to meet the needs of long-term implant devices still remains an important issue . Since most biological interactions with materials occur at the interface, a significant number of studies for improving the biocompatibility of polyurethanes have concentrated on surface modification . It is well known that additives used in polymeric materials as processing aids, mold releasing agents, antioxidants, etc., migrate to the surface and change the surface properties of the material . Under certain conditions polymeric additives may also migrate toward surfaces . This study describes two fluorine-containing, surface-modifying macromolecules (SMMs) that have been evaluated for their ability to inhibit polyurethane degradation . These materials actively migrate to the upper surface of a material film when they are mixed with a base polymeric materia . Contact angle measurements for the mixture of SMM with base polyurethane indicate that the surface becomes more hydrophobic after adding the SMMs, while X-ray photoelectron spectroscopy analysis shows an enrichment of fluorine on the polymer surfaces . Differential scanning calorimetry thermograms indicate that the micro-structure, as defined by the thermal transitions of the base polymer, are not altered by the addition of SMMs . Enzyme-induced biodegradation tests exhibit a significant reduction of polyurethane degradation in the presence of these surface-resident materials . The results indicate that the SMMs have the potential to resist hydrolytic degradation mediated by lysosomal enzymes while generating a surface chemistry on the native elastomer which is similar in nature to that of a fluoropolymer, e.g., Teflon.

J Biomed Mater Res, 1997 Jun 5, 35(3), 357 - 69
Effect of alternative crosslinking techniques on the enzymatic degradation of bovine pericardia and their calcification; Vasudev SC et al.; The in vitro calcification and enzymatic degradation of bovine pericardia (BP) after a series of surface treatments were studied as a function of exposure time . The degradation of these treated surfaces was monitored by scanning electron micrography and tensile strength measurements . Polyethylene glycol-(PEG) grafted BP and glutaraldehyde-(GA) treated BPs retained maximum stability in collagenase digestion compared with SDS-treated BP . The ability of alpha chymotrypsin, bromelain, esterase, trypsin, and collagenase to modulate the degradation of SDS-, GA-, PEG-, Carbodiimide-, and glycidylether-treated BPs also was investigated . Incubation of various enzymes to these crosslinked pericardia variably reduced the tensile strength of these tissues . It is conceivable that chemical treatments of pericardial tissues might have altered their physical and chemical configuration and the subsequent degradation properties . In vitro calcification studies showed a substantial reduction in the calcification profile of PEG-grafted bovine pericardia compared to other treated tissues . Furthermore, the biocompatibility aspects of pericardial tissues were established by platelet adhesion and octane contact angle . In conclusion, it seems that the surface modification of bovine pericardia via GA-PEG grafting may provide new ways of controlling biodegradation and calcification.

J Biomed Mater Res, 1997 Jun 5, 35(3), 319 - 28
The effect of strain state on the biostability of a poly(etherurethane urea) elastomer; Schubert MA et al.; The effect of deformation state on degradation of a PEUU without added stabilizers was examined in an oxidative environment that simulates the in vivo biodegradation of the polymer . Polymer tubes were stressed uniaxially and biaxially over glass mandrels and treated in 20% hydrogen peroxide/0.1 M cobalt chloride solution for 12 days at 37 degrees C . The amount of degradation was determined from the ATR-FTIR peak height of the amorphous aliphatic ether absorbance at 1110 cm-1 . If a uniaxial stress was applied, degradation was inhibited and the amount of surface ether remaining after treatment increased linearly with strain . If the stress was biaxial, the amount of degradation was not reduced unless the strain was greater than 200% . Decreased degradation correlated with the amount of soft-segment orientation . The decreased degradation rate was attributed to compaction of the polyether phase by orientation, which resulted in lower permeability to oxidative agents, particularly oxygen . Macroscopic damage was confined to a thin peeling surface layer if the stress was uniaxial . In comparison, biaxially stressed PEUU ruptured.

Genetika, 1997 Jun, 33(6), 762 - 8
{Genetic control of naphthalene biodegradation by a strain of Pseudomonas sp . 8909N}; Kosheleva IA et al.; The ability of Pseudomonas sp . 8909N to grow using Naphthalene and salicylate as the sole source of carbon and energy is mediated by the presence of an 80-kb conjugative pBS1145 plasmid in this strain . Structural genes for naphthalene degradation in pBS1145 plasmid are homologous to those in the known NAH7 plasmid . Conjugational transfer of pBS1145 from the original strain is accompanied by a deletion of a plasmid DNA fragment that does not affect the Nah+Sal+ phenotype . Plasmid pBS1145 specifies a low constitutive level of catechol-2,3-dioxygenase, the key enzyme of the metha-pathway of catechol degradation . Activity of this enzyme is induced in the presence of salicylate . Enzymes of both the metha and ortho-pathway of catechol degradation (catechol-2-3-dioxygenase) were shown to operate in the process of naphthalene degradation in Pseudomonas sp . 8909N . The ability of this strain to bring about transformation of polycyclic aromatic hydrocarbon phenanthrene is also controlled by pBS1145 plasmid.

Appl Microbiol Biotechnol, 1997 Jun, 47(6), 675 - 82
Pentachlorophenol biodegradation kinetics of an oligotrophic fluidized-bed enrichment culture; Melin ES et al.; A fluidized-bed reactor (FBR) was used to enrich an aerobic chlorophenol-degrading microbial culture . Long-term continuous-flow operation with low effluent concentrations selected oligotrophic microorganisms producing good-quality effluent for pentachlorophenol(PCP)-contaminated water . PCP biodegradation kinetics was studied using this FBR enrichment culture . The results from FBR batch experiments were modeled using a modified Haldane equation, which resulted in the following kinetic constants: qmax = 0.41 mg PCP mg protein-1 day-1, Ks = 16 micrograms l-1, Ki = 5.3 mg l-1, and n = 3.5 . These results show that the culture has a high affinity for PCP but is also inhibited by relatively low PCP concentrations (above 1.1 mg PCP l-1) . This enrichment culture was maintained over 1 year of continuous-flow operation with PCP as the sole source of carbon and energy . During continuous-flow operation, effluent concentrations below 2 micrograms l-1 were achieved at 268 min hydraulic retention time (tHR) and 2.5 mg PCP l-1 feed concentration . An increase in loading rate by decreasing tHR did not significantly deteriorate the effluent quality until a tHR decrease from 30 min to 21 min resulted in process failure . Recovery from process failure was slow . Decreasing the feed PCP concentration and increasing tHR resulted in an improved process recovery.

Chemosphere, 1997 Jun, 34(12), 2621 - 36
Biodegradation of sucrose poly fatty acid esters in soils; Figge K et al.; Sucrose polyesters (SPEs) were applied to soil at rates equivalent to 1062 to 1293 kg per hectare and incubated over periods of 100 to 403 days at 20 +/- 2 degrees C in darkness and at a soil moisture of 40% of the maximum water holding capacity . All applied forms of SPEs were aerobically biodegraded to some degree in both American and German soil . However, the mineralization rates varied considerably and were dependent on both SPE and soil type . For example, sucrose octaoleate underwent slow and limited mineralization in the German soils Speyer and Borstel as well as in the American soil Madera, reaching only 6.9-18.4% mineralisation after over 400 days incubation . The same material in the American soils Hollande, Thermal and Uvalde as well as in the German soil Speicherkoog, reached 35-52% after the same incubation period . Of the SPEs most realistic for use in food products, the more liquid (i.e . with the least saturated fatty acids) underwent the most rapid and extensive mineralization . However, the mineralization rates for these materials were distinctly lower than the corresponding ones for sucrose octaoleate . In all cases the extent of mineralization of the SPEs in soil was significantly lower than that of a control fat (synthetic triglyceride mixture HB307), which typically underwent over 50% mineralization in 60 days.

Lett Appl Microbiol, 1997 Jun, 24(6), 435 - 7
Co-metabolism and microbial growth in the biodegradation of alkylbenzenesulphonates; Marques ML et al.; Two organisms, CCMI507 and CCMI852, degrading undecylbenzenesulphonate (LAS) by the ortho- and meta-cleavage pathways were studied in cultures where glucose was used as carbon and energy source . CCMI507 (ortho-pathway) started the degradation of LAS at the beginning of the culture development in parallel with glucose utilization . The degradation followed a steady profile of degradation until 77% of LAS was degraded in the culture containing initially 5 mg l-1 of the compound and 81% in the cultures containing initially 10 and 20 mg l-1 of LAS, after 72 h fermentation . The organism CCMI852 (meta-pathway) started degrading the compound only after 20 h, when 75% of glucose was spent and well within the stationary-phase . After 72 h fermentation the level of degradation by CCMI852 varied from 70% (5 mg l-1 of LAS) to around 75% (10 and 20 mg l-1 of LAS).

Microbiology, 1997 Jun, 143 ( Pt 6), 1891 - 900
Effects of various types of stress on the metabolism of reserve carbohydrates in Saccharomyces cerevisiae: genetic evidence for a stress-induced recycling of glycogen and trehalose; Parrou JL et al.; It is well known that glycogen and trehalose accumulate in yeast under nutrient starvation or entering into the stationary phase of growth, and that high levels of trehalose are found in heat-shocked cells . However, effects of various types of stress on trehalose, and especially on glycogen, are poorly documented . Taking into account that almost all genes encoding the enzymes involved in the metabolism of these two reserve carbohydrates contain between one and several copies of the stress-responsive element (STRE), an investigation was made of the possibility of a link between the potential transcriptional induction of these genes and the accumulation of glycogen and trehalose under different stress conditions . Using transcriptional fusions, it was found that all these genes were induced in a similar fashion, although to various extents, by temperature, osmotic and oxidative stresses . Experiments performed with an msn2/msn4 double mutant proved that the transcriptional induction of the genes encoding glycogen synthase (GSY2) and trehalose-6-phosphate synthase (TPS1) was needed for the small increase in glycogen and trehalose upon exposure to a mild heat stress and salt shock . However, the extent of transcriptional activation of these genes upon stresses in wild-type strains was not correlated with a proportional rise in either glycogen or trehalose . The major explanation for this lack of correlation comes from the fact that genes encoding the enzymes of the biosynthetic and of the biodegradative pathways were almost equally induced . Hence, trehalose and glycogen accumulated to much higher levels in cells lacking neutral trehalose or glycogen phosphorylase exposed to stress conditions, which suggested that one of the major effects of stress in yeast is to induce a wasteful expenditure of energy by increasing the recycling of these molecules . We also found that transcriptional induction of STRE-controlled genes was abolished at temperatures above 40 degree C, while induction was still observed for a heat-shock-element regulated gene . Remarkably, trehalose accumulated to very high levels under this condition . This can be explained by a stimulation of trehalose synthase and inhibition of trehalose by high temperature.

Microbiol Mol Biol Rev, 1997 Jun, 61(2), 121 - 35
Fate and activity of microorganisms introduced into soil; van Veen JA et al.; Introduced microorganisms are potentially powerful agents for manipulation of processes and/or components in soil . Fields of application include enhancement of crop growth, protection of crops against plant-pathogenic organisms, stimulation of biodegradation of xenobiotic compounds (bioaugmentation), and improvement of soil structure . Inoculation of soils has already been applied for decades, but it has often yielded inconsistent or disappointing results . This is caused mainly by a commonly observed rapid decline in inoculant population activity following introduction into soil, i.e., a decline of the numbers of inoculant cells and/or a decline of the (average) activity per cell . In this review, we discuss the available information on the effects of key factors that determine the fate and activity of microorganisms introduced into soil, with emphasis on bacteria . The factors addressed include the physiological status of the inoculant cells, the biotic and abiotic interactions in soil, soil properties, and substrate availability . Finally, we address the possibilities available to effectively manipulate the fate and activity of introduced microorganisms in relation to the main areas of their application.

Biomaterials, 1997 Jun, 18(11), 815 - 21
Denatured thiolated collagen . II . Cross-linking by oxidation; Nicolas FL et al.; We have recently described a new method for the thiolation of denatured collagen, which allows precise amounts of SH groups to be attached onto the protein backbone . The oxidation of denatured thiolated collagen produces disulphide cross-linking . The cross-linking of these products has been studied, optimized and compared to the cross-linking of native and denatured collagen with 0.5% aqueous glutaraldehyde . Films have been prepared and their tensile mechanical properties and biodegradation rates with trypsin and collagenase have been evaluated . Our results indicate that the cross-linking in oxidized thiolated collagen depends on the number of the disulphide bridges formed and on their intermolecular versus intramolecular repartition . Since the number of disulphide bridges can be controlled by the level of thiol in the denatured collagen and by the oxidation procedure, it is possible to control the mechanical properties and the biodegradation rates of these new materials . Under optimized conditions, oxidized denatured thiolated collagen films are more resistant and rigid than glutaraldehyde-cross-linked collagen films Cross-linked thiolated collagen materials are also more resistant to collagenase degradation . However, because of the loss of the triple-helical structure, they are more susceptible to trypsin degradation relative to glutaraldehyde-cross-linked triple-helical collagen . Denatured collagen cross-linked by physiological bridges such as disulphide bridges, with controllable mechanical properties and biodegradation rates, is of considerable interest in biomedical applications.

J Pediatr Surg, 1997 May, 32(5), 717 - 20
Tissue compatibility and biodegradation of new absorbable stents for tracheal stabilization: an experimental study; Lochbihler H et al.; Newly designed absorbable stents for temporary tracheal stabilization were implanted into the trachea of 35 Wistar rats . The stents consisted of Vicryl filaments in a homogeneous PDS melt . Compatibility and biodegradation were investigated over a study period of up to 24 weeks . After the animals were killed, the trachea was examined with an optic and scanning electron microscope . During the first 2 weeks erosive mucosal defects appeared in the trachea, as well as distinct polyps of granulation tissue, focal metaplasia of the epithelium, and inflammatory infiltrates of the lamina propria . During the period leading to the sixth week, the granulations flattened and mild fibrotic alterations evolved . After the eighth week no stent residues could be detected, whereas only slight signs of chronic fibrotic inflammation persisted . No evidence for aspiration of foreign bodies or progressive inflammatory changes of the mediastinum was found.

Cornea, 1997 May, 16(3), 352 - 9
Histologic evaluation during healing of hydrogel core-and-skirt keratoprostheses in the rabbit eye; Vijayasekaran S et al.; PURPOSE: We developed two models that are modifications of our original poly(2-hydroxyethyl methacrylate) (PHEMA) core-and-skirt keratoprosthesis . In these keratoprostheses, the mechanical strength of the skirt has been considerably increased with divinyl glycol (DVG) as a cross-linking agent during polymerization . In one (KPro I), methyl methacrylate (MMA) was added as comonomer to increase cell adhesion, and in the other (KPro II), HEMA was polymerized with DVG without comonomer . The aim of this study was to evaluate the process of healing and biocolonization and to ascertain whether KPro I demonstrates better ingrowth than the mechanically stronger KPro II, after implantation in rabbit eyes . METHODS: Ten rabbits were used for each model and studied at five predetermined end points up to 26 weeks . The device was implanted as a full-thickness keratoprosthesis covered with a conjunctival flap . RESULTS: Neither prosthesis demonstrated extrusion or retroprosthetic membrane formation . There was no significant difference between the two types of prosthesis with respect to tissue ingrowth and surrounding tissue melting . Histologically, inflammation was not severe, but calcification was seen in most specimens . Evidence of biodegradation of the prosthesis also was seen . CONCLUSION: In our original keratoprosthesis, fibrovascular invasion had occurred into the prosthetic skirt, but wound dehiscence and low mechanical strength resulted in an unfavorable outcome . In this series, the mechanical properties were improved, and KPro II was stronger than KPro I . Therefore KPro II would be the preferred polymer combination for surgical manipulation . However, biodegradation and calcification require further investigation into the degree and significance of these adverse reactions.

Appl Environ Microbiol, 1997 May, 63(5), 1933 - 8
Plant compounds that induce polychlorinated biphenyl biodegradation by Arthrobacter sp . strain B1B; Gilbert ES et al.; Plant compounds that induced Arthrobacter sp . strain B1B to cometabolize polychlorinated biphenyls (PCBs) were identified by a screening assay based on the formation of a 4,4'-dichlorobiphenyl ring fission product . A chemical component of spearmint (Mentha spicata), l-carvone, induced Arthrobacter sp . strain B1B to cometabolize Aroclor 1242, resulting in significant degradation of 26 peaks in the mixture, including selected tetra- and pentachlorobiphenyls . Evidence for PCB biodegradation included peak disappearance, formation of a phenylhexdienoate ring fission product, and chlorobenzoate accumulation in the culture supernatant . Carvone was not utilized as a growth substrate and was toxic at concentrations of greater than 500 mg liter-1 . Several compounds structurally related to l-carvone, including limonene, p-cymene, and isoprene, also induced cometabolism of PCBs by Arthrobacter sp . strain B1B . A structure-activity analysis showed that chemicals with an unsaturated p-menthane structural motif promoted the strongest cometabolism activity . These data suggest that certain plant-derived terpenoids may be useful for promoting enhanced rates of PCB biodegradation by soil bacteria.

J Biomed Mater Res, 1997 May, 35(2), 137 - 45
Glutaraldehyde crosslinking of collagen substrates inhibits degradation in skin substitutes grafted to athymic mice; Harriger MD et al.; Collagen-based implants have been described as vehicles for transplantation of cultured skin cells for treatment of burn wounds . To optimize vascularization and repair of connective tissue, collagen solubility and glutaraldehyde crosslinking were evaluated . Cultured skin substitutes consisted of human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan substrates that were prepared from acid-insoluble, or partially soluble collagen . Substrates were crosslinked with 0% or 0.25% glutaraldehyde, populated with cells, and grafted to full-thickness wounds on athymic mice (n = 6/condition) . After 6 weeks, the wound area was measured by planimetry, and healed wounds were scored by histochemistry for immunoreactivity to HLA-ABC and bovine collagen . Data analysis shows that crosslinking of collagen implants with glutaraldehyde is associated (p < 0.001) with detection of the implant . No association was found between solubility of bovine collagen and immunodetection . Epidermis of all wounds was positive for HLA-ABC, and no differences in wound areas were found . These results suggest that glutaraldehyde crosslinking of collagen implants decreases the rate of biodegradation . Delayed degradation of crosslinked collagen may result clinically in reduced engraftment of skin substitutes.

J Neurosurg, 1997 May, 86(5), 871 - 5
Potential efficacy of basic fibroblast growth factor incorporated in biodegradable hydrogels for skull bone regeneration; Yamada K et al.; Biodegradable gelatin hydrogels incorporating basic fibroblast growth factor (bFGF) were evaluated for their efficacy in bone regeneration using a rabbit model . Hydrogels with water contents of 85% and 98% were prepared using chemical crosslinking of gelatin with an isoelectric point of 4.9 in aqueous solution and, after freeze drying, were impregnated with an aqueous solution of bFGF to obtain bFGF-incorporated gelatin hydrogels . When they were implanted into bone defects measuring 6 mm in diameter in rabbit skulls (six animals/group), complete closure of the defect was observed at 12 weeks after implantation, regardless of the water content of the hydrogels . In contrast, bFGF did not enhance bone regeneration when applied to the skull defect in solution with phosphate-buffered saline (PBS) . Also, gelatin hydrogels lacking bFGF were not effective in inducing bone formation, with fibrous tissue growing into the defect instead, similar to the skull defect seen in control rabbits treated with PBS . This indicates that the presence of hydrogels did not interfere with bone regeneration at the skull defect, probably because of their disappearance during biodegradation . It is concluded that the gelatin hydrogel is a promising matrix for effective induction of biological activity of bFGF for bone regeneration in skull and sinus defects.

FEBS Lett, 1997 Apr 21, 407(1), 69 - 72
Characterization of an intradiol dioxygenase involved in the biodegradation of the chlorophenoxy herbicides 2,4-D and 2,4,5-T; Travkin VM et al.; Hydroxyquinol 1,2-dioxygenase, an intradiol dioxygenase, which catalyzes the cleaving of the aromatic ring of hydroxyquinol, a key intermediate of 2,4-D and 2,4,5-T degradation, was purified from Nocardioides simplex 3E cells grown on 2,4-D as the sole carbon source . This enzyme exhibits a highly restricted substrate specificity and is able to cleave hydroxyquinol (K(m) for hydroxyquinol as a substrate was 1.2 microM, V(max) 55 U/mg, K(cat) 57 s-1 and K(cat)/K(m) 47.5 microM s-1), 6-chloro- and 5-chlorohydroxyquinol . Different substituted catechols and hydroquinones are not substrates for this enzyme . This enzyme appears to be a dimer with two identical 37-kDa subunits . Protein and iron analyses indicate an iron stoichiometry of 1 iron/65 kDa homodimer, alpha2 Fe . Both the electronic absorption spectrum which shows a broad absorption band with a maximum at 450 nm and the electron paramagnetic resonance spectra are consistent with a high-spin iron(III) ion in a rhombic environment typical of the active site of intradiol cleaving enzymes.

J Biomater Appl, 1997 Apr, 11(4), 430 - 52
Influence of polyethylene glycol graftings on the in vitro degradation and calcification of bovine pericardium; Vasudev SC et al.; Calcification is a frequent cause of the clinical failure of bio-prosthetic heart valves fabricated from glutaraldehyde pretreated bovine pericardium (GATBP) . This article reports on various chemical techniques for grafting polyethylene glycol (PEG) on bovine pericardium, their biostability, and calcification . The process of calcification profile was studied by in vitro experiments via the incubation of pericardial samples in a metastable solution of calcium phosphate . The calcification profile of PEG-modified bovine pericardium through glutaraldehyde linkages was significantly reduced compared to other methods of grafting . The mechanical property of these PEG-modified tissues after enzyme (collagenase) digestion and calcification were also investigated . PEG grafting of BP via glutaraldehyde or hexamethylene diisocyanate had shown better mechanical stability compared to other grafting methods used . In conclusion, it seems that the surface modification of bovine pericardium through high molecular weight PEGs via glutaraldehyde linkages may provide new ways of controlling tissue biodegradation and calcification.

Ecotoxicol Environ Saf, 1997 Apr, 36(3), 288 - 96
Stream periphytic biodegradation of the anionic surfactant C12-alkyl sulfate at environmentally relevant concentrations; Lee DM et al.; The effects of continuous exposure to C12-alkyl sulfate on a periphytic microbial community were determined in an 8-week stream mesocosm study . C12-alkyl sulfate concentrations ranged from environmentally relevant (< 10-20 micrograms/liter) to unrealistically high concentrations (> 1500 micrograms/liter) . Endpoints evaluated included turnover rates, bacterial cell density, heterotrophic mixed amino acid uptake, and fatty acid profile evaluations . Predosed periphyton demonstrated a mean turnover rate for C12-alkyl sulfate of 0.08/hr . During the 8-week dosing period, a significant increase in mean turnover rates was observed in streams dosed with > or = 61 micrograms C12-alkyl sulfate/liter, despite a 10 degrees C drop in stream temperature . A significant correlation between turnover rate and C12-alkyl sulfate concentration was also observed . While bacterial cell density increased during the study, it was determined that the biodegradation acclimation to C12-alkyl sulfate was not biomass-specific . Likewise, bacterial activity generally increased over the study, but it did not correlate with either biodegradation or bacterial cell density . Lastly, phospholipid fatty acid profiles indicate that a shift in the microbial community occurred in the high-dose stream as opposed to the control stream . This study demonstrates that C12-alkyl sulfate is rapidly degraded and induces a biodegradative acclimation response at environmentally relevant concentrations.

Lett Appl Microbiol, 1997 Apr, 24(4), 229 - 32
Biodegradation of lantadene A, the pentacyclic triterpenoid hepatotoxin by Pseudomonas pickettii; Sharma OP et al.; A bacterial strain capable of biodegradation of lantadene A (22 beta-angeloyloxy-3-oxoolean-12-en-28-oic acid) has been isolated from soil using lantadene A as the sole carbon source . The organism is rod shaped, Gram negative, motile and has been identified as Pseudomonas pickettii . This is the first report of the biodegradation of a pentacyclic triterpenoid.

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