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| Appl Environ Microbiol, 1992 Mar, 58(3), 953 - 60 Soluble methane monooxygenase component B gene probe for identification of methanotrophs that rapidly degrade trichloroethylene; Tsien HC et al.; Restriction fragment length polymorphisms, Western blot (immunoblot) analysis, and fluorescence-labelled signature probes were used for the characterization of methanotrophic bacteria as well as for the identification of methanotrophs which contained the soluble methane monooxygenase (MMO) gene and were able to degrade trichloroethylene (TCE) . The gene encoding a soluble MMO component B protein from Methylosinus trichosporium OB3b was cloned . It contained a 2.2-kb EcoRI fragment . With this cloned component B gene as probe, methanotroph types I, II, and X and environmental and bioreactor samples were screened for the presence of the gene encoding soluble MMO . Fragments produced by digestion of DNA with rare cutting restriction endonucleases were separated by pulsed-field gel electrophoresis and transferred to Zeta-Probe membrane (Bio-Rad) for Southern blot analysis . Samples were also analyzed for the presence of soluble MMO by Western blot analysis and the ability to degrade TCE . The physiological groups of methanotrophs in each sample were determined by hybridizing cells with fluorescence-labelled signature probes . Among twelve pure or mixed cultures, DNA fragments of seven methanotrophs hybridized with the soluble MMO B gene probe . When grown in media with limited copper, all of these bacteria degraded TCE . All of them are type II methanotrophs . The soluble MMO component B gene of the type X methanotroph, Methylococcus capsulatus Bath, did not hybridize to the M . trichosporium OB3b soluble MMO component B gene probe, although M . capsulatus Bath also produces a soluble MMO. Biotechniques, 1992 Feb, 12(2), 258 - 63 Use of perfluorocarbon emulsions in cell culture; Ju LK et al.; Perfluorocarbon emulsions were applied to hybridoma cultures grown in tissue culture tubes and column bioreactors . The oxygen transfer enhancement effect of perfluorocarbon emulsions was clearly demonstrated by the higher cell densities obtained in emulsion-supplemented systems . In addition, perfluorocarbon emulsions were shown to provide better cell suspension in a low-shear environment . The study in column bioreactors also suggested a cell protective effect of the employed perfluorocarbon emulsions in reducing the damage to cells by gas bubbles. Int J Artif Organs, 1992 Feb, 15(2), 126 - 30 Membrane bioreactors as hybrid artificial pancreas: experimental evaluation; Lombardi CP et al.; Results of cultured islet transplantation in the management of insulin-dependent diabetes are still unsatisfactory . The main problem preventing success is the swift and resolute host immune rejection . To obviate this we designed and experimented a model of bioartificial pancreas, made of polymeric hollow fibers, put into the blood circulation as an artero-venous bypass to immunoisolate endocrine tissue from leucocytes and immunoglobulins . We tested four different membrane bioreactors (BR1-4) . BR1 and 2 had seven hollow fibers, the others more than 6,000 smaller fibers . In BR4 a connecting tube with a high-permeability membrane was inserted between the islet compartment and the bioreactor outlet to improve the ultrafiltration flow . In vitro, the islets inside the bioreactor perfused with glucose solutions (300 mg%) showed a rapid, high insulin secretory response, related to the glucose stimulation . The use of the outside connection allowed a twofold increase of insulin production. Protein Expr Purif, 1992 Feb, 3(1), 27 - 35 Purification of recombinant human secretory phospholipase A2 (group II) produced in long-term immobilized cell culture; Levin W et al.; Recombinant human secretory phospholipase A2 (Group II) was expressed in long-term culture of immobilized Chinese hamster ovary cells utilizing a continuous-perfusion airlift bioreactor . The bioreactor was continuously perfused with cell-culture medium supplemented with 5% fetal calf serum at an average flow rate of 5 liters/day for 30 days . Recombinant phospholipase A2, at concentrations ranging from 100 to 500 micrograms/liter, was purified to apparent homogeneity by an efficient two-step procedure involving a silica-based cation-exchange resin and hydrophobic interaction chromatography (greater than 65% recovery of phospholipase A2) . The purified recombinant protein has an apparent molecular weight of 16 kDa, identical to that of purified human placental or synovial fluid phospholipase A2, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis . Application of the purified protein onto several different gel filtration columns resulted in elution of the protein at molecular weights corresponding to 3.1-4.7 kDa, suggesting an interaction of the protein with the column resins . However, analytical ultracentrifugation experiments revealed that the protein behaves as a monomer (13.8-14.2 kDa) over a protein concentration range of approximately 10 micrograms/ml to 5 mg/ml . With autoclaved Escherichia coli membranes as substrate, the recombinant protein has catalytic properties (pH optimum, effects of bovine serum albumin, sodium chloride concentration, and requirement for calcium) similar to those of the protein purified from human placenta. Appl Microbiol Biotechnol, 1992 Feb, 36(5), 611 - 7 Growth characteristics of Sanguinaria canadensis L . cell suspensions and immobilized cultures for production of benzophenanthridine alkaloids; Rho D et al.; Sanguinaria canadensis L . plants were harvested from a local forest and calli were initiated from leaf explants . The production of benzophenanthridine alkaloids (i.e . sanguinarine, sanguilutine, sanguirubine, chelerythrine, chelilutine and chelirubine) by S . canadensis cell grown in modified B5 and IM2 media was compared to the alkaloid content of rhizomes . Sanguinarine accounted for approximately 80% of the total alkaloid content of cultured cells (1.3%, g g-1) while sanguinarine and sanguirubine accounted for 70% of rhizome alkaloids (9.0%, g g-1) . Sanguinarine, chelirubine and chelerythrine were the only known alkaloids detected in cultured S . canadensis cells . Maximum alkaloid production of cultures performed using B5 medium, containing half the original nitrate concentration, was observed following extracellular nitrate and sugar depletion . The scale-up of this culture was successfully performed in a 2-1 immobilization bioreactor . The consumption of sugar and nitrate as well as the oxygen (OTR) and carbon dioxide (CTR) transfer rates of the immobilized cell culture were monitored for 15 days . The maximum sugar and nitrate consumption rates were 1.8 g l-1 per day and 2.3 mM per day respectively . The maximum OTR and CTR of the immobilized cell culture were 0.8 mmol O2 l-1 h-1 and 0.95 mmol CO2 l-1 h-1 respectively . The sanguinarine yield of this culture reached 1.0% based on biomass dry weight (g g-1 dw) by day 15. J Biotechnol, 1992 Feb, 22(3), 311 - 27 Cultivation of animal cells in a reticulated vitreous carbon foam; Kent BL et al.; A reticulated vitreous carbon foam (RVCF) was used as a surface to cultivate a model anchorage-dependent animal cell line, 3T6 (mouse embryo fibroblast) . This fixed-surface bioreactor provided a low-shear, chemically-inert, and reusable environment for cell growth . An external medium recirculation loop allowed aeration, nutrient monitoring, and medium replacement without disturbing the cells . Optimal flow rates for the attachment and growth phases were determined . Growth rates comparable to static (T-flask and petri dish) cultures and agitated microcarrier cultures were achieved with appropriately high medium recirculation rates . Metabolic parameters were shown to be useful indicators of cell mass, although specific glucose consumption rates were considerably higher for cultures in the RVCF reactor . Oxygen supply was shown to be the most likely limiting factor for scaleup. J Biotechnol, 1992 Feb, 22(3), 291 - 8 Continuous beta-galactosidase production with a recombinant baculovirus insect-cell system in bioreactors; van Lier FL et al.; Insect cells were exploited to produce bacterial beta-galactosidase by infecting them with a recombinant nuclear polyhedrosis virus (baculovirus) of Autographa californica . The insect cells were cultured in a continuous stirred tank reactor (CSTR) and led to a second CSTR where they were infected with a recombinant virus in which the lacZ gene from Escherichia coli was inserted . In the effluent of the production reactor, maximum activities of 15 units beta-galactosidase per 10(6) cells were measured . For about 25 d beta-galactosidase production remained constant, but then rapidly declined . This drop was due to a decrease in production of active beta-galactosidase rather than to inactivation of this enzyme . It was concluded that the reduced production was due to reduced polyhedrin promoter-driven synthesis. J Biotechnol, 1992 Feb, 22(3), 245 - 70 Further studies of the culture of mouse hybridomas in an agitated bioreactor with and without continuous sparging; Oh SK et al.; TB/C3 mouse hybridoma cells have been grown at 2 controlled dO2 conditions by headspace and sparged oxygenation . Also a variety of sparging rates and sparger sizes and positions have been employed . Headspace oxygenation at dO2 levels from 5% to 100% of saturation give essentially the same performance as controls . Sparging is generally damaging to cells, the extent of damage decreasing with reduced sparging rate until at below about 0.02 vvm results equivalent to the unsparged conditions are obtained . Damage is clearly linked with bubble-cell interactions at the air-medium interface where bubbles bursting in clusters and of a size less than 5 mm appear to be the most lethal . When the interaction of air sparging with the agitator flow leads to an increase in the number of smaller bubbles and cluster bursts, cell damage is further increased . Pluronic F-68 reduces damage very significantly . Biological aspects are briefly discussed in the light of various biological tests . The practical implications of this work for large scale, free suspension cell culture are outlined. In Vitro Cell Dev Biol, 1992 Jan, 28A(1), 47 - 60 Morphologic differentiation of colon carcinoma cell lines HT-29 and HT-29KM in rotating-wall vessels; Goodwin TJ et al.; A new low shear stress microcarrier culture system has been developed at NASA's Johnson Space Center that permits three-dimensional tissue culture . Two established human colon adenocarcinoma cell lines, HT-29, an undifferentiated, and HT-29KM, a stable, moderately differentiated subline of HT-29, were grown in new tissue culture bioreactors called Rotating-Wall Vessels (RWVs) . RWVs are used in conjunction with multicellular cocultivation to develop a unique in vitro tissue modeling system . Cells were cultivated on Cytodex-3 microcarrier beads, with and without mixed normal human colonic fibroblasts, which served as the mesenchymal layer . Culture of the tumor lines in the absence of fibroblasts produced spheroidlike growth and minimal differentiation . In contrast, when tumor lines were co-cultivated with normal colonic fibroblasts, initial growth was confined to the fibroblast population until the microcarriers were covered . The tumor cells then commenced proliferation at an accelerated rate, organizing themselves into three-dimensional tissue masses that achieved 1.0- to 1.5-cm diameters . The masses displayed glandular structures, apical and internal glandular microvilli, tight intercellular junctions, desmosomes, cellular polarity, sinusoid development, internalized mucin, and structural organization akin to normal colon crypt development . Differentiated samples were subjected to transmission and scanning electron microscopy and histologic analysis, revealing embryoniclike mesenchymal cells lining the areas around the growth matrices . Necrosis was minimal throughout the tissue masses . These data suggest that the RWV affords a new model for investigation and isolation of growth, regulatory, and structural processes within neoplastic and normal tissue. Adv Biochem Eng Biotechnol, 1992, 46, 187 - 223 Modelling the growth of filamentous fungi; Nielsen J; Despite the considerable industrial importance of filamentous fungi there have been very few attempts to model the complex growth process of these microorganisms . With a new generation of high performance, computerized bioreactors and new analytical techniques it is possible to obtain the necessary experimental data for setting up reliable structured models describing the growth process of filamentous fungi . It is therefore interesting to review the mathematical models described previously in the literature and the experimental data on which these models are built . Only structured models are considered due to the complex metabolism of filamentous fungi and to the natural cellular structuring of the biomass, i.e . the biomass can be divided into different cell types . In order to set up good structured models it is strictly necessary to have a detailed knowledge of the mechanisms underlying the growth process . This involves both biochemical insight and understanding of the interactions between different macromolecules and cytological organelles. Folia Microbiol (Praha), 1992, 37(2), 133 - 9 Phenomenological theory of substrate-induced acidification with application to Candida utilis dissimilating ethanol; Votruba J et al.; The mathematical theory of substrate-induced acidification by microorganisms was based on special formulation of mass and charge conservation laws for distinct species . The strength of the theory was tested on the ethanol-induced acidification by Candida utilis in pure water and in phthalate buffer . We showed that the theory may be used to approximate, extrapolate and predict the course of apparent acidification including the effects of buffering capacity of the broth . It makes it possible to formulate mathematical models that are suitable for process simulation and computer control of bioreactors when pH is used as a state variable. Vaccine, 1992, 10(13), 896 - 9 Contribution to rabies prevention; Sureau P; After the end of the Second World War, an outbreak of fox rabies invaded Europe . For the immunization of human populations and domestic animals against the risk of rabies transmitted by infected wild animals, it appeared necessary to replace the first generation of rabies vaccines (nerve tissue vaccines) by more potent and safer vaccines . The European vaccine manufacturers, in close collaboration with the research institutes engaged in rabies research, soon and quickly developed a second generation of rabies vaccines, produced in cell cultures including continuous cell lines grown in bioreactors of industrial scale . The third generation of rabies vaccines is already available: the vaccinia-rabies glycoprotein recombinant vaccine is presently applied on a large scale in some European countries for immunization of wildlife . The canarypox recombinant vaccine has already been considered and successfully tested for human immunization. Biomater Artif Cells Immobilization Biotechnol, 1992, 20(5), 1177 - 92 Hybrid artificial pancreas: islet transplantation inside membrane bioreactors; Lombardi CP et al.; The use of pancreatic islet transplantation in membrane bioreactors put in vascular circuits aims at resetting the glucose homeostasis in diabetic or pancreatectomized patients, avoiding immune host rejection . Our experience was carried out at following stages: porcine pancreas explantation and enzymatic separation of endocrine tissue from exocrine fraction by collagenase; evaluation of islet functionality (culture tests); in vitro tests of the islets-bioreactor system, to assess the metabolic response to the glucose; in vivo evaluation to assay the haemodynamic behaviour . The trials showed a good metabolic bioreactor functionality and a decreasing incidence of coagulative problems. Res Exp Med (Berl), 1992, 192(5), 305 - 16 Bioartificial endocrine pancreas: foreign-body reaction and effectiveness of diffusional transport of insulin and oxygen after long-term implantation of hollow fibers into rats; Bodziony J; Foreign body reaction of the liver, kidney, and subcutaneous tissue of rats after implantation of hollow fibers (HF) for 1, 3, 6, and 12 months and its influence on the effectiveness of diffusional transport of insulin and oxygen were investigated . The highest degree of fibrosis was observed after subcutaneous implantation of HF and the lowest degree after implantation into the kidney . Histochemical staining of the fibrous capsule showed a tissue-dependent domination of the collagenous fibrils . After 90 min of perfusion 33% of the insulin contained in HF diffused out of the nonimplanted fiber, after 120 min, 73% and after 180 min, 100% . Hollow fibers, which were removed with a surrounding connective capsule after an implantation period of 1 year, showed even better permeability for insulin than nonimplanted HF . The tension of oxygen in the lumen of the implanted hollow fibers was 42 mm Hg after implantation into the kidney and 30 mmHg after implantation into the liver . The oxygen present inside an HF that is implanted into a kidney and liver was consumed by 100 islets in 3.9 and 2.8 min, respectively . It was concluded that to achieve acceptable results in the construction of bioartificial pancreas more research activities should be performed on the diffusion and consumption of oxygen in the bioreactor. Cytotechnology, 1992, 9(1-3), 59 - 67 Optimal medium use for continuous high density perfusion processes; Buntemeyer H et al.; For maintenance of high cell density in continuous perfusion processes not only feeding with substrates but also removal of inhibitors and toxic waste products are of special interest . High perfusion rates cause large volumes of product containing medium which have to be processed in product isolation . In order to minimize these volumes concentrated feed solutions of optimized medium are used . On the other hand, such media may cause high concentrations of toxic or inhibitory metabolites which can negatively influence cell growth and product formation . Especially, if the spent medium (or special parts of it) is used again after product isolation, the removal or even better the control of inhibitor production is of highest importance . We have developed a continuous fermentation concept and system (continuous medium cycle bioreactor, cMCB) in which both limitation and inhibition effects can be generated to identify special substances as limiting or inhibitory components . With the results from those experiments it was possible to lower the total perfusion rate during serum-free perfusion cultures of hybridoma cells and to obtain an optimal substrate utilization . The advantages for decreasing the production costs (for media, special supplements and product isolation) are obvious . The other aim of this study was to identify secreted metabolic waste products as inhibitor or toxic metabolite. Cytotechnology, 1992, 9(1-3), 51 - 7 The membrane dialysis bioreactor with integrated radial-flow fixed bed--a new approach for continuous cultivation of animal cells; Bohmann A et al.; A hybridoma cell was cultivated continuously in a membrane dialysis bioreactor with an integrated radial-flow fixed bed consisting of porous Siran carriers over a period of 6 weeks . Antibodies accumulated to an average of 100 mg l-1, approx . 10 times more than in fixed bed cultures without dialysis membrane . Serum costs could be reduced about 85% due to an appropriate feeding strategy . Siran carriers with 3-5 mm diameter showed an advantage compared to those with 1-2 mm diameter . For the 3-5 mm carrier the specific glucose uptake rate and the MAb production rate were constant, if the velocity was between 0.09 mm s-1 and 0.75 mm s-1 . At higher velocities cells are washed out of the bed . Furthermore antibody consistency and cell stability were verified in long-term cultivations over a period of 96 days . From an estimation of the antibody concentration reachable with the reactor concept under optimal conditions a concentration 45 times higher compared to axial-flow fixed bed reactors and 11 times higher compared to stirred tank reactors can be expected. Cytotechnology, 1992, 9(1-3), 41 - 9 Modified CelliGen-packed bed bioreactors for hybridoma cell cultures; Wang G et al.; This study describes two packed bed bioreactor configurations which were used to culture a mouse-mouse hybridoma cell line (ATCC HB-57) which produces an IgG1 monoclonal antibody . The first configuration consists of a packed column which is continuously perfused by recirculating oxygenated media through the column . In the second configuration, the packed bed is contained within a stationary basket which is suspended in the vessel of a CelliGen bioreactor . In this configuration, recirculation of the oxygenated media is provided by the CelliGen Cell Lift impeller . Both configurations are packed with disk carriers made from a non-woven polyester fabric . During the steady-state phase of continuous operation, a cell density of 10(8) cells per cm3 of bed volume was obtained in both bioreactor configurations . The high levels of productivity (0.5 gram MAb per 1 of packed bed per day) obtained in these systems demonstrates that the culture conditions achieved in these packed bed bioreactors are excellent for the continuous propagation of hybridomas using media which contains low levels (1%) of serum as well as serum-free media . These packed bed bioreactors allow good control of pH, dissolved oxygen and temperature . The media flows evenly over the cells and produces very low shear forces . These systems are easy to set up and operate for prolonged periods of time . The potential for scale-up using Fibra-cel carriers is enhanced due to the low pressure drop and low mass transfer resistance, which creates high void fraction approaching 90% in the packed bed. Cytotechnology, 1992, 9(1-3), 3 - 9 Maximisation of perfusion systems and process comparison with batch-type cultures . Maximisation of perfusion cultures; Griffiths JB et al.; A comparison of cell yields and monoclonal antibody productivity from the same hybridoma has been made in a wide range of cell bioreactors including both batch and continuous perfusion cultures . The most productive systems were based on porous microcarriers in fixed and fluidised beds which can be operated with a high degree of efficiency and reliability from the physico-chemical engineering point of view . Further improvements should be possible by improving the physiological environment in dense cell cultures, as indicated by the preliminary studies that are described . These include experimental data showing the relationship between monoclonal antibody production rates with glucose, glutamine, ammonia, and oxygen levels in microporous beads . The results strongly indicate that perfusion processes that are scaleable in both volume and cell density can significantly reduce production costs . Manufacturers of biologicals from animal cells now have a choice between the proven batch-type processes and reliable perfusion systems based on microporous beads. Cytotechnology, 1992, 9(1-3), 29 - 40 Design and performance of a trickle-bed bioreactor with immobilized hybridoma cells; Phillips HA et al.; A trickle-bed system employing inert matrices of vermiculite or polyurethane foam packed in the downcomer section of a split-flow air-lift reactor has been developed for hybridoma culture to enhance antibody productivity . This quiescent condition favoured occlusion and allowed the cells to achieve densities twelve fold greater (12.8 x 10(6) cells/ml reactor for polyurethane foam) than in free cell suspension . The reactor was operated in a cyclic batch mode whereby defined volumes of medium were periodically withdrawn and replaced with equal volumes of fresh medium . The pH of the medium was used as the indicator of the feeding schedule . Glucose, lactate and ammonia concentrations reached a stationary value after 5 days . With vermiculite packing, a monoclonal antibody (MAb) concentration of 2.4 mg/l was achieved after 12 days . The MAb concentration declined then increased to a value of 1.8 mg/l . In the polyurethane foam average monoclonal antibody (MAb) concentrations reached a stationary value of 1.1 mg/l in the first 20 days and increased to a new stationary state value of 2.1 mg/l for the remainder of the production . MAb productivity in the trickle-bed reactor was 0.3 mg/l.d (polyurethane foam) and 0.18 mg/l.d (vermiculite) in comparison to 0.12 mg/l.d for free cell suspension . This trickle-bed system seems to be an attractive way of increasing MAb productivity in culture. Cytotechnology, 1992, 9(1-3), 141 - 7 Recombinant protein production in insect cell cultures infected with a temperature-sensitive baculovirus; Wu J et al.; Spodoptera frugiperda (IPLB-SF-21) insect cells were grown in shake-flasks and infected with a temperature-sensitive baculovirus to express the gene of chloramphenicol acetyl transferase (CAT) in serum-free medium (SF-900) and two serum-supplemented media (IPL-41 and Grace's) . In temperature-shift experiments (cell growth at 33 degrees C followed by virus replication at 27 degrees C 3-4 days later), virus and CAT production were much poorer in the serum-free medium than in serum-supplemented media, though cell growth was virtually the same in the different media tested . In all the three media, highest virus and CAT titers were obtained at the lowest MOI (multiplicity of infection 0.02) . This result is contrary to that obtained in constant-temperature culture (27 degrees C for both cell growth and virus replication) . Virus and CAT production was greatly improved when the entire culture was run at constant temperature . It appeared that infected cells were severely damaged at 33 degrees C (6 degrees C above the optimal 27 degrees C), resulting in little or no virus and protein production . As a result of these temperature-shift experiments, a larger-scale (14 1 air-lift bioreactor) serum-free culture of Sf-9 insect cells was conducted at constant temperature (27 degrees C) to produce recombinant protein (beta-galactosidase) . A cell density as high as 1 x 10(7) cells.ml-1, and a beta-gal concentration of up to 104,000 unit.ml-1 were achieved. Cytotechnology, 1992, 9(1-3), 11 - 9 An engineering analysis of rotating sieves for hybridoma cell retention in stirred tank bioreactors; Favre E et al.; The use of internal rotating sieves for perfused hybridoma culture offers unique advantages but has been up to now largely empirical . Calculations have been performed on a 15 l spinfilter stirred tank in order to have an idea of hydrodynamic conditions inside and outside the rotating sieve . The large peripheral velocity value, resulting from sieve rotation (compared to axial and radial velocities) is expected to affect strongly sieve surface colonization by cells; this is confirmed by lab scale experiments, showing that cell colonization is prevented providing sieve rotation exceeds a defined value (around 0.6 m.s.1 tip speed); the fluid removal force calculated under these conditions appears to be in the range of 10 pN, similar to the adhesion force already reported for mammalian cells attached to inorganic substrata. Cytotechnology, 1992, 8(3), 207 - 14 Determination of division rates of rCHO cells in high density and immobilized fermentation systems by flow cytometry; Borth N et al.; As most high density and immobilized fermentation systems do not allow the direct quantitative determination of cell density, two flow cytometric methods (the determination of incorporation of bromodeoxyuridine into newly synthesized DNA and the increase in mitotic cells by colchicine blockage) were evaluated as to their suitability to measure true division rates of cells in bioreactors . The BrdU method gave division rates identical to the growth rates measured by cell count, while the colchicine block method gave values that were lower and varied with the cell line . This is due to the cytotoxicity of colchicine and makes a calibration of the method for each cell line necessary . Both methods have been successfully used to measure division rates of rCHO cells immobilized in an alginate matrix as well as in macroporous carriers in a fluidised bed system and in dialysis culture. Cytotechnology, 1992, 8(3), 179 - 87 A comparison of simple growth vessels and a specially designed bioreactor for the cultivation of hybridoma cells; Persson B et al.; Three tank type bioreactors of very simple design were compared to a commercially available laboratory-scale bioreactor, designed especially for mammalian cell culture, for their ability to support hybridoma growth and antibody production under batch culture conditions . The comparison reveals quite similar numbers for maximum viable cell densities and IgG production, despite large differences in vessel and agitator geometry and aeration mode . Furthermore, some data indicate that the hydrodynamic stress level in the growth vessels may influence the specific production rate of the cells and thus the overall productivity of the reactors. Cytotechnology, 1992, 8(1), 85 - 8 High density culture of HeLa cells in a CelliGen perfusion system; Chen Y et al.; A hollow fiber cartridge may be used in an extraneous recycle loop to facilitate perfusion operation of a stirred tank bioreactor . Retention of cells while removing waste products and replenishment with fresh nutrients allows higher than normal cell densities obtained in batch or continuous culture systems . This system successfully propagated HeLa cells to over 11 million viable cells per milliliter . Much higher perfusion rates (up to 4 vessel volumes per day) were necessary for high density culture of HeLa cells compared to BHK or a hybridoma cell line because of a much higher specific cellular metabolic rate . Cell specific glucose consumption rate, lactate production and ammonia production rates are several times higher for HeLa cells . Reproducible high cell densities and viabilities can be repeatedly obtained after harvest and dilution of a HeLa cell culture by partial drainage and reconstitution in the bioreactor. Appl Microbiol Biotechnol, 1992 Jan, 36(4), 446 - 51 A model for penicillin production with and without temperature shift after the growth phase; Kluge M et al.; A strain of Penicillium chrysogenum producing about 8 milligrams/l of penicillin V, was cultivated in a 10-1 bioreactor . Under carbon (C)-limitation during the production phase a glucose/ammonium sulphate mixture was fed using microprocessor control . When the temperature was shifted from 25 degrees C to 30 degrees C at the end of the active growth phase, the specific penicillin production rate was increased by 30%, while the yield remained constant . Maximal productivity without sporulation was obtained when the net growth rate of the active (respiring and producing) biomass, estimated by measuring the respiration rate under defined conditions, was equal to or higher than 0.004 h-1 . A model was developed for penicillin fermentation during C-limitation possessing the following properties: (1) the model is based on ordinary differential equations; (2) the influence of different nutrients is considered; (3) the model recognizes two cell types (active and inactive); (4) the model describes the influence of a temperature shift at the end of the vigorous growth phase. J Biotechnol, 1992 Jan, 22(1-2), 51 - 68 Safety and economic aspects of continuous mammalian cell culture; Werner RG et al.; Mammalian cell cultures are the most appropriate host cells for recombinant DNA derived products if complex protein structures have to be synthesized in their native form . Due to their physiological behaviour they grow either adherent or in suspension . For the attachment of adherent cells, microcarriers or wire springs can be applied to increase the internal surface of the bioreactor . Both systems provide a simplified media exchange but, however, show some limitations in scale up . In contrast, suspension culture systems as homogeneous systems independent of any carrier have not shown any limitation in scale up . Because most cell lines which are of commercial interest grow in suspension, this technology is best advanced and used in batch and continuous mode . Although mammalian cell cultures are sensitive to hydrodynamic shear forces, technologies for deep tank production are developed which allow stirrer tip speed of up to 1.5 m s-1 sufficient for oxygen uptake, suspension of cells and homogeneous supply with nutrients . For long term bioprocesses without selection pressure it has to be considered that transformed cell lines might show genetic instability due to their variations of chromosomes . In addition, sterile technology becomes an important factor in long term bioprocesses . The decision as to which cell culture system should be chosen, whether batch or continuous processes should be applied essentially is based on the capital investment, the amount of material to be produced, genetic stability of the production cell line, reliability of sterile technology and the flexibility required in the production plant . Under the assumption that 20 kg of a protein have to be produced per year and the same product concentrations in the harvest fluid are reached in the batch process and for instance in the chemostat, it can be considered that the capital investment for one 10,000 l batch process and a 2 x 2,000 l continuous process, necessary to produce the amount of material, is comparable . Risk of microbial contamination or technical failure can be considered to be fairly low in the batch process . The economic risk for long term bioprocess in the chemostat can be expected to be medium and high in the perfusion system which is in the large scale not technically fully satisfactory . In addition, due to the longer down time period after contaminations and the start up of the continuous process, the annual yield of the batch process can be considered to be higher.(ABSTRACT TRUNCATED AT 400 WORDS) J Biotechnol, 1992 Jan, 22(1-2), 41 - 50 Effect of specific growth rates on productivity in continuous open and partial cell retention animal cell bioreactors; Robinson DK et al.; A clonal derivative of a transfectant of the SP2/0 myeloma cell line producing a chimeric monoclonal antibody was cultivated in both continuous open and continuous partially-closed bioreactors . Using an open system for the determination of kinetic parameters, we showed that the production of this chimeric mAb was growth associated . As such, the volumetric productivity increased linearly with increasing dilution rate up to the maximum dilution rate . Three continuous cultivations employing partial cell retention were conducted . In agreement with mathematical predictions, the product titer and volumetric productivity were independent of the degree of cell retention when the total dilution was held constant . When cells were maintained at a low specific growth rate, the product titer was independent of dilution rate and the volumetric productivity increased with increasing dilution rate, again in agreement with mathematical predictions . Since the partially-closed bioreactor could be operated at dilution rates in excess of the maximum specific cellular growth rate, volumetric productivities were greater than those achievable in the open bioreactor . However, when cells were maintained at a high specific growth rate, cell accumulation was limited and product titers decreased at high dilution rates . Therefore, the volumetric productivity in this latter case did not increase at higher dilution rates. J Biotechnol, 1992 Jan, 22(1-2), 31 - 40 Continuous hybridoma suspension cultures with and without cell retention: kinetics of growth, metabolism and product formation; Schmid G et al.; A laboratory scale bioreactor was constructed from glass and polycarbonate materials whereby a track-etch membrane (3 microns pore diameter) was integrated into its two-part bottom flange . The reactor performance was evaluated for continuous hybridoma suspension cultures under various conditions of cell retention . A total retention experiment demonstrated that this type of stirred tank reactor cannot be operated at near zero growth rate conditions . Instead, at steady viable cell concentrations of congruent to 3 x 10(6) cells per ml, specific growth and death rates were estimated at 0.60 +/- 0.06 d-1 . Specific substrate (glucose, glutamine, O2, amino acids) consumption, by-product (ammonia, alanine, amino acids) and product (antibody) production rates as well as various apparent molar yield coefficients were obtained and are compared to metabolic quotients and yield coefficients previously calculated from standard continuous culture experiments, i.e., without cell retention, at specific growth rates of 0.63 and 1.24 d-1 . Furthermore, steady-state data on viable cell and antibody concentrations, spec . mAb productivities, and space-time yields determined before and after a step change (2.5-fold increase) in dilution rate at identical specific growth rates mu are presented. J Biotechnol, 1992 Jan, 22(1-2), 153 - 69 Heat shock gene expression in continuous cultures of Escherichia coli; Heitzer A et al.; Temperature inducible systems for the controlled expression of recombinant genes are finding increasing industrial applications . These involve either short or long term exposure of the process culture to superoptimum temperatures . It is well known that bacteria respond to a sudden increase in their environmental temperature with an immediate transient increase in the synthesis rates of specific heat shock proteins . The use of continuous flow processes for the production of recombinant proteins would allow higher productivity and smaller scale bioreactors . However, the induction patterns of heat shock proteins in continuous culture after defined heat shocks are not well defined despite a large amount of information which is now available concerning heat shock protein induction in batch cultures . An overview of this information is presented to enable a better understanding of the response in continuous cultures . The latter was investigated by monitoring the transient expression of a representative heat shock gene, htpG, in E . coli in continuous culture . The relative magnitude of the response was found to be both temperature and exposure time dependent, but growth rate independent . Changing medium composition resulted in both different steady and transient state expression levels. Enzyme Microb Technol, 1992 Jan, 14(1), 58 - 63 Controlling and predicting monoclonal antibody production in hollow-fiber bioreactors; Handa-Corrigan A et al.; A simple optimization strategy is described which enables monoclonal antibody (MCA) production in hollow-fiber bioreactors to be controlled and predicted . The MCA production rate is demonstrated to increase linearly with the uptake rates of glucose and glutamine and with the production rates of lactate and ammonia . The uptake and production rates of these metabolites can, in turn, be predicted from the pumping rates of basal medium to the bioreactor . We recommend a period of 2 weeks at the start of the cultivation when intensive assaying and monitoring should be carried out . After this period, the medium flow rate and MCA production rate may be predicted by linear extrapolation. Chirurgie, 1992, 118(10), 672 - 7 {Extracorporeal bio-artificial liver using isolated hepatocytes . An experimental study in the rat}; Fremond B et al.; A new type of bioartificial liver using isolated hepatocytes immobilized in alginate beads was developed and its capacity of correcting the metabolic deficiency of bilirubin conjugation in Gunn rats was assessed . Hepatocytes were isolated from Sprague-Dawley rats using the in situ collagenase perfusion technique, and they were then immobilized in Calcium alginate beads . The capacity of these immobilized hepatocytes to conjugate in vitro bilirubin was checked as compared to monolayer hepatocyte culture . The bioartificial liver consisted in a cylindrical bioreactor containing either alginate beads and hepatocytes (test group), or only alginate beads (control group) . Gunn rats were connected to this bioreactor through and extracorporeal circulation system, and "bile samples were collected" every hour . Bilirubin mono and biconjugates were dosed in the bile using the high-performance liquid chromatography technique . The viability of alginate immobilized hepatocytes, determined before and after each experiment, was stable at 75% . In the test group, the total conjugate concentration rapidly increased to reach a maximum value of 204 +/- 16 microns after 3 hours, while in the control group, there were only conjugate traces (1 micron) . These results show that the bioartificial liver is an efficient means to temporarily correct genetic deficiency in Gunn rats . Such a system could be of therapeutic interest in case of acute hepatic insufficiency. Asia Pac J Public Health, 1992-93, 6(2), 40 - 5 Environmental biotechnology: biotechnology solutions for a global environmental problem, hazardous chemical wastes; Omenn GS; Biotechnology has a growing place in the remediation of hazardous waste sites throughout the world, and especially in Asia where population density is high and land and fresh water are scarce . In-situ bioremediation has been demonstrated already to be highly effective for petroleum hydrocarbons (alkanes, aromatics, polychlorophenols) and organophosphate pesticides in soils and for gasoline by-products (benzene, toluene, xylene) and chlorinated solvents (trichloroethylene) in groundwater . Heavy metals and PCBs are not suitable for bioremediation . Environmental biotechnology includes solid-phase and slurry-phase bioremediation for contaminated soils and site-specific bioreactors for contaminated groundwater . Specific examples are presented . From a policy point of view, accumulated wastes must be detoxified, preferably at sites where they already exist . We cannot continue to rely on their removal and disposal "elsewhere" . For current waste streams, we must minimize the volumes and toxicity . Environmental biotechnology will play a key role. Chin J Biotechnol, 1992, 8(2), 123 - 30 Mass culture of anchorage-dependent animal cells with newly born calf skin collagen membrane and microcarrier; Chen Y et al.; It was shown that collagen substrate enhances the growth as well as the differentiation of many cells in culture . Collagen is one of the major fibrous proteins of animal bodies and the pure collagen used in this experiment was extracted from the newly born calf skin by chemical and biochemical methods . The analytical results obtained by ion-exchange chromatography and electrophoresis showed that the main components of denatured collagen were alpha monomers and beta dimers . The collagen and denatured collagen membranes were prepared by coating their solution on peteri dishes . Various types of cells were cultured on these membranes after being irradiated by ultraviolet ray . The denatured collagen was proved a good substratum for culturing anchorage dependent cells . A denatured collagen (gelatin) microcarrier, GT-2 was obtained by cross-linking gelatin with glutaraldehyde in a suspension polymerization process . These microcarriers were used successfully to culture various anchorage-dependent cells such as Vero, CHO, Bowes and fish cells in varying scales, including T-flasks, spinning bottles, revolving bottles and 1.5 l and 20 l bioreactors. Chin J Biotechnol, 1992, 8(3), 179 - 86 A perfusion system for high productivity of monoclonal antibody by hybridoma cells in a CelliGen bioreactor; Chen Y; DA4-4 (ATCC HB57) is a shear sensitive mouse-mouse hybridoma cell, producing an IgG1 monoclonal antibody against human IgM . It was grown successfully in a perfusion propagation system consisting of a 1.5 CelliGen stirred bioreactor and a hollow fiber cartridge . CelliGen system produced low shear force and cells could grow well at high agitation of 150 rpm . The culture was maintained for 40 days and cell number reached 20 x 10(6)/ml . Maximal monoclonal antibody concentration was 4.75 mg/ml . This system produced about 1.0 g of antibody every day at its peaks. Biosens Bioelectron, 1992, 7(9), 631 - 5 Implementation of a thermal biosensor in a process environment: on-line monitoring of penicillin V in production-scale fermentations; Rank M et al.; The production of penicillin V was monitored in 0.5 m3 and 160 m3 bioreactors . The thermal biosensor was an enzyme thermistor modified for split-flow analysis . The heat signal generated in the enzyme column was corrected for any nonspecific heat with the use of an identical but inactive reference column . The on-line monitoring was performed in the fermentation pilot plant and in a fermentation plant of Novo Nordisk A/S . Immobilized beta-lactamase was used to monitor three consecutive 0.5 m3 penicillin fermentations . Broth samples were continuously filtered through a tangential flow filtration unit in a sterile external loop . The on-line penicillin V values were 10% higher than those obtained by off-line HPLC analysis . Alternatively a polypropylene filtration probe was inserted into a 160 m3 bioreactor and samples were withdrawn at 0.5 ml/min . The same experiments were repeated with purified and immobilized penicillin V acylase . The on-line penicillin V values obtained with this enzyme correlated very well with those from HPLC analysis . The on-line monitoring was controlled and analysed by a software program written in Labtech Notebook. Immunol Res, 1992, 11(3-4), 181 - 90 Murine soluble Fc gamma receptors/IgG-binding factors (IgG-BF): analysis of the relation to Fc gamma RII and production of milligram quantities of biologically active recombinant IgG-BF; Sautes C et al.; The production of soluble forms of low-affinity Fc gamma R by cells expressing recombinant or natural membrane Fc gamma RII, and the structural relationships between these soluble receptors and membrane Fc gamma RII are described . We show that 37-40 kD soluble Fc gamma RII, corresponding to the two N-terminal domains of Fc gamma RII and binding to IgG, are spontaneously produced in vitro by cleavage of membrane Fc gamma RII . Moreover, we describe methods to produce and purify to homogeneity large quantities of endotoxin-free recombinant IgG-binding factor (rIgG-BF) from the culture medium of a cell line transfected with a mutated Fc gamma RII cDNA . These methods include the use of bioreactors for culturing transfected fibroblasts and the purification of rIgG-BF by ion-exchange chromatography and hydrophobic-interaction chromatography . By using such procedures, about 2.4 mg of rIgG-BF were purified from 1 liter of culture medium of transfected fibroblasts . Like natural IgG-BF, the 95-99% pure rIgG-BF suppressed, in a dose-dependent manner, secondary in vitro IgG antibody responses to sheep red blood cells. Ann N Y Acad Sci, 1991 Dec 27, 646, 322 - 33 Integration of cell culture with continuous, on-line sterile downstream processing; Grandics P et al.; The development of an integrated system for the continuous, automated production of pure cell culture derived proteins is discussed . The system comprises a cell culture subunit for the continuous culture of mammalian cells and a purification subunit linked on-line to the cell culture subunit . The cells are compartmentalized and continuously perfused with culture medium . The cell culture medium leaving the bioreactor is perfused through a sterile immunoaffinity column that instantaneously removes the product from the culture fluid . This results in improved product quality because the product is quickly removed from the cell culture, thus minimizing contact with degradative enzymes . The culture medium, stripped from the secreted product, is recirculated into the bioreactor . The system allows simple, automated, and economical production of purified proteins with higher quality than that possible with current production methods . The integration also allows on-line, real-time process monitoring, thus simplifying process development and allowing more consistent production of biologics. Ann N Y Acad Sci, 1991 Dec 27, 646, 300 - 6 High cell density fermentation of recombinant Escherichia coli with computer-controlled optimal growth rate; Knorre WA et al.; In recent years recombinant DNA technology has enabled us to produce various proteins of therapeutic importance with microorganisms . As an appropriate host organism, E . coli plays a dominant role . Yields of E . coli dry cell mass in shaker flask culture range from 1-2 g/L, whereas in fermentors up to 10 g dry cells/L can be achieved . ZIMET and GBF have developed a high cell density fermentation process that produces E . coli (on a glucose/mineral salt medium) up to more than 100 g dry cells/L in a special fed-batch mode . This cultivation strategy prevents oxygen limitation and hence the accumulation of acetate and other metabolic byproducts . The specific growth rate can be adjusted so that product formation reaches its optimum value . An example of the production of alpha1-interferon is presented . The high cell density fermentations were realized in 30- and 450-L Chemap fermentors (ZIMET) and in a three-stage bioreactor scale-up system (72, 300, and 1,500 L) developed in cooperation with GBF and B . Braun Melsungen AG . Multiloop controllers were used to control the process variables. Appl Biochem Biotechnol, 1991 Dec, 31(3), 283 - 310 Review and patents and literature . The use of insect cell cultures for recombinant protein synthesis: Engineering aspects; Murhammer DW; The use of the insect cell/baculovirus expression system for producing recombinant proteins of bacterial, plant, insect, and mammalian origin has become widespread . The popularity of this eukaryotic expression system is due to many factors, including (1) potentially high protein expression levels, (2) ease and speed of genetic engineering, (3) ability to accommodate large DNA inserts, (4) protein processing similar to higher eukaryotic cells (e.g., mammalia cells), and (5) ease of insect cell growth (e.g., suspension growth) . The following review of the literature discusses two engineering aspects of recombinant protein synthesis by insect cell cultures: bioreactor scale-up and insect cell line selection . Following this review patent abstracts and additional literature pertaining to expression of recombinant proteins in insect cell culture are listed. Biotechniques . 1991 Dec;11(6):702, 704, 706. Culture of eukaryotic cells with macro-reticulate buffers: fermentation of cellulolytic fungi; Pompei R et al.; Fermentation of fungi for large-scale production of extracellular cellulolytic enzymes requires a strict control of pH . At the lab scale, where bioreactors are not available, a culture in the exponential growth phase requires frequent manual pH adjustments . When fungi are grown in the presence of macroreticulate buffers, the culture is stable and does not require any pH control for as long as two weeks . These insoluble buffers are polyacrylamide beads (e.g., 10%T, 8%C) containing acrylamido weak acids and bases in such ratios as to unequivocally define a single pH value along the pH sale . At such pH, the macroreticulate buffers possess a strong buffering power (up to 100 milliequivalent liter-1 pH-1) . In the present example, a Trichoderma sp . strain is grown in the presence of 12% beads (v/v) with an isoelectric point of 5.6, containing 100 mM of a pK 6.2 weak acrylamido base and 89 mM of a pK 4.6 weak acrylamido acid . Enzyme production (exoglucanase, endoglucanase, xylanase, beta-glucosidase) is as good as (and often better than) the control in which the pH is adjusted manually 2-3 times/day. Artif Organs, 1991 Dec, 15(6), 474 - 80 Encapsulated multicellular spheroids of rat hepatocytes produce albumin and urea in a spouted bed circulating culture system; Takabatake H et al.; Multicellular spheroids are spherical cell-aggregates that retain tridimensional architecture and tissue-specific functions . For use of multicellular spheroids of hepatocytes in a bioreactor for hybrid artificial liver support, we studied the effect of encapsulation and circulating culture on their integrity and tissue-specific functions . Multicellular spheroids of rat hepatocytes were encapsulated into microdroplets of calcium alginate gel and were used as a bioreactor in medium circulating in a spouted bed chamber . Approximately 10% of the hepatocytes of an adult rat were entrapped in a bioreactor chamber, connected to a gas exchanger and a medium reservoir . The total bed volume of the system was 250 ml . The pH and DO2 of the hormonally defined circulating medium was maintained constantly . Albumin and urea were produced in a linear fashion for 64 h at the rates of 0.02 micrograms/microgram cell protein/day and 0.15-0.2 ng/micrograms cell protein/day, respectively . Viability and structural stability of the spheroids were well preserved after the culture period . These results indicate that these encapsulated multicellular hepatocyte spheroids will provide a useful bioreactor for the continuous production of albumin, in vitro and also a prototype hybrid artificial liver support. Appl Microbiol Biotechnol, 1991 Dec, 36(3), 324 - 6 High albumin production by multicellular spheroids of adult rat hepatocytes formed in the pores of polyurethane foam; Matsushita T et al.; Adult rat hepatocytes formed spherical multicellular aggregates (spheroids) when they were cultured in the pores of polyurethane foam (PUF) . The diameter of the spheroids was within the range 100-200 microns . These spheroids partly attached and immobilized in the PUF pores for at least 2 weeks . The albumin production rate by the spheroids increased up to 17.0 micrograms/10(6) nuclei per day during the first 6 days and maintained at a high level for 2 weeks . In contrast, the albumin production rate by the monolayer markedly decreased after 3 days . The spheroid culture using PUF seems to be a convenient and simple method for maintaining some differentiated functions of hepatocytes and for making a bioreactor using the function of spheroids. Trends Biotechnol, 1991 Dec, 9(12), 427 - 37 Fluid-mechanical damage of animal cells in bioreactors; Papoutsakis ET; The fluid-mechanical and some biological aspects of damage to animal cells in bioreactors due to agitation and/or aeration are attracting renewed attention . In microcarrier bioreactors, cell damage is due to forces generated by the interaction of microcarrier beads with each other and also with small turbulent eddies . For freely suspended cells grown in mixed bioreactors, cell damage is most frequently due to bubble breakup or fast-draining liquid films around rearranging gas-liquid interfaces. Appl Microbiol Biotechnol, 1991 Nov, 36(2), 208 - 10 A novel micromanipulation technique for measuring the bursting strength of single mammalian cells; Zhang Z et al.; Information about the bursting strength of animal cells is essential if the mechanisms of cell damage in bioreactors are to be understood, and if cell mechanical properties are ever to be related to cell structure and physiology . We have developed a novel cell compression technique that makes it possible to directly measure the bursting strength of single mammalian cells, and to infer information about cell mechanical properties. Enzyme Microb Technol, 1991 Nov, 13(11), 913 - 9 Biological responses of hybridoma cells to hydrodynamic shear in an agitated bioreactor; Abu-Reesh I et al.; Effects of long-term hydrodynamic shear on hybridoma cells were investigated in a 250-ml continuous stirred-tank reactor (CSTR) . Cells grown at steady state were subjected to step changes in agitation rates . Cell viability, glucose consumption, and monoclonal antibody (MAb) production were determined at high agitation rates and compared with the control (100 rev min-1) . Impeller tip speeds higher than 40 cm s-1 caused a significant drop in cell concentration and respiration activity, and increased lactate dehydrogenase (LDH) release to the culture medium . Also, high agitation speeds caused a decrease in MAb concentration and an increase in specific glucose consumption rate . The effects of dilution rate and serum concentration on the sensitivity of hybridoma cells to hydrodynamic shear were determined . Serum was found to protect the cells against shear damage and had a significant positive effect on hybridoma growth and MAb production . Shear damage on cells in CSTR was approximated to first-order kinetics . The death rate constant increased sharply at impeller tip speeds above 40 cm s-1. Enzyme Microb Technol, 1991 Nov, 13(11), 882 - 92 Large-scale (20 l) culture of surface-immobilized Catharanthus roseus cells; Archambault J; Surface-immobilized C . roseus cell cultures were grown in a 20-l modified airlift bioreactor operated at 0.51 vvm (kLa approximately 8 h-1) under various gassing regimes {air, 2% (v/v) and 5% CO2} . Extracellular ammonium, phosphate, and nitrate ions as well as carbohydrate uptake and pH value of the medium were monitored together with on-line dissolved oxygen concentration, conductivity of the medium, and carbon dioxide production rate (CPR) of the cultures . Cultures supplemented with 2% CO2 showed higher nitrate (5.0-7.0 mM d-1) and carbohydrate (3.3 g l-1 d-1) uptake rates and biomass production (mu approximately 0.24 d-1, yield approximately 0.33 g dw g CHO-1 and 7.4 g dw L-1) as compared to air (3.6 mM d-1, 2.1 g l-1 d-1; 0.20 d-1, 0.25 g dw g CHO-1 and 5 g dw l-1) and 5% CO2 (2.0-3.6 mM d-1, 2.0 g l-1 d-1; 0.11 d-1, 0.20 g dw g CHO-1 and 5 g dw l-1) cultures and as reported previously for suspension cultures . In addition, air and 5% CO2 cultures displayed incomplete carbohydrate uptake and, more important, phosphate and ammonium ion release into the medium at the end, which was ascribed to loss of viability . This was not observed for 2% CO2 immobilized bioreactor as well as shake flask control suspension cultures, which suggests that sparged C . roseus surface-immobilized cell cultures require 2% CO2 supplementation of the gas phase for both maximum growth and retained viability . The maximum CPRs of all cultures were in the same range (2.1-2.8 mM CO2 l-1 h-1) . However, the estimated maximum specific CO2 production rates of 2% CO2 and 5% CO2 immobilized cultures (0.6 mM g dw-1 h-1) were lower than those found for air-sparged immobilized cultures (1.0-1.3 mM g dw-1 h-1) . These rates are significantly higher than those reported in the literature for C . roseus cell suspension cultures performed in bioreactors gassed with air (approximately 0.2-0.55 mM g dw-1 h-1). Enzyme Microb Technol, 1991 Nov, 13(11), 873 - 81 Metabolism of hybridoma cells and antibody secretion at high cell densities in dialysis tubing; Kasehagen C et al.; The experimental setup, consisting of a bundle of dialysis tubing 2.5 mm in diameter {10-15 kD cutoff, mean pore size 25 A, 20 microns (dry) and 40 microns (wet) wall thickness} inserted into a 1-l glass bioreactor supplied with oxygen and pH electrodes, a porous gas distributor, a sampling tube, and a holder for the eight pieces of dialysis tubing, was developed to investigate the properties and the microenvironment of hybridoma cells enclosed in the tubing during their batch cultivation . The concentrations of low-molecular-weight medium components were the same inside and outside the tubing, and it was possible to control the microenvironment of the cells in the tubing easily . The cell damage caused by mechanical stress was less in the dialysis tubing than in stirred spinner flasks . The influence of the initial cell density in the range from 4 X 10(5) to 1 X 10(8) cells ml-1 and the cultivation time were evaluated according to the total and viable cell concentrations and the cell/cell fragment size distributions . Furthermore, the cell membrane properties, glucose consumption rate, lactate, ammonia and lipid storage material, and the monoclonal antibody production rates as well as intracellular enzyme activities in the culture medium were measured and compared to those in reference cultures in spinner flasks with the same inoculum at low initial cell densities . In dialysis tubing in a concentration range of 5 X 10(6) to 10(8) cells ml-1, the total and viable concentrations of cells remained the same during cultivation.(ABSTRACT TRUNCATED AT 250 WORDS) Biotechnol Prog, 1991 Nov-Dec, 7(6), 481 - 94 Growth, metabolic, and antibody production kinetics of hybridoma cell culture: 2 . Effects of serum concentration, dissolved oxygen concentration, and medium pH in a batch reactor; Ozturk SS et al.; The effects of serum, dissolved oxygen (DO) concentration, and medium pH on hybridoma cell physiology were examined in a controlled batch bioreactor using a murine hybridoma cell line (167.4G5.3) . The effect of serum was also studied for a second murine hybridoma cell line (S3H5/gamma 2bA) . Cell growth, viability, cell density, carbohydrate and amino acid metabolism, respiration and energy production rates, and antibody production rates were studied . Cell growth was enhanced and cell death was decreased by increasing the serum level . The growth rates followed a Monod-type model with serum being the limiting component . Specific glucose, glutamine, and oxygen uptake rates and specific lactate and ammonia production rates did not change with serum concentrations . Amino acid metabolism was slightly influenced by the serum level . Cell growth rates were not influenced by DO between 20% and 80% air saturation, while the specific death rates were lowest at 20-50% air saturation . Glucose and glutamine uptake rates increased at DO above 10% and below 5% air saturation . Cell growth rate was optimal at pH 7.2 . Glucose and glutamine uptake rates, as well as lactate and ammonia production rates, increased above pH 7.2 . Metabolic rates for glutamine and ammonia were also higher below pH 7.2 . The consumption or production rates of amino acids followed the glutamine consumption very closely . Cell-specific oxygen uptake rate was insensitive to the levels of serum, DO, and pH . Theoretical calculations based on experimentally determined uptake rates indicated that the ATP production rates did not change significantly with serum and DO while it increased continually with increasing pH . The oxidative phosphorylation accounted for about 60% of total energy production . This contribution, however, increased at low pH values to 76% . The specific antibody production rate was not growth associated and was independent of serum and DO concentrations and medium pH above 7.20 . A 2-fold increase in specific antibody production rates was observed at pH values below 7.2 . Higher concentrations of antibody were obtained at high serum levels, between 20% and 40% DO, and at pH 7.20 due to higher viable cell numbers obtained. Biotechnol Prog, 1991 Nov-Dec, 7(6), 471 - 80 Growth, metabolic, and antibody production kinetics of hybridoma cell culture: 1 . Analysis of data from controlled batch reactors; Ozturk SS et al.; A mouse-mouse hybridoma cell line (167.4G5.3) was cultivated in a 1.5-L stirred-tank bioreactor under constant pH and dissolved oxygen concentration . The transient kinetics of cell growth, metabolism, and antibody production were followed by biochemical and flow cytometric methods . The cell-specific kinetic parameters (growth and metabolic rates) as well as cell size were constant throughout the exponential phase . Intracellular protein and RNA content followed a similar trend . Cell growth stopped when the glutamine in the medium was depleted . Glucose could not substitute for glutamine, as glucose consumption ceased after glutamine depletion . Ammonia and lactate production followed closely glutamine and glucose consumption, respectively . Alanine, glutamate, serine, and glycine were produced but other amino acids were consumed . The cells are estimated to obtain about 45% of the total energy from glycolysis, with the balance of the metabolic energy provided by oxidative phosphorylation . The antibody was produced at a constant rate in both the exponential and decline phases of growth . The intracellular antibody content of the cells remained relatively constant during the exponential phase of growth and decreased slightly afterwards. J Biotechnol, 1991 Nov, 21(1-2), 173 - 85 Enzyme sensor-FIA-system for on-line monitoring of glucose, lactate and glutamine in animal cell cultures; Renneberg R et al.; Enzyme sensors for glucose, lactate and glutamine were connected via flow-injection analysis (FIA) devices to two different bioprocesses . They were used for on-line process control of perfused bioreactor systems containing mammalian cell lines producing a monoclonal antibody and recombinant interleukin-2 . The biosensor system gives direct access to important process data which can be used as control parameters for long term cell cultivation systems. Biotechnology (N Y), 1991 Nov, 9(11), 1100 - 2 Modular integrated fluidized bed bioreactor technology; Reiter M et al.; We describe the design and demonstrate the application of a modular integrated fluidized bed bioreactor system . Basically the system is a reactor vessel equipped with an extending cylinder and a liquid distributor plate . Instead of an external recirculation loop, as used in existing fluidized bed systems, a low shear stress impeller is used as the recirculation pump . The system has several unique features, such as modular exchangeable elements, efficient oxygenation and the option of operating as a stirred tank-, a packed bed- or a fluidized bed reactor . An example of a fluidized bed run using CHO-K1 cells is shown . Under standard culture conditions a 100-fold increase in cell density (up to 1.2 x 10(8) cells/ml) was achieved. Glycoconj J, 1991 Oct, 8(5), 414 - 23 Structural studies of gangliosides from the YAC-1 mouse lymphoma cell line by immunological detection and fast atom bombardment mass spectrometry; Muthing J et al.; YAC-1 cells were propagated in bioreactors in 1 l and 7.5 l volumes . The cells were metabolically labelled with D-{1-14C}galactose and D-{1-14C}glucosamine . The ganglioside fraction, purified by DEAE-Sepharose and silica gel column chromatography, showed on thin layer chromatography four major bands with mobilities between GM1 and GD1a . Gangliosides, obtained by further purification steps including high performance liquid chromatography on silica gel 60 columns with a gradient system of isopropanol:hexane:water, and preparative high performance TLC were characterized by (1) immunostaining of corresponding asialogangliosides obtained by mild acid hydrolysis and neuraminidase treatment and (2) fast atom bombardment mass spectrometry of native and permethylated samples and methylation analysis of GM1b ganglioside . As well as small amounts of GM2 and GM1, the major gangliosides found in the complex mixture were GM1b and GalNAc-GM1b . The structural heterogeneity of these gangliosides was caused by (a) substitution of the ceramide moiety by fatty acids of different chain length and degree of unsaturation (C16:0, C24:0, C24:1) and (b) N-substitution of the sialic acid moieties with either acetyl or glycolyl groups . Disialogangliosides were detected only in low amounts and will be the subject of further investigation . A polyclonal chicken antiserum was raised against IVNeuAc-GgOse5Cer . The antiserum was highly specific for gangliosides (IVNeuAc and IVNeuGc) and asialogangliosides with a GgOse5Cer backbone . No cross-reaction with GM1b or GgOse4Cer was observed. Antonie Van Leeuwenhoek, 1991 Oct-Nov, 60(3-4), 133 - 43 Quantitation of microbial metabolism; Sonnleitner B; Quantitation is a characteristic property of natural sciences and technologies and is the background for all kinetic and dynamic studies of microbial life . This presentation concentrates therefore on materials and methods as tools necessary to accomplish a sound, quantitative and mechanistic understanding of metabolism . Mathematical models are the software, bioreactors, actuators and analytical equipment are the hardware used . Experiments must be designed and performed in accordance with the relaxation times of the biosystem investigated; some of the respective consequences are discussed and commented in detail . Special emphasis is given to the required density, accuracy and reproducibility of data as well as their validation. Cytotechnology, 1991 Oct, 7(2), 63 - 74 The medium cycle bioreactor (MCB): monoclonal antibody production in a new economic production system; Kempken R et al.; The perfusion mode of a continuous cell culture bioreactor was modified to establish a closed loop system . Eighty percent of the spent medium was re-used twice . The medium cycle bioreactor unit was operated sterile and uncomplicated without a technical retention system for the high molecular weight substances . Therefore, only 20% of the actual medium was necessary to run the recycling process . During seven days culture time in a two liter scale 5 grams of IgG1 type monoclonal antibody was produced . During that period the cell specific productivity was constant . Renewal of proteins was omitted because the protein content in the system persisted at a high level . Therefore, self-conditioning substances of the cells were retained in the system as well as the expensive medium components (proteins with catalytic or stimulating function) . Seventy to 80% of medium costs and medium quantity were saved for each medium recycling step . Only cheap metabolites that are consumed by the cells had to be supplemented . Uptake rates of glucose and amino acids were calculated to establish a suitable supplementation mixture for the recirculated medium. Enzyme Microb Technol, 1991 Oct, 13(10), 822 - 7 Use of a stationary bed reactor and serum-free medium for the production of recombinant proteins in insect cells; Kompier R et al.; Insect cells (Spodoptera frugiperda) have been cultured in a stationary bed reactor, packed with a fibrous polyester carrier . When the bioreactor was perfused with serum-supplemented medium, a cell density of 6 x 10(6) cells ml-1 packed carrier was reached . Scanning electron microscopy investigations have shown that the insect cells grew along the three-dimensionally oriented fibers of the Fibra-cel carrier . After infection of the logarithmically growing cells with a recombinant baculovirus (Autographa californica) containing the gene coding for beta-galactosidase, the medium in the bioreactor was changed to serum-free medium . At day 13 postinfection (p.i.), a beta-galactosidase level of 320 microgram ml-1 and, at day 17 p.i., a virus titer of 2.1 x 10(8) TCID50 units ml-1 (day 17 p.i.) were reached . In another bioreactor, operated in a similar way but with serum-containing medium, a beta-galactosidase concentration of 360 microgram ml-1 and a virus titer of 2.3 x 10(8) TCID50 units ml-1 were obtained . These results indicate the potential use of this production system for the production of recombinant protein and baculovirus in insect cells. J Biotechnol, 1991 Oct, 20(3), 249 - 61 Monitoring of the production of monoclonal antibodies by hybridomas . Part II: Characterization and purification of acid proteases present in cell culture supernatant; van Erp R et al.; An acid proteolytic activity has been found in cell culture supernatants from long-term cultivations of hybridoma cells in hollow fibre bioreactors using serum free medium . The proteolytic activity has now been further characterized and the main results were: (1) the proteolytic activity showed a maximum around pH 3 and declined essentially to zero at pH 8; (2) the activity was specifically inhibited by pepstatin A; (3) the acid proteases consisted of two sets of closely spaced bands with apparent molecular weights of 40-45K and 90-105K, respectively; (4) the protease bands (40-45K and 90-105K) were reactive with anti-human cathepsin D; (5) the IEP values of the acid proteases ranged from pH 4.55-6.5 . Furthermore, IgG incubation with the acid proteases isolated from hybridoma cells yielded fragments similar to those found in serum-free hollow fibre cell culture supernatants . These results indicated that the IgG fragments are the result of degradation by cathepsin D like proteases released after cell death or cell lysis. J Biotechnol, 1991 Oct, 20(3), 235 - 48 Monitoring of the production of monoclonal antibodies by hybridomas . Part I: Long-term cultivation in hollow fibre bioreactors using serum-free medium; van Erp R et al.; The long-term cultivation of hybridoma cells in hollow fibre bioreactors using serum-free medium, was monitored with respect to quantitative and qualitative aspects of the produced mAbs, cell viability, LDH and proteolytic activity . During the culture periods of hybridoma cells producing mAb OT-1C and 3A, the mAb concentration showed a decreasing trend with a concomitant increase of IgG fragments . The major IgG fragments did not bind the antigen and the molecular weights were significantly different from the corresponding IgG heavy and light chains . In addition, a good correlation was found between cell lysis, the presence of acid protease(s) and IgG fragments . The physicochemical and immunochemical properties of the "intact" mAbs (such as molecular weights, IEF patterns and affinity) did not change significantly during the culture period. Anal Chem, 1991 Sep 15, 63(18), 1906 - 9 Operation of ion-selective electrode detectors in the sub-Nernstian/linear response range: application to flow-injection/enzymatic determination of L-glutamine in bioreactor media; Matuszewski W et al.; A novel approach for eliminating positive errors from endogenous ionic interferences when using ion-selective electrodes as detectors in flow-injection enzyme-based blosensing configurations is described . The method involves using a high background level of interfering ions in the sample diluent/carrier stream to convert the normally logarithmic potentiometric sensor into a linear detector over a given concentration range of primary ions . A split-stream single-detector arrangement provides a convenient means to compensate for varying levels of background interferent ions in the injected samples . One portion of the split stream passes directly to the ion-electrode detector, yielding a signal linearly related to the concentration of endogenous primary ions in the sample . The second portion of the split sample is delayed while passing through an immobilized enzyme that generates electrode detectable primary ions in proportion to the concentration of the substrate analyte in the sample . Two linear equations with two unknowns describe the twin potentiometric responses observed . The concept is demonstrated by the accurate determination of L-glutamine in hybridoma bioreactor media via the use of an ammonium-ion-selective membrane electrode detector and immobilized glutaminase enzyme. Cytotechnology, 1991 Sep, 7(1), 33 - 8 Hybridoma growth and monoclonal antibody production in iron-rich protein-free medium: effect of nutrient concentration; Franek F et al.; The iron-rich (500 microM ferric citrate) protein-free supplement was added to six different basal media . Cell growth and monoclonal antibody production of a mouse-mouse hybridoma were investigated in 1.3 1 batch cultures performed in a laboratory bioreactor with automatic control of pH and dissolved oxygen concentration . RPMI 1640 served as the control medium . Fortification of the basal medium by balanced mixtures of amino acids and vitamins showed higher positive effect than daily supplementation by glucose and glutamine . Strongly fortified medium, based on RPMI 1640, was found superior to other basal media . The viability index increased by a factor of 3.04 and the total antibody production by a factor of 2.82, relative to the control. Biotechnol Appl Biochem, 1991 Aug, 14(1), 60 - 8 Human red blood cells as bioreactors for the inactivation of harmful xenobiotics; Fazi A et al.; Human red blood cells are able to inactivate lipophilic electrophiles by conjugation with reduced glutathione . This metabolic ability was found to be limited by the rate of permeation of the xenobiotic into erythrocytes and by the amount of available reduced glutathione . By a procedure of hypotonic dialysis, isotonic resealing and reannealing human red blood cells were overloaded with increasing amounts of reduced glutathione up to three- to fourfold the normal level without modification of their metabolic functions or of their energetic state . These overloaded erythrocytes were able to conjugate increasing amounts of xenobiotics and to export the resulting conjugates from the cells . These properties of glutathione overloaded erythrocytes are significant for the use of carrier erythrocytes in cases of acute intoxication by lipophilic electrophiles. Virology, 1991 Aug, 183(2), 739 - 46 Detection and analysis of Autographa californica nuclear polyhedrosis virus mutants with defective interfering properties; Kool M et al.; Defective interfering particles (DIPs) were generated upon continuous production of Autographa californica nuclear polyhedrosis virus (AcNPV) in bioreactors . This configuration mimicked the serial undiluted passaging of virus, which is known to result in plaque-morphology mutants . Restriction enzyme analysis of DIP-containing preparations of extracellular virus showed the presence of many DNA fragments in less than equimolar amounts . These fragments were colinear on the physical map of AcNPV and extended from map position 1.7 to 45 . These DIPs thus lacked 43% of the genetic information of the standard virus, including the polyhedrin and DNA polymerase genes . The existence of DIPs was confirmed by electron microscopy, where virions were observed with reduced length . Among the less than equimolar fragments in DIP-containing preparations, fragments were observed linking sequences from map positions 1.7 and 45 via a TGTT linker of unknown origin . The DIPs could not be plaque-purified and needed standard (helper) virus to replicate; DIP-containing preparations interfered with standard virus replication in an interference assay, which explained the reduction in productivity of an AcNPV expression vector-insect cell system in continuous bioreactor operations . The origin of these DIPs and their possible generation mechanism are discussed. Trends Biotechnol, 1991 Aug, 9(8), 279 - 84 Strategies for improving plasmid stability in genetically modified bacteria in bioreactors; Kumar PK et al.; Exploitation of recombinant organisms for the large-scale, commercial production of foreign proteins is often hampered by the problem of plasmid instability . A wide range of strategies have been reported for improving the stability of recombinant organisms . A combination of manipulating both the genetic design of recombinants and the conditions of culturing the organisms may be used to achieve stable host-vector associations during culture of recombinant organisms in bioreactors. ASAIO Trans, 1991 Jul-Sep, 37(3), M337 - 8 A hybrid artificial liver system . Function of cultured monolayer pig hepatocytes in plasma from hepatic failure patients; Uchino J et al.; To produce a new hybrid artificial liver system, cultured pig hepatocytes were used in this study . Hepatocytes from normal healthy pigs were cultured in multiwell dishes . From the third day of cultivation, hepatocytes were divided into three groups according to the media used (Group 1, L-15; Group 2, normal human plasma; Group 3, plasma from hepatic failure {HF} patients) . Measurements of cellular function of the cultured pig hepatocytes included metabolic activity (gluconeogenesis and ureogenesis), DNA content, and amino acid changes in the plasma . The ability to provide gluconeogenesis and ureogenesis by the cultured hepatocytes in HF plasma was maintained for 3 days, equal to that observed in Groups 1 and 2 . DNA content was no different in the three groups . Elevated amino acid levels in the HF plasma, Phe, Met, Lys, and Gly, were significantly reduced by the cultured hepatocytes . The results indicate that the use of primary cultured pig hepatocytes is a step toward a hybrid artificial liver system, and a promising candidate as a bioreactor. Appl Microbiol Biotechnol, 1991 Jul, 35(4), 440 - 6 Immobilization of microsomes into alginate beads is a convenient method for producing glucuronides from drugs; Haumont M et al.; The production of glucuronides from drugs by immobilized microsomal uridine diphosphate (UDP)-glucuronosyltransferase has been investigated . Of all the immobilization methods used (covalent binding, adsorption by ionic or hydrophobic interactions), only entrapment of microsomes into alginate beads in the presence of polyethyleneimine was effective in producing high glucuronidation rates, thus leading to the formation of large amounts of metabolites . The performance of the bioreactor was optimized with the drug 3'-azido-3'-deoxythymidine (AZT), active against the human immunodeficiency virus, as a model substrate of UDP-glucuronosyltransferase . Calcium (12 mM) could optimally improve the stability of microsomes entrapped in alginate beads . Upon immobilization, enzyme activation occurred, leading to a fivefold increase in specific activity . The determination of apparent Km and Vmax revealed that AZT was a better substrate for the immobilized enzyme than free microsomes . The AZT-glucuronide production obtained after 6 h was threefold higher than that observed with free microsomes . This bioreactor was also efficient in production of glucuronides from structurally different compounds such as bilirubin, 4-nitrophenol, clofibric acid, pirprofen, dextrorphan or morphine, the corresponding glucuronide of which possesses pharmacological or toxicological interest. J Biotechnol, 1991 Jul, 19(2-3), 241 - 57 Polyvinyl alcohol and polyethylene glycol as protectants against fluid-mechanical injury of freely-suspended animal cells (CRL 8018); Michaels JD et al.; Two identical bioreactors run in parallel were used to examine the phenomenological characteristics of two additives, polyethylene glycol (PEG) and polyvinyl alcohol (PVA), used as protectants against fluid-mechanical cell damage . Cell-protecting ability was evaluated by comparing apparent cell growth rates of freely suspended CRL-8018 hybridoma cells cultured in serum-free medium under surface aerated conditions whereby cell damage is due to bubble entrainment and breakup . PEG of various molecular weights was used to determine whether the size of the polymer has significant effects on PEG's cell-protecting capabilities . All the PEG's with molecular weights larger than 1400 showed similar protective effects . The effect of PEG concentration was then evaluated and results showed that concentrations greater than 0.05% w/v did not significantly improve the cell-protecting properties . Direct comparisons made between the PVA, PEG, and pluronic F68 as cell protectants showed that PEG protected cells better than F68 and that PVA provided even better protection than PEG . The mechanism of protection, fluid-mechanical or biological in nature, was examined by growing the cells in additive from the beginning of the experiment (long-term exposure), or adding the additive after the cells had been agitated at rates detrimental to the cells (short-term exposure) . In agreement with results reported previously on PEG and F68, fast-acting protection was seen . This implies a fluid-mechanical rather than a biological protection mechanism . In an attempt to correlate interfacial properties of the resulting media with shear protection, interfacial tension and viscosity measurements of all the media were made . On the basis of these measurements, we find no definitive correlations for evaluating these additives' cell-protecting capabilities. Appl Environ Microbiol, 1991 Jun, 57(6), 1602 - 8 Performance characterization of a model bioreactor for the biodegradation of trichloroethylene by Pseudomonas cepacia G4; Folsom BR et al.; Pseudomonas cepacia G4 grown in chemostats with phenol demonstrated constant specific degradation rates for both phenol and trichloroethylene (TCE) over a range of dilution rates . Washout of cells from chemostats was evident at a dilution rate of 0.2 h-1 at 28 degrees C . Increased phenol concentrations in the nutrient feed led to increased biomass production with constant specific degradation rates for both phenol and TCE . The addition of lactate to the phenol feed led to increased biomass production but lowered specific phenol and TCE degradation rates . The maximum potential for TCE degradation was about 1.1 g per day per g of cell protein . Cell growth and degradation kinetic parameters were used in the design of a recirculating bioreactor for TCE degradation . In this reactor, the total amount of TCE degraded increased as either reaction time or biomass was increased . TCE degradation was observed up to 300 microM TCE with no significant decreases in rates . On the average, this reactor was able to degrade 0.7 g of TCE per day per g of cell protein . These results demonstrate the feasibility of TCE bioremediation through the use of bioreactors. Curr Opin Biotechnol, 1991 Jun, 2(3), 408 - 12 Integrated product formation and recovery; Daugulis AJ; As continues to be demonstrated, the in situ recovery of selected products froma bioreactor can have a significant positive impact on production . The strategies that are focused on here are: aqueous two-phase biocatalysis; non-aqueous biocatalysis; and membrane-enhanced biocatalysis . Additional fundamental understanding of molecular partitioning and biocatalytic activity in these environments will facilitate the rational selection of the components involved in these processing strategies. Curr Opin Biotechnol, 1991 Jun, 2(3), 375 - 9 Large-scale mammalian cell culture: methods, applications and products; Spier RE; Animal cell cultures are used to generate products of enormous biotechnological value . These systems rely on conventional manufacturing techniques using organisms that are the result of either cell fusions or genetic engineering . A wealth of new techniques has allowed improvements and developments to be made in culture medium composition, cell modification, and bioreactor design and operation . This progress is expected to be commercially exploited as new products reach the market place. Curr Opin Biotechnol, 1991 Jun, 2(3), 365 - 9 Large-scale insect cell culture: methods, applications and products; Goosen MF; The primary development in large-scale insect cell culture over the past year has been the continuing accumulation of documented evidence (fundamental and applied) that conventional aerated stirred-tank and air-lift bioreactors may be employed for insect cell cultivation and recombinant protein production, provided that air sparging, agitation, and the addition to the medium of Pluronic F-68 and methyl cellulose polymers are carefully controlled. J Biotechnol, 1991 Jun, 19(1), 99 - 110 Solasodine production from self-immobilised Solanum aviculare cells; Tsoulpha P et al.; Procedures were developed for 'self-immobilisation' of Solanum aviculare cells to eliminate the need for artificial immobilisation supports . Depending on the cytokinin used in liquid medium, compact aggregates 0.4-2.0 cm in diameter were formed without dispersed cells also being present . Histochemical analysis showed that the aggregates were structurally organised to facilitate nutrient transport . Growth, sugar uptake and solasodine production were measured in shake-flask cultures . Most of the product was stored in the aggregates to reach a maximum concentration of 0.3% dry weight; this is between 1.5 and 10 times the levels reported for suspended cells under similar conditions . A substantial amount of solasodine was produced after growth ceased . The maximum rate of solasodine production was about 0.22 mg g-1 d-1 . A simple air-driven bioreactor was tested for culture of the aggregates; solasodine yields were comparable to those measured in shake flasks. Anal Biochem, 1991 Apr, 194(1), 16 - 24 Flow injection analysis of lactose using covalently immobilized beta-galactosidase, mutarotase, and glucose oxidase/peroxidase on a 2-fluoro-1-methylpyridinium salt-activated Fractogel support; Narinesingh D et al.; Milk samples were analyzed for their lactose content using flow injection analysis and incorporating immobilized beta-galactosidase or beta-galactosidase/mutarotase and glucose oxidase/peroxidase bioreactors . These enzymes were immobilized, under mild conditions, on to a 2-fluoro-1-methylpyridinium salt-activated Fractogel support . The use of a phosphate buffer (0.15 M) was found to facilitate the rapid mutarotation of alpha-D-glucose and hence could obviate the need for the more expensive mutarotase . The chromogenic agents of choice for monitoring the reaction were 3-methyl-2-benzothiazolinone hydrazone and 3-dimethylaminobenzoic acid . Linearity was observed over the concentration range 16-160 micrograms/ml using lactose standards (r = 0.996) . Between 30 and 40 milk samples/h can be analyzed . Comparisons are made with existing HPLC and alkaline methylamine methods for a range of milk matrices . The FIA method consistently gives the lowest standard deviations and coefficient of variation for the various milk matrices analyzed. Cell Biophys, 1991 Apr, 18(2), 99 - 121 Possible role of cell cycle-dependent morphology, geometry, and mechanical properties in tumor cell metastasis; Needham D; Studies that examine the shear- and abrasion-sensitivity of proliferating cells are important in order to understand the behavior of hybridoma cells in bioreactor culture and metastasizing cancer cells in the bloodstream . Little is known about the link between morphology, structure, and mechanical properties of a given cell line, especially with respect to variations throughout the cell cycle . In our experiments with GAP A3 hybridoma cells, distinct cell morphologies were identified and correlated with phases of the cell cycle by video microscopic observation of synchronized cells, and of individual cells that were followed throughout their cell cycle . Micropipet manipulation was used to measure the geometrical (cell volume) and mechanical (apparent cell viscosity) properties of single cells . As the cell cycle progressed at 37 degrees C, an increase in cell volume from 1400 microns 3 to 5700 microns 3 was accompanied by an increase in apparent cell viscosity from 430 poise to 12,000 poise, consistent with an accumulation of more cytoplasmic material in the "older" cells . Hybridomas are representative of the various leukemias derived from hemopoietic cells, and even though as a whole, they appeared to be rather shear-insensitive, the wide range of property values demonstrates that a given cell line cannot be characterized by a single value for any one property, and that properties must be related to the cell cycle when considering proliferating cells . It is interesting to see if distinct stages in the metastatic sequence of events might correlate with any of these physical features of the cell cycle, irrespective of cell type or cell line . For example, the cytokinetic doublet could represent a fragile structure that may fail and produce cell death under fluid-shear conditions that would not affect the cells at any other stage in the cell cycle . Identifying such cell cycle-dependent features in metastasizing cancer cells could lead to a better understanding of the metastatic process and to possible clinical treatments directed at making cells more shear- and abrasion-sensitive, and therefore, more likely to be killed by the natural hydrodynamic forces of the circulatory system. Biotechnology (N Y), 1991 Apr, 9(4), 367 - 71 Bioconversion of n-octane to octanoic acid by a recombinant Escherichia coli cultured in a two-liquid phase bioreactor; Favre-Bulle O et al.; The alk genes from the catabolic OCT plasmid of Pseudomonas oleovorans, which encode the enzymes involved in the oxidation of n-alkanes to carboxylic acids, were introduced into E . coli W3110 . The resulting recombinant converts n-octane in a two-liquid phase medium into the corresponding alkanoate and excretes this compound into the aqueous phase . The rate of octanoic acid production by the recombinant E . coli is equal to or better than the alkane oxidation rate of P . oleovorans, suggesting that two-liquid phase fermentations with E . coli might have future industrial applications. Magn Reson Med, 1991 Mar, 18(1), 181 - 92 Iteration of hybridoma growth and productivity in hollow fiber bioreactors using 31P NMR; Gillies RJ et al.; Applications of nuclear magnetic resonance (NMR) spectroscopy to isolated or cultured mammalian cells have been limited because of technical difficulties in maintaining cultures at the extremely high densities required by NMR . Among the well-engineered systems available for such analyses, hollow fiber bioreactors (HFBRs) can maintain the greatest cell density . This attribute of HFBRs makes them ideal for application to NMR-based studies . These systems are currently being applied in biotechnology, where they are used for the production of mammalian cell-derived products, such as monoclonal antibodies . In this paper, the application of a HFBR system designed especially for NMR-based investigations is described . Performance of this system is monitored by NMR and the resulting stability and density of hybridoma cultures are reported . The resulting signal-to-noise per unit time is the highest seen to date for a mammalian cell system. Z Naturforsch {C}, 1991 Mar-Apr, 46(3-4), 204 - 9 Marine biosurfactants, II . Production and characterization of an anionic trehalose tetraester from the marine bacterium Arthrobacter sp . EK 1; Passeri A et al.; Within a screening for biosurfactants we could isolate various n-alkanes utilizing marine bacteria which were capable of synthesizing glycolipids . One strain was identified as Arthrobacter sp . EK 1 which produced trehalose lipids . After purification by column and thick layer chromatography the main fraction, an anionic 2,3,4,2'-trehalose tetraester, was obtained . The chain lengths of fatty acids ranged from 8 up to 14, furthermore succinate could be detected . Since the place of substitution of succinate has so far not been cited in literature, a definitive structural elucidation was carried out chemically by hydroboration and by 1H, 2D1H, 13C and 13C-1H correlation NMR measurements . All investigations confirmed the exact position of succinate at C 2 atom of trehalose . After improvement of growth conditions the production of the trehalose tetraester increased up to 4.8 milligrams during a fermentation in 20 l bioreactor under nitrogen limitation. Biotechnol Prog, 1991 Mar-Apr, 7(2), 130 - 9 Transport and kinetics in sandwiched membrane bioreactors; Jeong YS et al.; A bioreactor in which living yeast cells are sandwiched between an ultrafiltration membrane and a reverse osmosis membrane was constructed, and experiments were performed for the conversion of substrate glucose to product ethanol . A set of equations that include both transport through a series of barrier layers and bioreaction rate were developed to predict the performance of the sandwich bioreactor . The above equations were solved by using numerical values for the transport parameter and the bioreaction rate constant, and the results are compared with the experimental data. Appl Microbiol Biotechnol, 1991 Mar, 34(6), 726 - 9 A hybrid bioreactor for high density cultivation of plant cell suspensions; Kim DI et al.; A hybrid bioreactor was developed for the production of secondary metabolites from high density cultivation of plant cell suspensions . Some of the advantages of both air-lift and cell-lift by agitation were combined . The addition of a decanting column also made it possible to run a perfusion system for high density culture or to run a two-stage culture efficiently . Cell growth and the production of berberine from Thalictrum rugosum in the hybrid bioreactor are reported in this paper . A cell density up to 31 g/l was obtained by perfusion without any problems in mixing or loss of cell viability and the specific berberine productivity was comparable to that in shake flasks . The maximum berberine concentration was 88 mg/l at 3 weeks of operation and declined thereafter. Biotechnol Prog, 1991 Mar-Apr, 7(2), 85 - 92 Propagation of recombinant vaccinia virus in HeLa cells: adsorption kinetics and replication in batch cultures; Chillakuru RA et al.; The influence of various culture parameters on infection and replication of recombinant vaccinia virus in HeLa cells was examined during various phases of viral replication . A modified form of the model of Valentine and Allison (Biochim . Biophys . Acta 1960, 40, 393-399) model was used to predict successfully the viral adsorption rates in cell suspensions . An experimentally determined aggregation factor, epsilon, was included in the model to account for deviations of the observed adsorption rates from those predicted by the earlier model . It was also shown that the ionic strength, ionic species, and serum proteins present in the medium significantly altered the adsorption kinetics of the virus . The lysosomotropic base chloroquine was found to enhance viral infection more than 2-fold during the penetration step of viral infection . It was also demonstrated that cells infected during the exponential growth phase gave higher viral yields than those infected during the lag or stationary growth phases and the initial viral MOI did not significantly alter viral yields . Finally, it was demonstrated that viral infection of HeLa cells grown in 4-L bioreactor batch cultures resulted in increased death and glucose uptake rates and significantly lower growth rates. Cytotechnology, 1991 Feb, 5(2), 129 - 39 Long term and large-scale cultivation of human hepatoma Hep G2 cells in hollow fiber bioreactor . Cultivation of human hepatoma Hep G2 in hollow fiber bioreactor; Liu JJ et al.; Long-term and large scale cultivation of an anchorage-dependent cell line using an industrial scale hollow fiber perfusion bioreactor is described . Hep G2 cells (a human hepatoma cell line) were cultivated in an Acusyst-P (Endotronic) with a total fiber surface area of 7.2 m2 6 x 1.2m2) to produce Hep G2 crude conditioned medium (CCM) . Pretreatment of the cellulose acetate hollow fibers with collagen enhances the attachment of the anchorage-dependent cells . We have succeeded in growing the Hep G2 cells in an antibiotics- and serum-free IMDM medium, supplemented with 50 micrograms/ml of Hep G2 CCM protein at inoculation . The Hep G2 cells replicate and secrete CCM protein in quantities comparable to those produced in DMEM containing 10% fetal calf serum (FCS) . The highest CCM protein productivity during the 80-day cultivation was 1.1 g/day with a total of 30 g of protein accumulated . Hep G2 CCM (20-40 micrograms protein/ml) was comparable to or even better than 10% FCS in supporting the growth of Molt-4 (a human T leukemia cell line) and FO (a mouse myeloma cell line) cells in vitro . The availability of this large amount of Hep G2 CCM will aid the further purification and characterization of growth factor(s) which could be used as serum substituents. J Biotechnol, 1991 Feb, 17(2), 133 - 46 Pilot scale production of a Trichoderma reesei endo-beta-glucanase by brewer's yeast; Zurbriggen BD et al.; Endo-beta-glucanase I (EGI) of Trichoderma reesei was produced in laboratory and pilot scale using recombinant strains of "bottom-fermenting" Saccharomyces cerevisiae . The gene eg/1 was integrated in the chromosome or an expression cassette was inserted on a multicopy plasmid . Expression levels were compared in a laboratory scale bioreactor . The best EGI-producing strain was cultivated in pilot scale . Adsorbent treatment was used to remove endogenous yeast proteins and other impurities from the culture filtrate during concentration . Effective pilot scale one-step purification of the EGI protein was obtained using DEAE-Sepharose, on which EGI was weakly bound . The purified enzyme reacted with antibodies prepared against T . reesei EGI and catalyzed the hydrolysis of both insoluble and soluble substrates. J Immunol, 1991 Jan 1, 146(1), 250 - 6 Recombinant soluble human complement receptor type 1 inhibits inflammation in the reversed passive arthus reaction in rats; Yeh CG et al.; The human CR1 was genetically engineered by site directed mutagenesis into a truncated form which was secreted from transfected Chinese hamster ovary cells . This soluble recombinant CR1 (sCR1) was purified from the supernatants of the Chinese hamster ovary cells cultured in a hollow fiber bioreactor . sCR1 inhibits the C3 and C5 convertases of the classical and the alternative pathways in vitro . The ability of sCR1 to inhibit the immune complex-mediated inflammation in vivo was tested in a rat reversed passive Arthus reaction model . Administration of sCR1 at the dermal sites reduced the Arthus vasculitis in a dose-dependent manner as judged by both gross and microscopic examination, as well as by immunohistologic localization of C3 and C5b-9 neoantigen deposits . These data suggest that sCR1 inhibits the Arthus reaction by interrupting the activation of the C cascade, hence limiting the detrimental immune complex-induced tissue damage in vivo. Biotechnology, 1991, 17, 305 - 26 Optimization of the microenvironment for mammalian cell culture in flexible collagen microspheres in a fluidized-bed bioreactor; Vournakis JN et al.; Flexible, three-dimensional, collagen Microspheres have been developed to actively promote a natural, optimal microenvironment for large-scale tissue culture of mammalian cells . The transport of nutrients into and cell products out of the Microspheres is enhanced by forced convective flow, which is the result of the tumbling of Microspheres and the dynamic properties of media flow in the fluidized-bed bioreactor . The collagen Microspheres have important characteristics of composition and morphology essential for optimal cell-matrix and cell-cell interactions . These interactions lead to high cell density and productivity through the dynamic modification of the microenvironment by cell-derived extracellular constituents . The collagen and Microsphere/fluidized-bed system provides the means to control and optimize the diffusive and contact components of the cells' microenvironment . Adaptation of cells to this microenvironment often results in dramatic increases in cell-specific productivity . Production of biotherapeutics in this process can be routinely performed in serum-free media, often leading to high productivity and product quality. Biotechnology, 1991, 17, 107 - 18 Nuclear magnetic resonance spectroscopy of dense cell populations for metabolic studies and bioreactor engineering: a synergistic partnership; Dale BE et al.; Commercial exploitation of the fruits of recombinant DNA and cell fusion technologies is significantly limited by the lack of fundamental metabolic information on the cell lines of interest, whether these are plant, animal, insect, or microbial cells . NMR can help to provide this information and thereby improve bioreactor design and operation . However, in the case of on-line NMR of dense cell culture devices for metabolic studies, these devices are inherently heterogeneous bioreactors . To ensure that the metabolic information generated is reliable, a number of precautions should be taken . These are the same precautions that should be taken to ensure that commercial bioreactors operate in a reaction-controlled regime . Therefore, reactor engineering methodologies, particularly diffusion and reaction analyses and reaction monitoring by whole-cell NMR must go hand in hand, each extending, complementing, and validating the other. Appl Biochem Biotechnol, 1991 Spring, 28-29, 457 - 69 Performance of trickle-bed bioreactors for converting synthesis gas to methane; Kimmel DE et al.; Carbon monoxide, H2, and CO2 in synthesis gas can be converted to CH4 by employing a triculture of Rhodospirillum rubrum, Methanosarcina barkeri, and Methanobacterium formicicum . Trickle-bed reactors have been found to be effective for this conversion because of their high mass-transfer coefficients . This paper compares results obtained for the conversion of synthesis gas to CH4 in 5-cm- and 16.5-cm-diameter trickle-bed reactors . Mass-transfer and scale-up parameters are defined, and light requirements for R . rubrum are considered in bioreactor design. Folia Microbiol (Praha), 1991, 36(1), 75 - 80 Immobilization of Aspergillus clavatus in a membrane bioreactor; Belushkina IA et al.; The possibility of the immobilization of A . clavatus in a membrane bioreactor which contains the nuclear membrane is investigated . The immobilization of cells in this bioreactor permits to increase the time of the productive functioning of the cells and avoids the procedure of a biomass separation from the cultural liquid. Biotechnol Genet Eng Rev, 1991, 9, 327 - 67 Heterologous protein production by filamentous fungi; Jeenes DJ et al.; There are clearly many facets to successful production of heterologous proteins from filamentous fungi . The objectives are to exploit the natural ability of some species to secrete high levels of protein . The heterologous target proteins produced in a fungal host must be acceptable to the public and be economic to produce, i.e . the targets must be authentic (in structure and activity) and be produced in high yield to necessary levels of purity . The appearance of heterologous products from fungi on the market is testament to some success but, equally, there are considerable limitations in our ability to produce desired yields of many target proteins . We endorse the view of van den Hondel, Punt and van Gorcom (1991) that for the commercial production of heterologous proteins from filamentous fungi more information is required on transcriptional control, introns, mRNA stability and processing, translational efficiency, protein secretion, glycosylation and proteolysis . In addition, there is scope for yield improvement based on a better understanding of the physiology of growth/product secretion coupled to appropriate bioreactor operation . The authenticity of product is an aspect which will assume increasing importance, particularly for therapeutic proteins . The level at which the structures and functional activity of heterologous proteins are assessed will ultimately be determined by legislation . The analytical methods currently available are not always sufficient, for example, to reveal folded structures, and most proteins are not amenable to analysis by two-dimensional NMR . The authenticity of target heterologous proteins will also need to be assessed in relation to the glycosylation level and pattern . This is not easily done and explains the paucity of detailed information published to date on glycosylation of fungal proteins . Novel engineered proteins are already being produced from filamentous fungi where expression is an aid to investigation of structure-function relationships . Commercial production of such engineered proteins will require approval subject to a range of stringently applied tests and analyses . This imposes an even greater need to be able to specify and control, in a rational manner, the structures of recombinant proteins . The research needs for realization of improved yields are equally important in assuring authenticity of product . It is encouraging that progress is being made on all fronts, primarily with Aspergillus spp . and T . reesei, but also with other species, such as N . crassa. Adv Biochem Eng Biotechnol, 1991, 44, 65 - 95 Shear effects on suspended cells; Merchuk JC; Shear has been mainly considered in the technical literature as a destructive element, when applied to microorganisms and cells . Indeed, most of the research work addressing the subject aims at the identification of damaging levels of shear on a given culture . The present work is focused on the effects of shear on suspended cultures before the damaging levels are attained . Inspection of the literature reveals that shear may influence growth rate, cellular volume, metabolite production rate and distribution, and membrane permeabilities . Available devices for study and evaluation of shear effects on suspended cultures are described and critically reviewed . The review reveals the possibility of an influence of the liquid dynamics on the kinetics of the biochemical process . This is relevant for bioreactor design and scale up, and stresses the importance of using structural bioreactor models in order to describe the hydrodynamics of the system. Adv Biochem Eng Biotechnol, 1991, 44, 27 - 64 Membrane bioreactors: present and prospects; Chang HN et al.; Membrane bioreactors have a very handy in-situ separation capability lacking in other types of bioreactors . Combining various functions of membrane separations and biocatalyst characteristics of enzymes, microbial cells, organelles, animal and plant tissues can generate quite a number of membrane bioreactor systems . The cell retaining property of membranes and selective removal of inhibitory byproducts makes high cell density culture possible and utilizes enzyme catalytic activity better, which leads to high productivity of bioreactors . Enzyme reactions utilizing cofactors and hydrolysis of macromolecules are advantageous in membrane bioreactors . Anaerobic cell culture may be efficiently carried out in membrane cell recycle systems, while aerobic cultures work well in dual hollow fiber reactors . Animal and plant cells have much a better chance of success in membrane reactors because of the protective environment of the reactor and the small oxygen uptake rate of these cells . Industrial use of these reactors are still in its infancy and limited to enzyme and animal tissue culture, but applications will expand as existing problems are resolved. J Chem Technol Biotechnol, 1991, 51(3), 323 - 34 Heat transfer in bubble column and airlift bioreactors: Newtonian and non-Newtonian fermentation broths; Kawase Y et al.; A theoretical model has been developed for heat transfer in bubble column and airlift bioreactors, which is applicable for Newtonian and non-Newtonian fermentation media . The proposed model is based on a similarity between heat transfer in gas-sparged pneumatic reactors and turbulent natural convection . The applicability of the proposed model was discussed using a wide range of experimental data, and good agreement was obtained. J Chem Technol Biotechnol, 1991, 52(4), 499 - 509 Design considerations for an immobilized cell bioreactor operating in a batch recirculation mode; Lakhwala F et al.; Immobilizing microbial cells and enzymes used in biological and biochemical processes is advantageous and has been a subject of intensive study in recent years . Successful implementation of this technology requires complete understanding of physical, chemical and biological parameters which influence the performance of such a system . This paper focuses on a few basic design considerations which are essential to the design and operation of immobilized cell bioreactors . A process using microorganisms entrapped in calcium alginate gel as a biocatalyst is considered . This system is used to biodegrade the organic compound, phenol . A batch reactor operated in a recirculation mode is used, and parameters like concentration of dissolved oxygen, concentration of the organic compound, bead size, biomass loading and the flow rate are studied . The bioreactor can be operated within many operating windows where one of the above parameters may be rate limiting . With the help of conceptual and experimental data, the influence of the above parameters on the reaction rates is discussed. J Chem Technol Biotechnol, 1991, 50(2), 167 - 80 A high containment polymodal pilot-plant fermenter--design concepts; Hambleton P et al.; A 225 dm3 pilot-plant bioreactor system has been designed and constructed that is suitable for biohazardous fermentations . The design enables operation at containment levels above the requirements of good industrial large-scale practice (GILSP) without secondary containment of the whole plant . The main biosafety features of the systems include the use of steam barriers on O-ring seals, supply lines and stirrer seals, multiple O-ring seals, piping of condensate lines and pressure relief systems to a 'kill tank', double filtration of inlet and off gases and a mobile isolation unit that allows localised containment of sample valve and probe entry ports . The fermenter can, with minor modifications, be operated as a bottom-or top-stirred reactor for the culture of microbial or animal cells, or as an airlift reactor . The design offers considerable flexibility that could prove cost-effective for process development and production . The relevance of the various design features to enable bioreactor operations at pilot-plant scale to be carried out in compliance with current guidelines for large-scale culture of recombinant microorganisms and microbial pathogens is discussed. Bioprocess Technol, 1991, 13, 112 - 43 Bioreactor and process design for large-scale mammalian cell culture manufacturing; Nelson KL et al.; Good Manufacturing Practice for pharmaceuticals requires that the manufacturing processes be controlled and reproducible . The biological nature of cell culture-based processes lends them an inherently higher variability than is generally found for processes involving production of defined chemical entities . As one regulatory body has pointed out, this places a greater emphasis on in-process controls and adherence to GMPs in the manufacture of cell culture products . Design of bioreactors and associated process control systems is a key element in the successful implementation of a commercial-scale cell culture manufacturing process capable of meeting such high standards . It should be noted that reactor and control system designs for animal cell culture are still very much in a state of evolution from the modified bacterial fermentation systems that currently predominate, and it is difficult to predict how design strategies may change in the coming years . Having said this, however, it should be clear from the information presented here that satisfactory processes can be devised today using proven equipment configurations such as the stirred-tank reactor. Cytotechnology, 1991 Jan, 5(1), 69 - 82 Serum-free medium for fermentor cultures of hybridomas; Merten OW et al.; Hybridomas lend themselves particularly well to large scale cultivation techniques since they grow as single cells in suspension without requiring attachment to a substrate . Furthermore, many cell strains have been adapted to grow in serum-free (SF) media to a similar cell density and antibody production as in serum containing media . This review will concern itself mainly with the cultivation of hybridomas in SF-media in bioreactors of various types with the ultimate goal of producing large quantities of monoclonal antibodies (mAb). FEMS Microbiol Rev, 1990 Dec, 7(3-4), 273 - 8 Biodegradation of low-molecular-weight halogenated hydrocarbons by methanotrophic bacteria; Hanson RS et al.; Low-molecular-weight halogenated hydrocarbons are susceptible to degradation by anaerobic and aerobic bacteria . The methanotrophic bacterium Methylosinus trichosporium 0B3b degrades trichloroethylene more rapidly than other bacteria examined to date . Expression of soluble methane monooxygenase (MMO) is correlated with high rates of biodegradation . An analysis of 16 S rRNA sequences of 11 ribosomal RNAs from type I, type II and type X methanotrophs and methanol-utilizing bacteria have revealed four clusters of phylogenetically related methylotrophs . This information may be useful for the identification and enumeration of methylotrophs in bioreactors and other environments during remediation of contaminated waters. Eur J Epidemiol, 1990 Dec, 6(4), 386 - 97 Establishment of stable mouse/human-human hybrid cell lines producing large amounts of anti-tetanus human monoclonal antibodies with high neutralizing activity; Kamei M et al.; To establish stable hybrid cell lines producing human anti-tetanus antibody with high toxin-neutralizing activity, peripheral lymphocytes from humans hyperimmunized with tetanus toxoid were, after in vitro antigen stimulation, fused with a mouse/human heteromyeloma or human lymphoblastoid cell line and cloned . Unlike the IgM secretors (six clones), the IgG secretors we obtained (six clones) produced anti-tetanus human monoclonal antibodies with high neutralizing activity (the highest one, cell line G2, 4.3 IU/100 micrograms IgG) . Appropriate combinations of three or four kinds of monoclonal antibodies of the IgG type resulted in markedly increased neutralizing activity comparable with that of anti-tetanus human polyclonal immunoglobulin preparations currently used clinically on the basis of toxin-specific IgG content . Five of these cell lines produced 10-20 micrograms of antibody per ml for more than 3 months . The cell line G2 produced 6 mg of antibody per day in serum-free medium in a 500-ml bioreactor in perfusion culture and 13-104 mg in a nude mouse . These cell lines satisfied, for the first time, the minimal requirements for applying human monoclonal antibodies to clinical use. Appl Microbiol Biotechnol, 1990 Dec, 34(3), 350 - 3 Ambruticin S production in air-lift and stirred-tank bioreactors; Hopf NW et al.; Using the method of equi-inocular synchronized comparative fermentation (EISCF) the cultivation of Sorangium cellulosum So ce 10 and production of the polyketide antibiotic ambruticin S was compared in stirred-tank and air-lift reactors of different geometry . This method requires that inocula originate from the same pre-culture and cultivation parameters are synchronized to similar values . Similar ambruticin yields were obtained from both reactor systems provided that the concentration of dissolved oxygen (DO) was maintained above a certain value (ca . 40%) . For cultivation of S . cellulosum it is the DO level rather than the oxygen transfer rate which presents the proper criterion for scale-up and comparative reactor studies. Biotechnology (N Y), 1990 Dec, 8(12), 1282 - 5 A nuclear magnetic resonance technique for determining hybridoma cell concentration in hollow fiber bioreactors; Mancuso A et al.; We have developed a technique for determining cell concentration in a hollow fiber bioreactor based on 23Na nuclear magnetic resonance (NMR) spectroscopy . Cell concentrations determined with this method agreed closely with concentrations calculated from 31P NMR nucleoside triphosphate (NTP) measurements and oxygen consumption rate measurements . Oxygen transfer limitations, which can complicate cell mass determinations based on oxygen consumption rates, were shown to be negligible for the bioreactor used . Specific antibody production rates in hollow fiber culture, calculated from these cell number estimates, were similar to those found in suspension culture for this cell line. Anal Chem, 1990 Nov 15, 62(22), 2418 - 24 Use of ionomer membranes to enhance the selectivity of electrode-based biosensors in flow-injection analysis; Rosario SA et al.; The use of ionomer membranes to enhance the selectivity of potentiometric enzyme electrodes in flow-injection measurement arrangements is examined . The ionomer membranes employed are permeable to analyte substrates but relatively impermeable to detectable ions that would normally interfere with the measurement of the substrates if the enzyme electrodes were in direct contact with the sample . As a model system, the selectivity of enzyme electrodes prepared with nonactin-based ammonium-sensitive polymeric membranes is evaluated . In the preferred configuration, a thin hydrophilic anion-exchange membrane is incorporated within a flow-through dialysis unit upstream from the enzyme-electrode detector . As the sample passes through the dialysis unit, neutral or anionic analyte molecules (urea or glutamine) move through the membrane while the permeation of endogenous ammonium ions and other cations in the sample is retarded . A flowing recipient buffer on the other side of the membrane carries the analyte substrate to the enzyme-electrode detector . Enhancements in selectivity for analyte substrates over endogenous ammonium and potassium ions are greater than or equal to 9-fold when compared to enzyme-electrode flow-injection analysis (FIA) systems assembled without the ionomer membrane unit . The analytical utility of the proposed system is demonstrated by the accurate measurements of urea in blood serum and L-glutamine in hybridoma bioreactor media. Appl Environ Microbiol, 1990 Nov, 56(11), 3255 - 60 Chlorophenol degradation coupled to sulfate reduction; Haggblom MM et al.; We studied chlorophenol degradation under sulfate-reducing conditions with an estuarine sediment inoculum . These cultures degraded 0.1 mM 2-, 3-, and 4-chlorophenol and 2,4-dichlorophenol within 120 to 220 days, but after refeeding with chlorophenols degradation took place in 40 days or less . Further refeeding greatly enhanced the rate of degradation . Sulfate consumption by the cultures corresponded to the stoichiometric values expected for complete oxidation of the chlorophenol to CO2 . Formation of sulfide from sulfate was confirmed with a radiotracer technique . No methane was formed, verifying that sulfate reduction was the electron sink . Addition of molybdate, a specific inhibitor of sulfate reduction, inhibited chlorophenol degradation completely . These results indicate that the chlorophenols were mineralized under sulfidogenic conditions and that substrate oxidation was coupled to sulfate reduction . In acclimated cultures the three monochlorophenol isomers and 2,4-dichlorophenol were degraded at rates of 8 to 37 mumol liter-1 day-1 . The relative rates of degradation were 4-chlorophenol greater than 3-chlorophenol greater than 2-chlorophenol, 2,4-dichlorophenol . Sulfidogenic cultures initiated with biomass from an anaerobic bioreactor used in treatment of pulp-bleaching effluents dechlorinated 2,4-dichlorophenol to 4-chlorophenol, which persisted, whereas 2,6-dichlorophenol was sequentially dechlorinated first to 2-chlorophenol and then to phenol. Cytotechnology, 1990 Nov, 4(3), 271 - 8 Multistage production of Autographa californica nuclear polyhedrosis virus in insect cell cultures; Kloppinger M et al.; The aim of our study was to establish an efficient system for the in vitro production of the insect pathogenic Autographa californica nuclear polyhedrosis virus in a Spodoptera frugiperda cell line . We optimized cultivation conditions for cell proliferation as well as for virus replication in a 1.5 litre stirred tank bioreactor . Cell and virus propagation were found to be optimal at a constant oxygen tension of 40% . In order to provide sufficient nutrients during virus synthesis filtration and perfusion devices were connected to the bioreactor . A virus production procedure in a repeated batch mode by using a two stage bioreactor system is described . Stage I was optimized for cell production and stage II for virus production. J Biotechnol, 1990 Nov, 16(3-4), 245 - 58 Growth kinetics of Chinese hamster ovary cells in a compact loop bioreactor . 3 . Selection and characterization of an anchorage-independent subline and medium improvement; Kurano N et al.; Four sublines of Chinese hamster ovary (CHO) cells were selected or cloned on a 10% fetal calf serum supplemented MEM-alpha medium . Three of them were monolayer cultures and could proliferate by 2000 times a week (mu = 1.1 d 1) in T-flasks . The other subline, S1, could grow in suspension even in static T-flask cultures . The stability in chromosome number of these cell lines was investigated . By evaluating the kinetic growth parameters, i.e . the specific rates of growth, glucose consumption and lactic acid production, and the yields of cells and lactic acid from glucose, the S1 cells were considered to be the most suitable subline for the bioreactor suspension culture . The S1 cells reached the greatest maximum of cell concentration among all cell lines tested because of their efficient glucose utilization . Observed nutrient limitations in the S1 cell culture was overcome by modification of the medium composition, that is addition of 10 mg l-1 hypoxanthine, 1 mg l-1 FeSO4.7H2O, and 0.1 mg l-1 sodium putrescine, elimination of glutamine, supplementation of 6 mM asparagine and double amount of isoleucine, leucine, methionine and vitamins other than ascorbic acid, cyanocobalamin and biotin, increase of NaHCO3 concentration from 26 to 40 mM, and finally decrease of NaCl concentration from 122 to 100 mM . With this modified medium, 7.2 X 10(6) ml-1 of the maximum cell concentration was observed in a glucose fed-batch culture, the cell concentration which was twice as much as in batch cultures with the original medium. Enzyme Microb Technol, 1990 Nov, 12(11), 824 - 9 Coiled tube membrane bioreactor for cultivation of hybridoma cells producing monoclonal antibodies; Hagedorn J et al.; A coiled tube membrane reactor was developed for the cultivation of mouse-mouse hybridoma cells producing monoclonal antibodies . The cell and antibody concentrations obtained in the membrane reactor were higher than that obtained in a batch spinner flask without a membrane . A mathematical model has been developed to describe the membrane transport coupled growth and product formation, and the physical and kinetic constants of the system were determined. Biotechnol Prog, 1990 Nov-Dec, 6(6), 458 - 64 Inclined sedimentation for selective retention of viable hybridomas in a continuous suspension bioreactor; Batt BC et al.; The continuous separation of nonviable hybridoma cells from viable hybridoma cells by using a narrow rectangular channel that is inclined from the vertical has been investigated experimentally . The effectiveness of the settler in selectively retaining viable hybridomas in the bioreactor while permitting the removal of nonviable hybridomas has been shown to depend on the flow rate through the settler . Intermediate flow rates through the settler have been found to provide the highest removal of nonviable hybridomas relative to viable hybridoma retention . At high dilution rates through the chemostat, over 95% of the viable cells could be partitioned to the bottom of the settler while over 50% of the nonviable cells are removed through the top of the settler . This successful separation is due to the significantly larger size of the viable hybridomas than the nonviable ones . A continuous perfusion experiment was performed in which an external inclined settler was used to retain virtually all of the viable hybridomas in the culture, while selectively removing from the culture approximately 20% of the nonviable cells that entered the settler . A stable viable cell concentration of 1.0 x 10(7) cells/mL was achieved, as was an antibody productivity of over 50 micrograms/(mL.day) . These represent 3- and 6-fold increases, respectively, over the values obtained from a chemostat culture without cell retention. Biotechnol Prog, 1990 Nov-Dec, 6(6), 452 - 7 Plant cell culture using a novel bioreactor: the magnetically stabilized fluidized bed; Bramble JL et al.; A novel bioreactor using magnetically stabilized fluidized bed (MSFB) technology has been developed that has certain advantages for cultivating cells continuously . In this system, the cells are protected from shear and are constrained to move through the fermenter in lock-step fashion by being immobilized in calcium alginate beads . The MSFB permits good mass transfer, minimizes particle collisions, and allows for the production of cells while maintaining a controlled cell residence time . Details of the experimental system are described . In addition, the experimental performance of an MSFB used to grow plant cells in batch mode is compared to the results obtained in shake flask culture. Biotechnol Prog, 1990 Nov-Dec, 6(6), 437 - 46 Effects of dissolved oxygen on hybridoma cell growth, metabolism, and antibody production kinetics in continuous culture; Ozturk SS et al.; The effects of dissolved oxygen concentration (DO) on hybridoma cell physiology were examined in a continuous stirred tank bioreactor with a murine hybridoma cell line (167.4G5.3) . Dissolved oxygen concentration was varied between 0% and 100% air saturation . Cell growth and viability, carbohydrate, amino acid, and energy metabolism, oxygen uptake, and antibody production rates were investigated . Cell growth was inhibited at both high and low DO . Cells could grow at 0% DO and maintain viability under a nitrogen atmosphere . Cell viability was higher at low DO . Glucose, glutamine, and oxygen consumption rates changed little at DO above 1% air saturation . However, the metabolic uptake rates changed below 1% DO, where growth became oxygen limited, and a Km value of 0.6% DO was obtained for the specific oxygen uptake rate . The metabolic rates of glucose, glutamine, lactate, and ammonia increased 2-3-fold as the DO dropped from 1% to 0% . Amino acid metabolism followed the same general pattern as that of glutamine and glucose . Alanine was the only amino acid produced . The consumption rates of amino acids changed little above 1% DO, but under anaerobic conditions the consumption rates of all amino acids increased severalfold . Cells obtained most of their metabolic energy from glutamine oxidation except under oxygen limitation, when glucose provided most of the energy . The calculated ATP production rate was only slightly influenced by DO and rose at 0% DO . Antibody concentration was highest at 35% DO, while the specific antibody production rate was insensitive to DO. Naturwissenschaften, 1990 Oct, 77(10), 465 - 71 {Industrial production of monoclonal antibodies}; Baron D; Murine monoclonal antibodies (mabs) are produced in either mouse ascites or bioreactors (spinner culture, stirred-tank reactor, airlift reactor, hollow-fiber reactor) . Human mabs are produced solely in bioreactors . Encapsulation represents a special technology . Hybridoma cells have to be adapted prior to growth in bioreactors . Of crucial importance is the construction of over-producing cell lines by cell- and gene-technological methods . Manipulated cell lines often produce modified mabs. Artif Organs, 1990 Oct, 14(5), 328 - 33 Gas supply across membranes in bioreactors for hepatocyte culture; Gerlach J et al.; The conditions required for hepatocyte cultures is a main topic in the development of bioreactors for hybrid liver support systems . The detoxification of ammonia and the synthesis of urea due to primary isolated hepatocytes was measured in order to compare two different models of gas supply in bioreactors: (a) indirect medium oxygenation and (b) direct membrane-contact oxygenation of the hepatocytes using polypropylene membranes . Increasing oxygen pressure promoted cell function . At day 6 of culture, urea synthesis was 0.8 +/- 0.3 mM in 21% of O2 cultures and 1.5 +/- 0.1 mM in oxygenated cultures . Alkalosis due to CO2 loss decreased ammonia metabolism . The direct membrane-contact oxygenation resulted in enhanced cell metabolism in comparison to medium oxygenation: urea synthesis at day six was 1.42 +/- 0.2 mM in 21% O2 cultures . Polypropylene oxygenation membranes proved to be sufficient for hepatocyte adhesion . Two functions can be integrated in one element in liver support systems using the investigated polypropylene membrane and the direct membrane-contact oxygenation: oxygenation with physiological oxygen pressure in bioreactors due to gas supply across the membrane and adhesion of hepatocytes in bioreactors on the membrane. Appl Microbiol Biotechnol, 1990 Oct, 34(1), 1 - 4 Effects of oxygen supply on the production of nikkomycin with immobilized cells of Streptomyces tendae; Truck HU et al.; For continuous production of the antibiotic nikkomycin immobilized cells have been used in a fluidized bed bioreactor . Cells of Streptomyces tendae were immobilized on sintered glass particles . Different biomass concentrations on the particles correspond to different thicknesses of mycelial layers because growth occurs only on the outer surface of the particles . The antibiotic productivity decreased with increasing layer thickness . In fermentations with higher concentrations of both biomass on the particles and dissolved oxygen levels of about 70% the productivity was also limited because of limited oxygen diffusion in the layers. J Biotechnol, 1990 Oct, 16(1-2), 123 - 35 Two-stage cultivation of Digitalis lanata cells: semicontinuous production of deacetyllanatoside C in 20-litre airlift bioreactors; Kreis W et al.; A two-stage cultivation method was employed to develop a semicontinuous biotransformation process for the production of deacetyllanatoside C, a cardenolide of the important digoxin series . Digitoxin was used as the substrate for biotransformation . The process was optimized in 1-l shake flasks and then established on the 20-l scale using two airlift bioreactors, one for cell growth (working volume 12 litres) and another for deacetyllanatoside C production (working volume 18 litres) . Growth and production phases were synchronized and the process finally ran semicontinuously in 7-d cycles . Six consecutive production runs were performed yielding a total of 43.8 g deacetyllanatoside C. Cytotechnology, 1990 Sep, 4(2), 145 - 53 The effect of bioreactor configuration on production of HIV and cell-virus interaction; Clarke JB et al.; In an attempt to establish a bioreactor system for generation of HIV that is practicable, efficient, biologically contained, and capable of scale up, the production of two strains of this virus was examined in suspension culture and the 'Porosphere' fixed bed system . HIV 1 and HIV 2 were grown successfully in both these types of reactor . The porosphere reactor theoretically appears to offer a better environment for HIV production, but evidence for significantly improved yields from this system, compared to suspension, was equivocal . However, this configuration facilitated media changes during culture . The data clearly showed that the culture system and cell environment significantly affected cell-virus interrelationships . Switches between lytic--and persistent--type infections, and changes in the virus population were observed. Cytotechnology, 1990 Sep, 4(2), 127 - 37 A two-compartment cell entrapment bioreactor with three different holding times for cells, high and low molecular weight compounds; Scholz M et al.; A new bioreactor for animal cell cultivation employs two compartments for cells and medium respectively . The two chambers are separated by an ultrafiltration membrane . Cells and solution of collagen or collagen/chitosan mixture were loaded to the cell chamber and were allowed to form gel inside . Contraction of the cell-laden gel occurred subsequently to create a new zone in the cell chamber . In such a bioreactor cells are retained in the reactor, the high molecular product(s) accumulate in the cell chamber, while the small molecular weight nutrients and metabolites are replenished and removed from the medium chamber . By adjusting the flow rates for cell and medium chambers, the resident time for cells, high and low molecular weight components of the system can be manipulated separately . The new bioreactor, in both flat-bed and hollow-fiber configurations, was used to cultivate recombinant human cell, 293, for Protein C production over 60 to 90 days. Biotechnol Prog, 1990 Sep-Oct, 6(5), 398 - 401 Practical considerations in the measurement of culture fluorescence; Coppella SJ et al.; We have examined practical considerations associated with the use of a commercially available fluorescence probe for in situ measurements in bioreactors . The optical path length of the measurement was first determined and a flow cell subsequently designed . The environment (agitation/aeration rates) of the probe was found to have a significant influence on the measurement . These effects were eliminated by placing the probe in a recycle loop using the flow cell . Fluorescence measurement in the recycle loop was verified to be representative of the cell sample and to not affect cell metabolism. Biotechnol Prog, 1990 Sep-Oct, 6(5), 391 - 7 Sparged animal cell bioreactors: mechanism of cell damage and Pluronic F-68 protection; Murhammer DW et al.; Pluronic F-68 is a widely used protective agent in sparged animal cell bioreactors . In this study, the attachment-independent Spodoptera frugiperda Sf9 insect cell line was used to explore the mechanism of this protective effect and the nature of cell damage in sparged bioreactors . First, bubble incorporation via cavitation or vortexing was induced by increasing the agitation rate in a surface-aerated bioreactor; insect cells were rapidly killed under these conditions of the absence of polyols . Supplementing the medium with 0.2% (w/v) Pluronic F-68, however, fully protected the cells . Next, cell growth was compared in two airlift bioreactors with similar geometry but different sparger design; one of these bioreactors consisted of a thin membrane distributor, while the other consisted of a porous stainless steel distributor . The flow rates and bubble sizes were comparable in the two bioreactors . Supplementing the medium with 0.2% (w/v) Pluronic F-68 provided full protection to cells growing in the bioreactor with the membrane distributor but provided essentially no protection in the bioreactor with the stainless steel distributor . These results strongly suggest that cell damage can occur in the vicinity of the gas distributor . In addition, these results demonstrate that bubble size and gas flow rate are not the only important considerations of cell damage in sparged bioreactors . A model of cell death in sparged bioreactors is presented. Biotechnol Prog, 1990 Sep-Oct, 6(5), 357 - 61 Immobilization of microbial cells in a mixed matrix of silicone polymer and calcium alginate gel: epoxidation of 1-octene by Nocardia corallina B-276 in organic media; Kawakami K et al.; Immobilization of Nocardia corallina B-276 was examined for production of 1,2-epoxyoctane from 1-octene in the presence of n-hexadecane as the organic solvent . Hydrophobic silicone polymer was the most suitable material for entrapment of the cells . Coentrapment of aqueous reaction medium into the silicone polymer matrix improved the epoxide productivity . It was also effective to immobilize the cells in a mixed matrix composed of silicone polymer and calcium alginate gel involving the reaction medium . In the organic monophase, the amount of epoxide accumulated with the cells immobilized in an almost equivolumetric composite of both materials was 2 and 7 times the amounts in the silicone and alginate single matrices, respectively, and it became larger than with the free cells in the aqueous-organic two-liquid phase after a longer period of batch operation . The use of such an optimized composite matrix enabled us to perform a relatively simple operation of the continuous three-phase bioreactor. Anal Biochem, 1990 Aug 1, 188(2), 325 - 9 Flow injection analysis of serum urea using urease covalently immobilized on 2-fluoro-1-methylpyridinium salt-activated fractogel and fluorescence detection; Narinesingh D et al.; Serum samples were analyzed for their urea content using fluorescence flow injection analysis incorporating an immobilized urease bioreactor and a gas permeable separator . The urease was immobilized under mild and facile conditions to a hydrophilic 2-fluoro-1-methylpyridinium-activated support . The ammonia released as a result of urease-catalyzed urea hydrolysis diffused through a gas permeable membrane into a constant stream of o-phthaldehyde solution to form a highly fluorescent product with lambda ex at 340 nm and lambda em at 455 nm . Up to 25 serum samples can be analyzed per hour . The within-day coefficient of variation (CV) was 1.12% and the day-to-day CV was 1.25% for serum containing 10.50 mg urea nitrogen dl-1 . The bioreactor shows excellent storage (at 4 degrees C) and operational stabilities (at 37 degrees C). Int J Artif Organs, 1990 Jul, 13(7), 436 - 41 Membranes as substrates for hepatocyte adhesion in liver support bioreactors; Gerlach J et al.; Fourteen membranes out of cellulose (CuprophanR), polyamide and polypropylene were compared in a cytocompatibility test using the cytokinetics and cytomorphology of primary hepatatocytes as parameters . Additionally, the impact of coating the membranes with collagen or fibronectin was investigated . Hepatocytes were not able to attach in acceptable amounts on investigated cellulose membranes . On polyamide and polypropylene membranes a sufficient cell seeding was possible . Coating with collagen or fibronectin improves the attachment and spreading on all membranes . Differences between collagen and fibronectin were detected, observing the morphology of the cells: on collagen, most of the cells spread, whilst on fibronectin, most of the cells spread and flattened polygonally . If the adhesion of hepatocytes prolongs their metabolic function, a large adhesion surface in bioreactors is necessary . To reach a high surface area for cell adhesion in bioreactors one possibility is the use of polyamide and polypropylene membranes. ASAIO Trans, 1990 Jul-Sep, 36(3), M727 - 9 A high density culture of hepatocytes using a reticulated polyvinyl formol resin; Yanagi K et al.; To enable high density culture of hepatocytes to be used as a hybrid artificial liver support or bioreactor system, collagen coated reticulated polyvinyl formal (PVF) resin (a filter material with a porosity of more than 80%) was used for the primary culture of hepatocytes . Stationary and perfusion culture experiments using PVF resin and monolayer culture were performed as control experiments . Due to the porous structure of the substrate material, hepatocytes were able to penetrate the reticulated pores of the PVF resin, and adhere to and spread on its surface . The densities of hepatocytes attained with PVF were about 10 times as high as those in the monolayer culture using conventional collagen coated Petri dishes . Hepatocytes immobilized in the PVF resin showed viability, as assessed by glutamic pyruvic transaminase (GPT) activity in the medium . Perfusion culture with PVF resin showed stable, high level metabolism, ammonium removal, and urea secretion comparable to the monolayer culture . It is concluded that perfusion culture with PVF resin is useful in attaining a high density culture of hepatocytes. Anal Biochem, 1990 Jul, 188(1), 72 - 81 Optimization of immobilized enzyme hydrolysis combined with high-performance liquid chromatography/thermospray mass spectrometry for the determination of neuropeptides; Voyksner RD et al.; Peptidases, including chymotrypsin, thermolysin, trypsin, V8 protease, and carboxypeptidases A, B, and Y, were immobilized for use in conjunction with HPLC/thermospray MS for the analysis of neuropeptides . The optimal operating conditions for each immobilized enzyme bioreactor were determined . Optimal hydrolysis usually occurred at the highest percentage of aqueous solution in the mobile phase at pH 7-8 and 40-50 degrees C . Often post-HPLC column addition of aqueous solutions before the bioreactor could improve activity and thermospray sensitivity without changing the HPLC separation . Enzymatic hydrolysis requirements were compatible under conditions for HPLC separation and thermospray MS detection of the selected neuropeptides . Synthetic alpha-, beta-, and gamma-endorphins were the primary neuropeptides used to evaluate on-line immobilized enzyme bioreactor/MS . HPLC followed by peptidase hydrolysis produced characteristic hydrolysis products for confirming the peptides' identity using thermospray MS detection . Furthermore, the peptide formed from enzymatic hydrolysis resulted in a MS ion current 10-40 times higher than that of the {M + 2H}2+ ion for unhydrolyzed beta-endorphin . The increased sensitivity achieved for detecting the hydrolysis products permits detection and quantitation of synthetic peptides down to 800 fmol. Biotechnol Prog, 1990 Jul-Aug, 6(4), 262 - 5 Enhancing oxygen transfer in surface-aerated bioreactors by stable foams; Ju LK et al.; To enhance oxygen transfer in surface-aeration bioreactors, stabilized foams were generated to increase the gas-liquid interfacial area by slowly introducing coarse bubbles into media containing fetal bovine serum . The bubble sparging rates were so low (i.e., 20 and 50 mL/h) that the contribution to oxygen transfer from these bubbles was due to foaming instead of bubbling . Furthermore, no physical cell damage caused by bubble sparging was observed . Oxygen transfer coefficients, kLa, in the bioreactors were measured in cell-free media . Without the foam-stabilizing agent (i.e., serum), no appreciable change in kLa was observed due to the bubble sparging . On the other hand, with serum, kLa increased with increasing serum content and bubble sparging rate and corresponded well with the degree of foaming . With 10% fetal bovine serum and a bubble sparging rate of 50 mL/h, kLa increased approximately 90% compared with no foaming . The enhancing effect of foam on oxygen transfer in surface aeration bioreactors has been further demonstrated with hybridoma cultures simultaneously grown in three identical bioreactors with and without stabilized foams. Appl Microbiol Biotechnol, 1990 Jul, 33(4), 407 - 9 Enhancement and stabilization of the production of glucoamylase by immobilized cells of Aureobasidium pullulans in a fluidized-bed reactor; Federici F et al.; Glucoamylase production by Aureobasidium pullulans A-124 was compared in free-living cells, cells immobilized in calcium alginate gel beads aerated on a rotary shaker (agitation rate 150 rpm), and immobilized cells aerated in an air bubble column reactor . Fermentation conditions in the bioreactor were established for bead concentration, substrate (starch) concentration, calcium chloride addition to the fermentation medium, and rate of aeration . Production of glucoamylase was optimized at approximately 1.5 units of enzyme activity/ml medium in the bioreactor under the following conditions: aeration rate, 2.0 vol air per working volume of the bioreactor (280 ml) per minute; gel bead concentration, 30% of the working volume; substrate (starch) concentration, at 0.3% (w/v); addition of calcium chloride to the medium at a final concentration of 0.01 M . Productivity levels were stabilized through the equivalent of ten batches of medium with the original inoculum of immobilized beads. J Biotechnol, 1990 Jul, 15(1-2), 57 - 69 The protective effect of serum against hydrodynamic damage of hybridoma cells in agitated and surface-aerated bioreactors; Kunas KT et al.; The effect of serum on the growth rate and metabolism of CRL-8018 hybridoma cells in an agitated, surface-aerated bioreactor was examined . In the employed well-controlled bioreactors at high agitation rates, hybridoma cells in medium containing 1% fetal bovine serum rapidly die in the presence of a vortex with accompanying gas-bubble entrainment, whereas non-agitated control cultures grow normally in medium containing 1% serum . Serum levels greater than 5% counteract the detrimental hydrodynamic effects due to agitation and bubble entrainment . The protective effect is present after short-term (less than 1 h) exposure to 10% serum concentration, suggesting a protection mechanism which is, at least in part, of a physical nature . The apparent cell yields on glucose, lactate, and glutamine decreased with decreasing growth rate due to low serum concentrations . The results are incorporated into a simple model in which the apparent growth rate is the sum of an invariable growth rate and a changing death rate. J Biotechnol, 1990 Jul, 15(1-2), 113 - 28 Growth behavior of Chinese hamster ovary cells in a compact loop bioreactor . 2 . Effects of medium components and waste products; Kurano N et al.; Effects of biochemical factors, i.e., medium components and metabolic byproducts, on growth of Chinese hamster ovary (CHO) cells were investigated . Glucose and ammonia were found to inhibit the growth . Kinetic analysis gave the inhibition constants, 0.14 g l-1 for ammonia and 5.0 g l-1 for glucose . Since glutamine was unstable and was a main source of ammonia, precise studies on glutamine degradation and ammonia formation process were done . By evaluating the spontaneous reactions, net glutamine utilization and net ammonia production by the cells could be estimated . It became evident that asparagine could support the growth of CHO cells as a stable substitute for glutamine . Then, a glucose fed-batch culture was grown on a glutamine free and asparagine supplemented medium . Because of (1) low glucose concentration, but (2) no glucose limitation and (3) low ammonia accumulation, the maximum total cell concentration reached 3.4 x 10(6) ml-1, which was 1.8 times greater than that in the control experiment (initial 1.15 g l-1 glucose and 0.29 g l-1 glutamine, and no glucose feed). J Biotechnol, 1990 Jul, 15(1-2), 101 - 111 Growth behavior of Chinese hamster ovary cells in a compact loop bioreactor: 1 . Effects of physical and chemical environments; Kurano N et al.; Chinese hamster ovary (CHO) cells were cultivated in a compact loop bioreactor using MEM-alpha medium supplemented with 10% fetal calf serum . Effects of physical and chemical environments, i.e., pH in the medium, stirring speed of impellers, temperature and partial pressure of oxygen (pO2) upon growth of suspended cells in the bioreactor were determined in batch cultures . Growth behavior was characterized by specific rates of growth (mu), glucose consumption (qG) and lactate production (qL), and the yield coefficients (cell yield from glucose, YX/G, and lactate yield from glucose, YL/G) . An effect of medium osmolality was also evaluated with T-flask monolayer cultivation . The best growth was observed at pH 7.6, 37 degrees C, 400 rpm, 50-100% saturation with oxygen and 320 mOsmol kg-1 . Corresponding to the previous work with a human melanoma cell line, the sophisticated cultivation and process control systems have been improved for CHO cells. J Antibiot (Tokyo), 1990 Jun, 43(6), 607 - 15 A54145, a new lipopeptide antibiotic complex: factor control through precursor directed biosynthesis; Boeck LD et al.; A54145 is a complex of new lipopeptide antibiotics produced by Streptomyces fradiae . Eight factors, containing four similar peptide nuclei in combination with three different fatty acid acyl side chains, have been isolated from the natural fermentation and characterized . The nuclei differ only in valine/isoleucine and glutamate/3-CH3-glutamate substitutions at one or both of two locations on the peptide ring . Prior deacylation of all four nuclei with Actinoplanes utahensis had permitted chemical reacylation of each nucleus with new fatty acid acyl chains for structure-activity relationship studies . In an effort to induce the native biosynthesis of preferred factors or analogs by S . fradiae, the effect of fatty acid precursors on the fermentation was examined . Many fatty acids were extremely toxic to S . fradiae, which limited experiments to slow, continuous feeding of the lipids in stirred bioreactors that were equipped for on-line respiration analysis by mass spectrometry . These studies determined that precursing with aliphatic fatty acids of various chain lengths did enhance the biosynthesis of factors containing specific fatty acid acyl side chains . Caprate, for example, increased the n-decanoyl-containing factors from the natural level of approximately 14% to approximately 80% . The percentage of factors containing branched-chain fatty acid acyl substituents was also increased, in shaken-flask studies, by enriching the medium with valine or isoleucine . These amino acids additionally enhanced the percentage of nuclei containing either valine or isoleucine. J Antibiot (Tokyo), 1990 Jun, 43(6), 587 - 93 A54145, a new lipopeptide antibiotic complex: discovery, taxonomy, fermentation and HPLC; Boeck LD et al.; A54145 is a complex of new lipopeptide antibiotics that inhibits Gram-positive bacteria and acts as a growth promotant for broiler chicks . Eight factors; A, B, C, D, E, F, A1 and B1; have been isolated and characterized . They contain four similar peptide nuclei, each of which is acylated with either an 2-decanoyl, n-decanoyl, or undecanoyl side chain . Taxonomic studies ascertained that the producing microorganism was a strain of Streptomyces fradiae . Fermentation studies determined that superior antibiotic yields were obtained in stirred bioreactors in a soybean flour-molasses medium employing a continuous glucose feed . These findings, interwoven with the selection of hyper-productive mutants, increased fermentation yields from less than 50 micrograms/ml to more than 1 mg/ml . An analytical HPLC system was developed for the identification and subsequent quantitation of each factor of the A54145 complex. Int J Artif Organs, 1990 Jun, 13(6), 365 - 9 Computer aided time-lapse video analysis of hepatocyte morphology during adhesion to cellulose membranes; Gerlach J et al.; An investigation was performed to demonstrate that time-lapse cinematography and computer aided video analysis of cell morphology is suitable to study and compare the characteristics of hepatocytes during the adhesion process to membranes . We chose to compare ordinary cellulose Cuprophan membranes and membranes coated with collagen or fibronectin . Striking differences between uncoated cellulose and fibronectin or collagen coating were seen in the cell count per square millimeter and adhesion behaviour . On the investigated uncoated Cuprophan the hepatocytes were found to attach but not to spread whilst on collagen coated Cuprophan most of the cells spread spherically, and on fibronectin coated membranes most of the cells flattened spherically or polygonally . Time-lapse video microscopy seems to be a valuable technique for assessing the morphologic behaviour of cells in a detailed and quantitative manner in order to improve the hepatocyte culture technique in bioreactors for hybrid systems. Arch Latinoam Nutr, 1990 Jun, 40(2), 147 - 93 {Chemical and biochemical characteristics of the microbial biomass}; Rolz C; The nutritional potential of microbial biomass products is determined by their chemical and biochemical characteristics . The same vary according to the microbial species, the source of nutrients employed for their growth, the operational mode of bioreactor and, finally, due to processing effects during growth or in the unit operations employed for its recovery . In this review, a detailed chemical description is given for those microbial biomass products from algae, bacteria, yeast and fungi, which have been either commercially produced or produced for demonstration purposes in pilot installations . Lastly, the effect of some operational parameters over the biomass chemical composition are illustrated in order to show general tendencies that have been experimentally observed, without a claim to be an exhaustive literature review of all aspects involved. J Biotechnol, 1990 Jun, 14(3-4), 377 - 92 Production of recombinant human interleukin-2 with BHK cells in a hollow fibre and a stirred tank reactor with protein-free medium; Ryll T et al.; For the production of recombinant human interleukin-2 (IL-2) two different culture processes, a 1-2 liter homogeneous stirred bubble-free aerated system and a dense cell hollow fibre bioreactor were compared . Cultivations were carried out with serum- or protein-free medium formulations . In the stirred culture 0.75 mg IL-2 were produced with 1 l of perfused medium at a maximum cell number of 3 X 10(10) . The product yield in the hollow fibre module was only 0.23 mg l-1 at a maximum cell number of 6 X 10(10) . In contrast to results with hybridoma or EBV-transformed cell lines, in which hollow fibre bioreactors showed comparable efficiency to perfused stirred tank reactors, the tissue-like cell density is disadvantageous as adherent cells tend to stick together leaving insufficient intercellular space for removal of product. J Biotechnol, 1990 Jun, 14(3-4), 345 - 61 Cell growth and enzyme synthesis of a mutant of Arthrobacter sp . (DSM 3747) used for the production of L-amino acids from D,L-5-monosubstituted hydantoins; Syldatk C et al.; A microorganism with the ability to form L-tryptophan from D,L-5-(3-indolyl-methyl)hydantoin (D,L-5-IMH) was isolated and identified as Arthrobacter sp . (DSM 3747) . After isolation of a mutant with high tryptophan production activity but low tryptophan degradation, cultural conditions were optimized to achieve high amounts of biomass with good specific activities concerning the enzymatic hydantoin-cleaving reactions . The ability of the microorganism to perform these bioconversions was found to be inducible by D,L-5-IMH as well as to be dependent on the presence of Mn2+ . The highest specific D,L-5-IMH-cleaving activity of the cells was observed in the exponential phase of growth . The addition of yeast extract to the mineral salts medium was found to be essential for obtaining biomass concentrations of about 25 g l-1 cell dry mass by bioreactor cultivations . In order to obtain a constantly high growth rate, feeding of the C-source was pO2-controlled . The inducer D,L-5-IMH had to be continuously fed to prevent a decline of the L-tryptophan-forming enzyme activities, because it was subjected to degradation with the enzymes induced and higher concentrations of D,L-5-IMH aggravated the growth significantly . The synthesis of the enzymes was also inducible, when inducer and Mn2+ were not added until the late growth phase . Using this process, the consumption of D,L-5-IMH was reduced remarkably . So, under these conditions biomass concentrations of 25 g l-1 cell dry weight with a specific enzymatic activity of 0.20 mmol g-1 h-1 (tryptophan per dry mass per time) could be obtained within 13 h . Using 1 g l-1 of the chemically modified inducer D,L-5-(3-indolylmethyl)-3-N-methylhydantoin, which was not degradable by the microorganisms, a biomass concentration of 28 g l-1 cell dry weight with a specific activity of 0.34 mmol g-1 h-1 (tryptophan per dry mass per time) could be obtained within 28 h. Biomed Chromatogr, 1990 May, 4(3), 123 - 7 A chemiluminometric method for NADPH and NADH using a two-enzyme bioreactor and its application to the determination of magnesium in serum; Tabata M et al.; Chemiluminometric methods are described for the automated flow injection analysis of NADPH and NADH using an immobilized enzyme column reactor and serum magnesium . This application is for the clinical analysis of NADPH and NADH . The reactor for NADPH and NADH contains immobilized L-glutamate dehydrogenase and L-glutamate oxidase, and that for serum magnesium immobilized hexokinase, glucose-6-phosphate dehydrogenase, L-glutamate dehydrogenase and L-glutamate oxidase . When the sample is introduced into the four-enzyme bioreactor, hydrogen peroxide is produced in proportion to the concentration of serum magnesium by the successive reactions . A co-immobilized hexokinase/glucose-6-phosphate dehydrogenase/glutamate dehydrogenase column reactor gave better efficiency compared with an enzyme column which was prepared by packing co-immobilized hexokinase/glucose-6-phosphate dehydrogenase and immobilized glutamate dehydrogenase to make two layers . Magnesium in serum was determined with 1 microL of the sample without carry-over and for an assay time of approximately 15 s . The present method is sensitive (detection limit 0.1 nmol) because Mg2+ is recycled in a column, and gives perfect linearity of the data up to 3.0 mmol/L with satisfactory precision, reproducibility, and accurate reaction recoveries. J Parenter Sci Technol, 1990 May-Jun, 44(3), 113 - 7 Operational aspects of bioreactor contamination control; Perkowski CA; The contamination-free operation of a bioreactor demands constant attention to details . Assuming a well-designed and validated system exists, contamination control requires a skilled operating staff, clear and concise standard operating procedures, ongoing operations review and training, thorough cleaning of equipment, and an effective preventative maintenance program . This paper highlights basic operational aspects of contaminant-free bioreactor operation from inoculum development to bioreactor harvesting. Int J Artif Organs, 1990 May, 13(5), 316 - 20 The synthesis of L-tryptophan degrading bioreactors; Schmer G et al.; To design a bioreactor for removing the potential cancer nutrient L-tryptophan from blood, the L-tryptophan degrading enzyme tryptophan side chain oxidase (TSO) was chemically bound to glutaraldehyde activated gamma amino silane silica and to Zetaffinity microcolumns consisting of a glutaraldehyde activated polyacrylic-cellulose copolymer . Five experiments were carried out in sheep and six experiments in rabbits using a closed circuit plasmapheresis bioreactor system . L-tryptophan in sheep was degraded by the silica bioreactor in a single pass to undetectable levels as measured by high performance liquid chromatography (HPLC) . Zetaffinity bioreactors degraded L-tryptophan in rabbits to more than 95% in a single pass . Whole blood L-tryptophan levels changed little throughout the experiment indicating a vast extravascular tryptophan pool . Enzyme leakage from the bioreactor was less than 10(-5) IU TSO per ml plasma . The procedures were tolerated well by the animals without any change in vital signs. Cytotechnology, 1990 May, 3(3), 301 - 7 Use of lactate dehydrogenase release to assess changes in culture viability; Racher AJ et al.; This study reports the use of lactate dehydrogenase release to monitor changes in culture viability in flask culture and fixed bed, porosphere bioreactor systems . Lactate dehydrogenase release shows good agreement with increase in non-viable cell numbers and decline in glucose utilisation in flask cultures . Studies with the immobilised system show that lactate dehydrogenase release can detect loss of viability which is not always indicated by a decrease in glucose utilisation . The data show that culture viability in a repeated-feed-and-harvest system is influenced markedly by both a) the medium change regime itself and b) the use of an immobilised bioreactor compared to a flask system for the same medium change regime. Biotechnol Prog, 1990 May-Jun, 6(3), 220 - 4 Production of monoclonal antibodies by hybridoma cells in a flat sheet membrane bioreactor; Hagedorn J et al.; The purpose of this study was to investigate hybridoma growth and monoclonal antibody formation in a flat sheet membrane bioreactor . The effects of several different molecular weight cutoff membranes on growth and antibody formation were investigated . Nutrient and toxic product diffusion through the membranes were quantified, and the kinetic and physical constants of the system were determined. J Biotechnol, 1990 May, 14(2), 211 - 20 The membrane bioreactor with coenzyme recycling system; Ikemi M et al.; Much attention has been paid to membrane bioreactors, especially to the newly developed charged membrane bioreactor (CMBR) for recycling the native form of the coenzyme NAD(P)H . Charged membranes with anionic groups effectively retained the free nicotinamide coenzyme due to the electrostatic repulsion between membrane and coenzyme . The capability of the CMBR was demonstrated by the continuous production of sorbitol using a multi-enzyme system of NADPH-dependent aldose reductase and glucose dehydrogenase . Several important features of the CMBR were elucidated by a theoretical model of coenzyme turnover. J Biotechnol, 1990 May, 14(2), 169 - 78 Immobilization of biocatalysts with poly(vinyl alcohol) supports; Ichijo H et al.; Two polymer materials, poly(vinyl alcohol) (PVA) superfine fibers and photocrosslinkable PVA bearing styrylpyridinium groups, have been developed to immobilize biocatalysts . The former has a large surface consisting of relatively large-size pores and the fibers can immobilize a large amount of biocatalyst on their surface by ionic interaction . The latter entraps many kinds of biocatalysts by cyclodimerization caused by visible light irradiation . The biocatalysts on/in these supports maintain high activity and thermal stability . These materials can easily be formed into various shapes suitable for various applications . A new bioreactor system was constructed for evaluating a variety of biocatalysts and supports. Biotechniques, 1990 Apr, 8(4), 414 - 22 Large-scale production of monoclonal antibodies in defined serum-free media in airlift bioreactors; Petrossian A et al.; Forty- and ninety-liter airlift bioreactors have been used successfully to grow hybridoma cell lines in chemically defined serum-free media . In the airlift bioreactor, hybridoma cell growth and monoclonal antibody productivity are comparable to that obtained by conventional cell culture . At sparging rates of 0.60-1.20 vvh (volume of sparged gas per bioreactor volume per hour), the airlift bioreactor achieves rapid mixing and adequate oxygen mass transfer . Foaming is minimal and inconsequential for serum-free media and media supplemented with 5%-10% fetal bovine serum . The use of serum-free medium facilitates monoclonal antibody purification and enhances the purity of the final MAb product. J Surg Res, 1990 Apr, 48(4), 379 - 82 Development of bioartificial liver: bilirubin conjugation in Gunn rats; Arnaout WS et al.; We developed a novel bioartificial liver using microcarrier-attached hepatocytes and a bioreactor . The bioreactor consists of an intracapillary chamber made up of porous (0.2 micron) cellulose acetate hollow fibers enclosed in a polycarbonate module forming an extracapillary chamber . Cryopreserved (-80 degrees C, 3 weeks) microcarrier-attached hepatocytes (3-4 X 10(7} were inoculated into the extracapillary chamber . The bioartificial liver, containing either microcarrier hepatocytes (n = 6) or microcarriers alone (n = 5); was attached to adult Gunn rats via cannulas in the aorta and inferior vena cava . Bile samples were collected before and at hourly intervals after attachment to the bioartificial liver . The same animal model was used to demonstrate de novo conjugation of free bilirubin by the bioartificial liver (n = 3) following systemic administration of unconjugated {3H}bilirubin . Bile was analyzed for bilirubin mono- and diglucuronides by high-performance liquid chromatography and confirmed by digestion with beta-glucuronidase and cochromatography with normal rat bile . A progressive increase in the concentration of bilirubin monoglucuronide and bilirubin diglucuronide in bile was seen as early as 30 min and lasted up to 4 hr following attachment to a bioartificial liver containing microcarrier hepatocytes (3.53 +/- 0.68 to 8.07 +/- 0.85 microM; P less than 0.01) . Approximately 22% of the radiolabeled bilirubin excreted in bile was seen in the form of bilirubin conjugates, no radioactivity was seen in the free bilirubin fraction . In conclusion, we developed a bioartificial liver using microcarrier hepatocytes which carry out an important differentiated liver function which results in partial correction of a specific metabolic liver defect, i.e., conjugation of bilirubin. Biotechnology (N Y), 1990 Apr, 8(4), 327 - 30 Quantitative flow measurements in bioreactors by nuclear magnetic resonance imaging; Hammer BE et al.; We have developed nuclear magnetic resonance (NMR) flow imaging techniques to measure fluid flow in a cell-free hollow fiber bioreactor (HFBR) . Using 1H NMR we track the motion of protons and obtain velocity distributions as a function of position and time . These measurements enable the visualization of flow patterns needed for module design and for establishing desired operating conditions . Uneven flow in the cell-containing region of an HFBR can result in concentration gradients and uneven cell distribution that may lead to reduced cell viability . Results from this non-invasive method could be used to design more efficient cell bioreactors or membrane separation devices. J Biotechnol, 1990 Apr, 14(1), 81 - 7 An automated spectrophotometric flow-injection procedure for the determination of cellulase activity in bioreactor preparations; Worsfold PJ et al.; A spectrophotometric procedure for the determination of cellulase activity in precipitated bioreactor preparations and culture filtrates is described . It is based on the determination of reducing sugar produced by the action of the enzyme on carboxymethylcellulose . The reducing sugar is derivatized with p-aminobenzoyl-hydrazide and permits a limit of detection of 0.1 U ml-1 cellulase in the presence of background sugar, with a sampling rate of 5 h-1 . The method can readily be applied to the determination of any carbohydrase acting on soluble substrates and producing reducing sugars, e.g . amylase, dextranase, xylanase, glucanase and polygalacturonase. Biochem Cell Biol, 1990 Mar, 68(3), 661 - 8 Relationship of alcohol production to lipid composition of yeast in a continuous flow bioreactor; Gil GH et al.; Saccharomyces cerevisiae was cultivated in a controlled aerated, dual-stage (column), continuous flow bioreactor in a hybrid free-cell and immobilized-cell state . The yeast cells maintained an ethanol concentration of 58-64 and 91-98 g/L in stages I and II, respectively . The lipid composition of the cells cultivated under these conditions was correlated to the effects of aeration by interrupting the aeration on days 113 and 266 of continuous operation . Under conditions of aeration or nonaeration, an alternating increase and decrease in the contents of squalene, sterols, and fatty acids of the respiratory-competent and -deficient unattached free cells was observed . The cellular free lipid compositions of the immobilized cells in the aerated and nonaerated conditions were similar and characteristic of respiratory-deficient cells with the exception of the immobilized cells exposed to a higher ethanol concentration (stage II) . These cells contained a broader range of sterol components and increased levels of unsaturated fatty acids than immobilized cells at a lower ethanol concentration (stage I) . The neutral lipid to phospholipid ratio decreased for respiratory-deficient cells with phosphatidylethanolamine and phosphatidylinositol being the principal phospholipids . The data demonstrated the essentiality of the hybrid bioreactor design for continuous long term performance and the importance of maintaining specific yeast lipid constituents for continuous high alcohol productivity. Biotechnol Prog, 1990 Mar-Apr, 6(2), 142 - 8 Structural features of nonionic polyglycol polymer molecules responsible for the protective effect in sparged animal cell bioreactors; Murhammer DW et al.; The nonionic surfactant Pluronic F-68 polyol is commonly used to protect cultured animal cells from the detrimental effects of sparging . In this study we investigated the structural features of the Pluronic F-68 molecule responsible for this protective behavior . Poly(oxyethylene)-poly(oxypropylene) block copolymer polyols of various molecular weights and percentages of hydrophobe (poly(oxypropylene}, including both Pluronic and reverse Pluronic polyols, were considered . The potential toxicity of these agents was examined in the absence of sparging (i.e., in spinner flasks) by using the attachment-independent Sf9 insect cell line as a model system . Each polyol resulted in one of three distinct types of behavior in these spinner flask experiments: (1) cells lysed at an exponential rate, (2) inhibition of cell growth (i.e., no net cell growth), or (3) uninhibited cell growth . It was then shown that all of the Pluronic and reverse Pluronic polyols that did not inhibit cell growth provided protection from sparging in the bioreactors used in this study; thus, finding a polyol that protected cells was synonymous with finding one that did not inhibit cell growth . The ability of these polyols to protect animal cells in sparged bioreactors was found to correlate well with the hydrophilic-lipophilic balance (HLB) . Those polyols with the largest HLB values were found to be protective agents . These poly(oxyethylene)-poly(oxypropylene) polyols were also shown to be more effective protective agents than pure poly(oxyethylene); thus, the presence of the hydrophobe (poly(oxypropylene} is important in their ability to serve as protective agents. Trends Biotechnol, 1990 Mar, 8(3), 71 - 8 Alginate as immobilization matrix for cells; Smidsrod O et al.; In recent years, entrapment of cells within spheres of Ca2+ alginate has become the most widely used technique for immobilizing living cells . This versatile method includes applications ranging from immobilization of living or dead cells in bioreactors, immobilization of plant protoplasts for micropropagation and immobilization of hybridoma cells for production of monoclonal antibodies, to entrapment of animal cells for implantation of artificial organs . This review evaluates the potential of this method on the basis of the current knowledge of structural and functional relationships in alginate gels. J Biotechnol, 1990 Mar, 13(4), 315 - 23 Continuous itaconic acid production by immobilized biocatalysts; Kautola H et al.; The continuous itaconic acid production from sucrose with Aspergillus terreus TKK 200-5-3 mycelium immobilized on polyurethane foam cubes was optimized in column bioreactors using statistical experimental design and empirical modelling . The highest itaconic acid product concentration calculated on the basis of the obtained model was 15.8 g l-1 in the investigated experimental area, when sucrose concentration was 13.5%, aeration rate 150 ml min-1 and residence time 178 h . From sucrose with immobilized A . terreus TKK 200-5-3 mycelium itaconic acid production was stable for at least 4.5 months in continuous column bioreactors . In comparison, using glucose as substrate and immobilized A . terreus TKK 200-5-1 mycelium as biocatalyst similar stability was obtained with higher product concentration . The omission of copper sulphate from the production medium gave the highest itaconic acid product concentration (26 g l-1) from 9% glucose with 0.25% ammonium nitrate and 0.095% magnesium sulphate. J Immunol Methods, 1990 Feb 20, 127(1), 29 - 37 Culture of human tumor infiltrating lymphocytes in hollow fiber bioreactors; Knazek RA et al.; Human tumor infiltrating lymphocytes (TIL) from metastatic melanoma of six patients were grown using a new hollow fiber bioreactor system . After inoculating 0.35-10 X 10(8) TIL into the extra-fiber space (EFS), each Cellmax bioreactor was perfused with AIM-V medium, supplemented with rIL-2 . The cells subsequently expanded 124-1170-fold to yield 1.5-5.4 X 10(10) TIL over a 14-32 day period . TIL were flushed from the EFS using 200 ml medium and possessed an average viability = 91% . The phenotype and the autologous tumor cell lytic capacity of these TIL were similar to those of TIL grown in the currently used gas-permeable culture bags . Tissue culture media use averaged 4.3 liters/10(10) TIL harvested . The TIL of one patient were re-expanded twice from cells remaining within the same bioreactor after harvest suggesting that one bioreactor cartridge could be used for repetitive, periodic studies . An estimated 80% decrease in technical time expended and in incubator space requirements were realized using this methodology . Cell culture on hollow fibers appears to be a useful method for producing large quantities of primary human lymphocytes for experimental, and perhaps, therapeutic needs. J Clin Microbiol, 1990 Feb, 28(2), 283 - 6 Growth of Vero E-6 cells on microcarriers in a cell bioreactor; White LA et al.; Minimum essential medium supplemented with either 7% fetal bovine serum or 2% fetal bovine serum and 1.5% low protein serum replacement (Sigma Chemical Co., St . Louis, Mo.) factor was used to evaluate the growth of Vero 76 cells (E-6 clone) in a cell culture bioreactor . Three different microcarriers, collagen-coated polystyrene (Kontes Life Sciences Products, Vineland, N.J.), Gelibead (Hazelton Research Products, Inc., Lenexa, Kans.), and Cytodex 3 (Pharmacia Fine Chemicals, Piscataway, N.J.), were used to compare the propagation of these anchorage-dependent cells . The number of viable cells recovered during three harvests over an 11-day incubation period was evaluated . The Vero E-6 cells grew equally well with both media . When the collagen-coated dextran microcarriers (Cytodex 3) were used, better cell attachment and higher-density growth were obtained and 5.5 x 10(8) to 7.0 x 10(8) cells were recovered from the system. Zhonghua Min Guo Wei Sheng Wu Ji Mian Yi Xue Za Zhi, 1990 Feb, 23(1), 75 - 88 {Large-scale production of monoclonal antibodies using hollow fiber bioreactor}; Chen BS et al.; Development of large-scale monoclonal antibody production using industrial scale hollow fiber bioreactor is described . Hybridoma cell lines H505AC and A306AA were cultivated in the hollow fiber perfusion bioreactor with a total fiber surface area of 7.2 m2 (6 x 1.2 m2) to produce anti-hepatitis B surface antigen (anti-HBsAg) monoclonal antibody IgM and anti-alpha-fetal protein (anti-AFP) monoclonal antibody IgG . The highest anti-HBsAg IgM productivity obtained during 49 days cultivation of H505AC was 0.135 g/day and the total accumulated IgM was 1.90 g . Results from the cultivation of A306AA in the hollow fiber module for 23 days showed the highest anti-AFP IgG productivity and the total accumulated IgG were 0.672 g/day and 7.21 g, respectively. Adv Biochem Eng Biotechnol, 1990, 42, 13 - 26 Large-scale animal cell cultures: design and operational considerations; Ramasubramanyan K et al.; The manufacture of biologicals, especially proteins, using large-scale culture of animal cells is becoming popular . There is a need for a rational approach to the design and scale-up of bioreactors for these applications . The ultimate requirement of any scale-up strategy should be to preserve the biological activity of these high-value molecules . With this as the central theme, the design and operation of animal cell processes has been discussed . Equal importance has been given to both the biological and the engineering aspects which need to be considered for a successful scale-up . An integrated systems approach has been stressed. Biomater Artif Cells Artif Organs, 1990, 18(4), 523 - 8 Bioreactors in medicine; Hoffman AS; The use of immobilized enzyme reactors in medicine is briefly reviewed in this presentation . Emphasis is placed on the recent and emerging technology involved in development and clinical applications of such devices. Ann N Y Acad Sci, 1990, 589, 399 - 422 Bioreactor development for production of viral pesticides or heterologous proteins in insect cell cultures; Shuler ML et al.; The insect cell-baculovirus expression system has significant potential for producing proteins requiring some degree of posttranslational modification . T . ni cells appear to be as good a host as S . frugiperda cells for heterologous protein production as demonstrated by production of beta-galactosidase . Attachment-dependent cells of T . ni can be effectively cultured in a packed-bed reactor using glass beads . When cell in such a reactor were infected, they produced 35% of the total protein as beta-galactosidase . No cell detachment was observed even 70 h postinfection . A model of viral entry has been proposed and tested. Bull Math Biol, 1990, 52(6), 785 - 96 A nonlinear three-compartment model for the administration of 2',3'-dideoxycytidine by using red blood cells as bioreactors; Solimano F et al.; A non-linear three-compartment model is proposed to describe a new strategy for the administration of 2',3'-dideoxycytidine (ddCyd) in the treatment of HIV infections . The drug is injected after having been encapsulated in a non-diffusible form (ddCMP) into erythrocytes . Numerical solutions show that by this treatment the highest ddCyd blood concentration is strongly reduced and in turn its toxicity, while long-lasting therapeutic effect is assured . The model is compared with experimental data in vitro. Acta Biochim Biophys Hung, 1990, 25(1-2), 9 - 16 Factors influencing the operation of a vertical bioreactor segmented with perforated plates; Buzas Z et al.; Factors influencing the operation of a vertical bioreactor segmented with perforated plates supporting immobilized yeast cells were studied . It was found that the most important factors are the length-diameter (L/D) ratio of the reactor and the dilution rate . It was supposed that the optimal L/D ratio is about 1 . The operation of the reactor was more favourable at a low liquid phase-solid phase ratio . The spatial distribution of the biocatalyst had only a slight, if any effect . The periodically changed direction of feed flow has no improving effect on the fermentation process. Dev Biol Stand, 1990, 71, 65 - 71 Tissue culture in hollow-fibre systems: implications for downstream processing and stability analysis; Tiebout RF; Murine hybridoma cells, not adapted to low-protein or serum-free culture media, were grown in a hollow-fibre bioreactor or a stirred-tank perfusion system . In both situations, the serum content of the medium was gradually decreased during the process . The harvest obtained from the hollow-fibre reactor contained a much higher concentration of monoclonal antibody (MAb) as compared to the supernatant harvested from the stirred-tank perfusion system . Moreover, the production rate of the cells grown in the hollow-fibre reactor system was not affected by decreasing the concentration of serum in the medium to as low as 0.5% while the same cell line required 2% of serum in the stirred-tank reaction system . Consequently, the ratio of the concentration of MAb over serum proteins in the tissue culture supernatant derived from the hollow-fibre system was much higher than the one present in the harvest derived from the stirred-tank perfusion system . To study the stability of the cell mass immobilized in the hollow-fibre perfusion system, culture supernatants were tested for the presence of immunoglobulin heavy chain isotype switch variants at various intervals after initiation of culture from the cell bank . The implications of the features of hollow-fibre bioreactor systems for the production of MAb for clinical applications are discussed. Ciba Found Symp, 1990, 154, 157 - 70; discussion 170-4 An economic and technical assessment of the use of plant cell cultures for natural product synthesis on an industrial scale; Fowler MW et al.; Plant cell cultures may be used as an alternative source of established natural products, as a source of novel 'lead' compounds or as a source of enzymes for modification of precursors . Only a few plant cell processes are operating commercially and their performance characteristics are industrial secrets . The economic aspects of natural product synthesis in plant cell cultures are presented on the basis of data derived from work on a pilot plant with bioreactors of 5-80 litres in which cells are grown in batch liquid culture . Cost analysis shows that the labour costs of operating plant cell culture processes are much higher than those for microbial processes, which reflects the longer process times of plant systems . These can be reduced by increasing the cell growth rate, the biomass yield and/or the product yield . Higher yields can be obtained by optimizing media conditions, but there are no standard guidelines for this . Each system has to be developed individually . Reducing the number of production runs a year, usually by increasing the number of days for which each batch of cells is synthesizing product, can markedly decrease costs . Economic assessment of the viability of production in plant cell cultures must consider not only production costs but also the expected market price of the product and the volume of sales. Bioprocess Technol, 1990, 10, 71 - 92 Large-scale animal cell culture: a biological perspective; Oka MS et al.; It is generally recognized that no one cell culture system can be universally applied to all cell types commonly used for biopharmaceutical manufacture . The analogous concept that no single cell type may be useful for the expression of all biopharmaceutical products may also gain credence in the biotechnology community . It may be that like specialized bioreactors, there will come to exist a variety of cell types that will be used for the production of different types of biopharmaceutical products . In addition, it may not be enough in the future just to demonstrate the stability of expression of the amino acid backbone of the protein only; the carbohydrate portion of the molecule may become the subject of real scrutiny . Questions such as how the carbohydrate side chain affects the performance of the molecule in vivo are being asked of more DNA constructs . The next question becomes, how can we control the expression of carbohydrate moieties on the molecule? Such questions are in the future of the biotech manufacturing field . Aside from those examples mentioned above dealing with the insertion of receptors, other more subtle attempts at modifying cellular metabolism are taking place . It was reported at a recent meeting that the sialyltransferase gene was inserted into a CHO line which did not normally express this enzyme (116) . The transfected line was capable of expressing the transferase and, more importantly, the enzyme functioned correctly in sialylating glycoproteins . Other very complex relationships exist between the substratum and the cell that could have very direct consequences on culture maintenance . For example, researchers recently published results indicating that collagenase synthesis and secretion is stimulated in rabbit fibroblasts by autocrine factors . They determined that these autocrine proteins had sequence homology to serum amyloid-A and beta-2-microglobulin . It may be that using serum supplements in the medium in those systems that couple fibroblast and collagen substratum may not be prudent, especially for long-term culture . The traditional selection of a cell type for expressing heterologous proteins has generally been limited to the more "common" cell types such as CHO cells, C127 cells, and myeloma cells . In many cases these cell types were selected because there was a great deal of preexisting literature on the cell type (i.e., "cookbook" methods of transfection for the cell) or the cell was simply being carried in the lab at the time the effort was made to express a biopharmaceutical product.(ABSTRACT TRUNCATED AT 400 WORDS) Bioprocess Technol, 1990, 10, 597 - 618 Large-scale propagation of insect cells; Vaughn JL et al.; Cultured insect cells have many uses in agriculture and medicine . They can be used in the diagnosis and isolation of a number of viruses infecting both animals and plants and for the laboratory study of these viruses . Large-volume culture of insect cells has been envisioned as a way of producing viruses for use in controlling insect pests and for the production of viral antigens for vaccine preparations . Recently they have become a potentially valuable way of producing a variety of proteins for human and veterinary medicine using the genetically engineered baculovirus expression vectors . The development of satisfactory cell lines and culture methods has proceeded at a slow, irregular pace, inhibited by the lack of knowledge of the physiology of the insect, its small size, and often by the lack of consistent, adequate support for the necessary developmental research . However, now that the basic culture systems are available, cell lines have been developed or can easily be developed for most needs . Suitable media are available and recent developments in refining existing media formations have resulted in low-cost media containing little protein to interfere with down-stream processing of cellular metabolites . Future developments are likely to further improve the media formulations and lower the cost . Technical problems relating to oxygen demand and cell fragility that inhibited the continued development of large-volume culture systems beyond the laboratory a few years ago now appear to be solved or at least are solvable . The successful culture of the Spodoptera cells in bioreactors of 40-liter capacity indicates that means of producing insect cells or their metabolic products on a commercial scale can be made economically feasible. J Chem Technol Biotechnol, 1990, 49(4), 357 - 79 An immobilized cell bioprocess for the removal of heavy metals from aqueous flows; Macaskie LE; Microorganisms can be used to remove toxic heavy metals from liquid industrial wastes . In addition to the chemical toxicity of many of the latter, the production of long-lived nuclides from nuclear power programmes has introduced additional radiotoxicological hazards . Associated problems of the presence of contaminating, non-metal co-pollutants and the presentation of dilute, high-volume wastes have received little attention . Traditional biotechnological waste treatments have relied either on the use of non-living biomass ('biosorption') or on the accumulation of metals by living cells with the associated problems of metal toxicity effects and the requirements for cell viability or growth . Identification of an enzymically-mediated metal accumulation step can permit decoupling of cell growth from metal accumulation . Using pre-grown biomass immobilized in a flow-through filter ('bioreactor') the metal-accumulative bioprocess can be described accurately applying traditional Michaelis-Menten kinetics . The effect of co-pollutants can be then quantified in order to run the bioreactor in the most efficient way. J Chem Technol Biotechnol, 1990, 49(4), 331 - 43 Biosorption of radionuclides by fungal biomass; White C et al.; Four kinds of bioreactor were evaluated for thorium removal by fungal biomass . Static-bed or stirred-bed bioreactors did not give satisfactory thorium removal probably because of poor mixing . An air-lift bioreactor removed approximately 90-95% of the thorium supplied over extended time periods and exhibited a well-defined breakthrough point after biosorbent saturation . The air-lift bioreactor promoted efficient circulation and effective contact between the thorium solution and the mycelial pellets . Of several fungal species tested, Rhizopus arrhizus and Aspergillus niger were the most effective biosorbents with loading capacities of 0.5 and 0.6 mmol g-1 respectively (116 and 138 mg g-1) at an inflow thorium concentration of 3 mmol dm-3 . The efficiency of thorium biosorption by A . niger was markedly reduced in the presence of other inorganic solutes while thorium biosorption by R . arrhizus was relatively unaffected . Air-lift bioreactors containing R . arrhizus biomass could effectively remove thorium from acidic solution (1 mol dm-3 HNO3) over a wide range of initial thorium concentrations (0.1-3 mmol dm-3) . The biotechnological application and significance of these results are discussed in the wider context of fungal biosorption of radionuclides. Cytotechnology, 1990 Jan, 3(1), 89 - 93 Serial cultivation of suspended BHK 21/13 cells in serum-reduced and serum-free medium supplemented with various membrane protective agents; Gurhan SI et al.; Suspended BHK 21/13 cells were cultivated in 6M medium supplemented with PVP, bovine serum, LAH, YE, choline chloride and inositol at several concentrations . The maximum working capacity of the bioreactors was 400 ml and the experiments were run for 40 days . The growth promoting effects of each substrate were determined by calculation of generation numbers (n) in each culture . Viability testing and morphological detection of the cells were realized by the trypan blue exclusion method . As a result, the membrane protective effect of PVP, as suggested by some authors, was confirmed and it was estimated that the positive effects of PVP on cell propagation in cultures were due to its protective activities. J Biotechnol, 1990 Jan, 13(1), 29 - 46 High level expression of interleukin-1 beta in a recombinant Escherichia coli strain for use in a controlled bioreactor; Arthur PM et al.; A recombinant bacterial strain for the large scale production of human interleukin-1 beta (IL-1 beta) was constructed . The lambda Pr and the tryptophan systems were compared for efficiency of transcription and regulation . The efficiency of IL-1 protein production from these constructs was analyzed . Enhanced protein synthesis was achieved by the fusion of lambda Pr promoter sequences with trp leader sequences which included the trp RBS . A strain (JM101) was selected for use as a host and tested in a one liter bioreactor . A growth and induction regimen was established for use in bioreactors which results in the accumulation of 0.75-0.95 g l-1 of recombinant IL-1. Biotechnology (N Y), 1990 Jan, 8(1), 47 - 51 Use of the Escherichia coli SSB gene to prevent bioreactor takeover by plasmidless cells; Porter RD et al.; Reactor takeover by plasmidless cells is a major problem encountered when producing proteins from plasmid-borne genes in genetically engineered bacteria . We have approached this problem by deleting the essential ssb gene from the Escherichia coli chromosome and placing it on a plasmid . Plasmidless cells do not accumulate even after growing such strains under non-selective continuous culture conditions for extended periods of time . Other ssb-containing plasmids can be readily introduced into this E . coli strain by a plasmid-displacement technique . Using this system, we have achieved very high levels of beta-lactamase production in continuous culture without selective pressure. FEMS Microbiol Rev, 1989 Dec, 5(4), 277 - 99 Microbiological methods for the cleanup of soil and ground water contaminated with halogenated organic compounds; Morgan P et al.; There is growing interest in the enhancement of microbial degradative activities as a means of bringing about the in situ cleanup of contaminated soils and ground water . The halogenated organic compounds are likely to be prime targets for such biotechnological processes because of their widespread utilisation and the biodegradability of many of the most commonly used compounds . The aim of this review is to consider the potential for microbiological cleanup of haloorganic-contaminated sites . The technologies available involve the provision of suitable environmental conditions to facilitate maximum biodegradation rates either in the subsurface or in on-site bioreactors . Methodologies include the supply of inorganic nutrients, the supply of oxygen gas, the addition of degradative microbial inocula and the introduction of co-metabolic substrates . The potential efficiencies and limitations of the methods are critically discussed from a microbiological viewpoint with respect to substrate degradability and population responses to supplementation. Experientia, 1989 Dec 1, 45(11-12), 1055 - 61 Application of living microbial cells entrapped with synthetic resin prepolymers; Fukui S et al.; Living and growing microbial cells were immobilized by entrapping in synthetic resin gels prepared from their prepolymers, and used in the production of various useful substances . The production of the desired metabolites and also both the activity and the stability of the catalytic systems were seriously affected by the physico-chemical properties of the prepolymers, and those of the resin gels subsequently formed, such as gel network, hydrophilicity-hydrophobicity balance and ionic nature, as well as by the type of bioreactors . Hydroxylation of steroids and production of antibiotics, polypeptides and other biologically active substances, and the effects of gel properties on them are discussed as examples. Int J Artif Organs, 1989 Dec, 12(12), 788 - 92 Use of hepatocytes in adhesion and suspension cultures for liver support bioreactors; Gerlach J et al.; Hepatocyte cultivation in bioreactors for hybrid liver support systems is possible under two conditions: attached to a substrate like membranes or microcarriers or in suspension culture . To compare the ammonia metabolism of hepatocytes cultivated under these two conditions, cultures of primary seeded rat hepatocytes were cultivated either attached to collagen coated tissue culture plastic or as a suspension culture . During the time course of culture, the ability of hepatocytes to reduce the ammonia content of the medium decreased in both adhesion and suspension cultures, though to different extents . In suspension cultures, ammonia content was reduced from 350 microM to about 100 microM (day 4) and to about 180 microM (day 6) . No significant reduction was seen on day 8 of culture . In contrast, hepatocytes attached to collagen coated dishes remained viable and functional for at least 8 days after plating, reducing ammonia content from 350 microM to 70 microM (day 4), 90 microM (day 6) and 180 microM (day 8) . The period of useful metabolism of hepatocytes in bioreactors for hybrid liver support systems appears to depend on the culture conditions. Biochem Biophys Res Commun, 1989 Oct 16, 164(1), 446 - 52 Human red blood cells as bioreactors for the release of 2',3'-dideoxycytidine, an inhibitor of HIV infectivity; Magnani M et al.; 2',3'-Dideoxycytidine (ddCyd) is one of the most potent antiviral nucleosides for killing the human immunodeficiency virus (HIV) . ddCyd is currently used in the treatment of severe HIV infections but due to its rapid clearance it must be administered to patients every 4 h reaching concentrations that are toxic . We have synthesized 2',3'-dideoxycytidine-5'-phosphate (ddCMP) as a prodrug, encapsulated it in human erythrocytes and found that it is dephosphorylated by endogenous pyrimidine nucleotidases and subsequently released by the cells as ddCyd . Encapsulated ddCMP does not affect erythrocyte metabolism and was not deaminated by cytidine deaminase . The dephosphorylation reaction has an apparent Km of 6mM, an optimum pH of 6.8 and is not inhibited by ATP or 2,3-bisphosphoglycerate . The efflux of ddCyd from the erythrocyte is a linear function of ddCyd concentration and relatively insensitive to nucleoside transporter inhibitors suggesting that ddCyd permeates the erythrocyte membrane predominantly by nonfacilitated diffusion . Thus, ddCMP-loaded erythrocytes might be used as endogenous bioreactors for ddCyd delivery in the treatment of HIV infection. Anal Biochem, 1989 Sep, 181(2), 209 - 11 Quantification of attached cells in tissue culture plates and on microcarriers; Margis R et al.; A method for quantification of anchorage-dependent cells in culture on plane surfaces or on microcarriers is proposed . It is based on Coomassie brilliant blue R-250 adsorption, followed by elution of the dye and measurement by spectrophotometry at 595 nm . A linear correlation (r = 0.988 to 0.996) was observed between absorbance and cell number along a large range of cell densities . This technique may be used for monitoring cell growth, from seeding of initial inoculi to scaling up of cultures in bioreactors. Int J Artif Organs, 1989 Aug, 12(8), 539 - 43 Monitoring the kinetics of glucose transfer across a bioreactor membrane with a glucose sensor; Velho G et al.; Bioreactors for cell culture, in which hollow fibers are sealed into a protective jacket, cells are seeded in the fibers' outer surface and a culture medium circulates through the fibers, have been proposed as a bioartificial pancreas . We used a needle-type glucose sensor to study the kinetics of glucose transfer across the membrane of one such device . The glucose transfer was found to be dependent on the flow rate of the circulating medium, which suggests the involvement of an ultrafiltration flux across the membrane . The glucose concentration was heterogeneous within the cell compartment . This heterogeneity, and the delay in transmission of changes in glucose concentration from the circulating medium to the cell compartment, can be ascribed to the large volume of the compartment . The design of these bioreactors should therefore be modified, in order to meet the requirements of glucose transfer kinetics of a bioartificial pancreas. Semin Nucl Med, 1989 Jul, 19(3), 202 - 20 Practical considerations in the production, purification, and formulation of monoclonal antibodies for immunoscintigraphy and immunotherapy; Bogard WC Jr et al.; Issues associated with the large-scale production of monoclonal antibodies for pharmaceutical applications are examined . The development of a commercial monoclonal antibody production process involves much more than just scaling-up the laboratory process and making it cost-effective . It involves establishing the hybridoma cell bank with cells that are free of adventitious agents such as viruses and mycoplasma, that have stability in continuous culture for antibody-production rate and cell viability, and that do not have unusual or expensive media requirements . The style and mode of operation of the bioreactor used to produce the antibody must be explored . The antibody-based product must be processed to high levels of purity, and specific contaminants such as DNA and endotoxin must be reduced to extremely low levels . Appropriate labeling or drug conjugation chemistries must also be developed . The product must be formulated so that it has performance characteristics that are stable over a reasonable period of time . Adequate test procedures must be developed to assure product purity, activity, stability, and safety on a lot-to-lot-basis . Compliance with federal regulations, guidelines, and procedures must be guaranteed . In the coming decade, it is likely that the two arms of biotechnology, hybridoma technology and recombinant DNA technology, will be used together to generate unique protein molecules . These new reagents will face the same practical considerations summarized in this review. Appl Environ Microbiol, 1989 Apr, 55(4), 866 - 70 Kinetics of p-cresol degradation by an immobilized Pseudomonas sp; O'Reilly KT et al.; A p-cresol (PCR)-degrading Pseudomonas sp . was isolated from creosote-contaminated soil and shown to degrade PCR by conversion to protocatechuate via p-hydroxybenzaldehyde (PBA) and p-hydroxybenzoate (PHB) . Cells of the Pseudomonas sp . were immobilized in calcium alginate beads and in polyurethane foam . The relationship between the PCR concentration and the PCR transformation rate was investigated in batch and continuous culture bioreactors . The biodegradation kinetics of PBA and PHB also were investigated . In batch culture reactors, the maximum PCR degradation rate (Vmax) for the alginate-immobilized Pseudomonas sp . cells was 1.5 mg of PCR g of bead-1 h-1 while the saturation constant (Ks) was 0.22 mM . For PHB degradation, the Vmax was 0.62 mg of PHB g of bead-1 h-1 while the Ks was 0.31 mM . For polyurethane-immobilized Pseudomonas sp . cells, the Vmax of PCR degradation was 0.80 mg of PCR g of foam-1 h-1 while the Ks was 0.28 mM . For PHB degradation, the Vmax was 0.21 mg of PHB g of foam-1 h-1 and the Ks was 0.22 mM . In a continuous column alginate bead reactor, the Vmax for PCR transformation was 2.6 mg g of bead-1 h-1 while the Ks was 0.20 mM . The Vmax and Ks for PBA transformation in the presence of PCR were 0.93 mg g of bead-1 h-1 and 0.063 mM, respectively . When PHB alone was added to a reactor, the Vmax was 1.48 mg g of bead-1 h-1 and the Ks was 0.32 mM.(ABSTRACT TRUNCATED AT 250 WORDS) Gan To Kagaku Ryoho, 1989 Apr, 16(4 Pt 2-3), 1888 - 92 {Mass culture of LAK cells by a hollow-fiber bioreactor system}; Tanji Y et al.; We attempted to culture LAK cells by the use of the hollow-fiber bioreactor system, "Acusyst-P" . The number of LAK cells increased by 30-40 times . The majority of LAK cells cultured by this hollow fiber system originated in T cell . LAK cells cultured by hollow-fiber system were different from LAK cells statically cultured in their cytotoxicity and change of phenotype . We obtained LAK cells more efficiently and safely which have higher viability and cytotoxicity by the use of hollow-fiber bioreactor system than by static culture. Biotechniques, 1989 Apr, 7(4), 368 - 73 Effect of agitation rate and impeller design on oxygen transfer coefficients in small bioreactors using surface aeration; Sybert EM et al.; The effects of agitation rate and impeller type on the combined oxygen mass-transfer coefficient (kL a) in four different benchtop bioreactors have been examined . Surface oxygenation of a cell culture medium supplemented with fetal bovine serum and distilled deionized water has been studied by passing air through the bioreactor headspace at approximately one headspace volume per minute . A new ribbon-type impeller design using strips of Teflon has been shown to be superior to conventional impeller designs for oxygen transfer. Biotechniques, 1989 Feb, 7(2), 192 - 9 Monoclonal antibody production in hollow fiber bioreactors using serum-free medium; Heifetz AH et al.; Murine hybridoma cells that produce monoclonal antibody directed against human fibronectin have been cultured in VITAFIBER II and VITAFIBER V hollow fiber bioreactors using defined, serum-free WRC 935 medium . During a two-week growth period, following inoculation of the bioreactors, the cells proliferated to an extent where the bioreactor was filled with cultured cells . Using a 5 sq . ft . VITAFIBER V bioreactor, over 15 grams of antibody were produced during the 40 days of the experiment . This antibody was greater than 95% IgG . During the production period, this packed mass of cells produced 579 +/- 15 mg IgG per day . Because the medium is formulated for air equilibration and high cell densities, WRC 935 medium is especially useful for production of gram quantities of monoclonal antibodies using continuous feed hollow fiber bioreactor cell culture systems. J Parenter Sci Technol, 1989 Jan-Feb, 43(1), 15 - 23 The recovery of highly purified biopharmaceuticals from perfusion cell culture bioreactors; Prior CP et al.; The impact of continuous perfusion cell culture technology on production of one and two chain human rtPA, as well as monoclonal IgG and IgM, will be reviewed . Perfusion as compared to batch systems improve the quality of the product in the conditioned media in terms of biological activity and structural integrity . This significantly increases downstream recovery and daily production output of final purified material . These findings are a consequence of the ability of perfusion technology to 1) maintain cells intact at high cell density; 2) effectively reduce serum content to approximate serum free conditions; and 3) minimize residency time of labile product within the 37 degrees C environment of the bioreactor. Boll Soc Ital Biol Sper, 1989 Jan, 65(1), 19 - 22 {Several properties of human red cells subjected to hypotonic dialysis and resealing to use them as vehicles for bioreactors}; Rossi L et al.; The morphological and metabolic properties of red blood cells submitted to the procedure of loading by hypotonic hemolysis and isotonic resealing were compared with the controls . No appreciable differences could be detected concerning glycolytic ability, the amount of glucose metabolized in the hexose monophosphate pathway and the concentrations of glycolytic intermediates of ATP and of 2,3-DPG . Instead the concentration of reduced glutathione and the MCV were slightly reduced . These manipulated erythrocytes can be used as potential bioreactors or as carriers of exogenous substances. Plant Foods Hum Nutr, 1989, 39(1), 59 - 65 Digestibilities of the protein in various foods as determined in vitro by an immobilized digestive enzyme assay (IDEA); Thresher WC et al.; The digestibility of the protein in various foods or food components was analyzed using an immobilized digestive enzyme assay (IDEA) system . The assay consists of two bioreactors, one containing pepsin and the other containing trypsin, chymotrypsin and intestinal mucosa peptidases . The fraction of the peptide bonds hydrolyzed during an extent of hydrolysis assay was correlated with independent in vivo determinations of the digestibilities . A correlation coefficient of 0.80 was obtained . The derived linear regression equation can be used to predict digestibility . The method is sensitive to structural modification of protein, as for example, those caused by effects of heat treatment. Adv Biochem Eng Biotechnol, 1989, 39, 73 - 95 Microbeads and anchorage-dependent eukaryotic cells: the beginning of a new era in biotechnology; Miller AO et al.; Modern methods for the mass cultivation of anchorage-dependent mammalian cells started with the advent of microcarrier technology . Largely for reasons pertaining to their mode of preparation and ease of cultivation, 150-230 microns microbeads have been overwhelmingly adopted and the technology around them developed . To meet high biomass, macroporous microbeads have been developed . Also, the chemistry of the microsupport has been adapted in order to afford better protection of fragile cells to mechanical wear while simultaneously reorienting their differentiation towards the sought aims (production of cytokines, enzymes etc . ...) . Future progress depends upon solutions being brought to problems inherent to this new technology (maintenance of steady state conditions of growth etc . ...) as well as to requirements arising from animal cell culture in general (biosensors, bioreactor's design etc . ...) . Besides such technical implementations, biology at large is also expected to benefit from the advent of microcarriers in fields as diverse as the preparation of metaphasic chromosomes in bulk, toxicity testing, organ reconstitution following cell transplantation etc. Adv Biochem Eng Biotechnol, 1989, 40, 137 - 69 Effect of total and partial pressure (oxygen and carbon dioxide) on aerobic microbial processes; Onken U et al.; In industrial bioreactors, levels and gradients of total and partial pressures are considerably higher than on the laboratory scale . In the relevant range (in general up to 2 or 3 bar, maximum approx . 10 bar), effects of total pressure on aerobic cultures are negligibly small . CO2 partial pressures of more than approx . 100 mbar may have inhibitory effects on aerobic cultures . Growth of aerobic cultures can be enhanced by O2 partial pressures higher than 210 mbar (corresponding to air at 1 bar), if oxygen transfer is limited . In many cases, however, increased O2 partial pressure (higher than approx . 1 bar) is toxic to aerobic cultures and inhibits microbial growth and product formation . Stepwise and cyclic variations of O2 partial pressure may have positive or negative effects, depending on strain of microorganism, culturing conditions, and range of dissolved oxygen concentration . Knowledge of these effects is required in process development and bioreactor scale-up. Adv Biochem Eng Biotechnol, 1989, 40, 1 - 18 Recent developments in enzyme and microbial biotechnology--strategies in bioprocess design; Hardman N; Microorganisms have been used traditionally by industry as sources of natural products, or as sources of enzymes capable of mediating specific chemical transformations . This situation has changed radically in recent years, a time during which we have seen a dramatic increase in the number and range of potential biotechnological applications of enzymes and their genetically-engineered variants . An increasing number of enzymes, receptors and other proteins have now been structurally characterized, and their genes isolated as a basis for producing recombinant proteins for genetic analysis of their structure and function . These innovations have necessitated development of associated technologies for large-scale production of proteins in bioreactors, appropriate strategies for quality control, and new analytical tools for structural characterization of recombinant gene products . Some recombinant proteins are already in an advanced stage of development for use either as new-generation therapeutics, as target molecules for "intelligent" drug screening, or as biological components of biosensors . As the predictive power of protein model building improves, the diversity of applications of such technology will increase further as it becomes feasible to generate totally synthetic proteins with specifically-tailored properties. Adv Biochem Eng Biotechnol, 1989, 39, 29 - 71 Bioreactor for mammalian cell culture; Prokop A et al.; Purpose of this article is to review the current status of bioreactor design for mammalian cell culture . Morphological and biochemical features of two major mammalian cell groups, anchorage-dependent and independent cells are proposed as a basis for different behavior at their cultivation . Different bioreactor configurations are systematically discussed through enumerating elementary physical phenomena and through stressing their physiological significance . Special considerations are given to those areas which are inherent to mammalian cell bioreactor. Dev Biol Stand, 1989, 70, 49 - 56 Manufacture of pharmaceutical proteins from hybridomas and other cell substrates; Tolbert WR et al.; Murine monoclonal antibodies are now routinely produced from highly expressing hybridoma cell lines for human clinical applications . Epstein Barr Virus transformed human lymphocytes are used to produce human monoclonal antibodies but these cells have generally exhibited low expression and poor stability in culture when compared with typical murine hybridomas . Alternative cells are therefore finding wider usage . Backfusions and tribrids are being used to increase and/or prolong the expression of monoclonal antibodies . In addition, genetically engineered cells producing antibodies with human constant and murine variable regions may reduce antigenicity of the chimeric protein used for injection . Pharmaceutical acceptability of the final product is also strongly dependent on culture and purification methods that are used in the manufacturing process . Large scale perfusion technology has allowed high density, efficient monoclonal production in the absence of antibiotics in low serum or serum free media . These methods reduce the cell protein/DNA challenge to the purification process by dead and dying cells and also prevent product degradation by reducing product residence time within the bioreactor . Gentle purification procedures that avoid extremes of pH and salt concentration can preserve structural integrity and biological activity of the protein and can provide high yields and purity in excess of 99% . Such purification procedures alone or in combination with specific viral inactivation steps can be validated to have the capability overall to reduce virus concentration by a factor of 10(8) to 10(12) . The combination of carefully developed cell substrates, with advanced perfusion culture and purification technology can consistently produce acceptable protein-based pharmaceutical products in compliance with cGMP's. Chin J Biotechnol, 1989, 5(4), 253 - 61 Operation of fluidized-bed bioreactor containing immobilized yeast cells and the diacetyl levels of green beer; Wang YJ et al.; A fluidized-bed bioreactor containing yeast cells immobilized in calcium alginate gel was operated by means of a circulating wort system . The optimum volume fraction of gel beads was found to be 0.40 (phi, v/v) for fermentation . The effects of the flow rates of the wort on the period of the primary fermentation and the diacetyl levels in green beer were studied under the conditions of the volume fraction of gel beads at phi = 0.40, the fermentation temperature at 10 degrees C, and the ratio of circulation at n = 5 . The experimental results indicated that the period of the primary fermentation was shortened as the flow rate of wort increased, whereas the concentration of diacetyl increased with the increasing flow rate of the wort . The period of the primary fermentation and the concentration of the diacetyl were found to be 14 h and 0.5 ppm respectively, when the residence time tau t in the reactor was 2.8 h. Chin J Biotechnol, 1989, 5(2), 123 - 31 Studies on circulation rate and flow model for external loop bioreactor; Liu K et al.; We performed experiments in an external loop bioreactor 250 mm in diameter and 4500 mm in height . The variation in circulation rate Um was studied over a wide range of surface gas velocities (UG = 0-24.9 cm/s), and a bioreactor flow model was obtained . We developed a new method (i.e., an electrical conductivity tracking system) to measure circulation rate and solve the problem of measuring general circulation resistance . A theoretical formula for Um was derived for use in scaling up the bioreactor: {formula: see text} Antibiot Khimioter, 1988 Nov, 33(11), 817 - 20 {Biodegradation of pollutants in the aerial discharges from antibiotic biosynthesis}; Markov IA et al.; Possible biodegradation of air pollution from antibiotic biosynthesis in the form of water condensates was studied in a 1000 ml laboratory bioreactor with using active sludge . The biodegradation of such a pollution was shown possible . The process kinetics was described by the Michaelis-Menten equation . The values of the equation constants were calculated. Biotechniques, 1988 Sep, 6(8), 762 - 7 Large-scale production of murine monoclonal antibodies using hollow fiber bioreactors; Evans TL et al.; We have produced large quantities of murine monoclonal antibodies for in vivo human clinical trials using hollow fiber bioreactors (HFBRs) . Thirty-three different hybridoma cell lines have been evaluated in various HFBR systems . Monoclonal antibody (Ab) productivity is highly dependent on the intrinsic secretory rate of each cell line . Other factors that affect Ab production include capillary membrane molecular weight cutoff, and HFBR design . Studies comparing HFBRs to static and suspension culture systems revealed similar Ab productivity . An advantage of the HFBR is that the Ab is concentrated in the extracapillary space, simplifying downstream processing. J Gen Microbiol, 1988 Aug, 134 ( Pt 8), 2241 - 8 The effect of dissolved oxygen concentration on the growth physiology of Saccharomyces cerevisiae whi2 mutants; Rahman DR et al.; Isogenic whi2 and WHI2+ strains of Saccharomyces cerevisiae were grown in a 2-litre bioreactor as batch cultures on a medium containing yeast extract and peptone with either glucose or ethanol as carbon and energy source . The concentration of dissolved oxygen within the medium was varied over the range of 0 to 100% saturation . Expression of the whi2 phenotype only occurred above 40% oxygen saturation with either glucose or ethanol as carbon and energy source . Under these conditions the whi2 cells could be distinguished from WHI2+ cells in that they were phase dark, highly budded and very small during the stationary growth phase, and reached final cell densities four to six times higher than WHI2+ cells . The results clearly show that the WHI2 gene of S . cerevisiae plays an important role in cell proliferation and that the availability of oxygen, or some product of oxidative metabolism, is involved in regulating the phenotypic expression of mutations within this gene. Zhonghua Min Guo Wei Sheng Wu Ji Mian Yi Xue Za Zhi, 1988 Aug, 21(3), 125 - 40 {Continuous production of anti-hepatitis B surface antigen monoclonal antibody in hollow fiber perfusion bioreactor}; Meng MH et al.; Hybridoma cell line H440Ac was cultivated continuously in hollow fiber perfusion bioreactor for fifty days to produce anti-hepatitis B surface antigen (anti-HBsAg) monoclonal antibody . A total of 90 mg anti-HBsAg antibody was produced in the hollow fiber bioreactor with 1000 cm2 membrane surface area . The collected production medium has an average antibody concentration of 0.45 mg/ml with a high concentration of 2.3 mg/ml . This compares with 0.016 and 1.1 mg/ml antibody concentration as collected from spinner flask and mouse ascites . The purity of the produced antibody is 0.085, 0.0028 and 0.026 mg antibody per mg of total harvested protein in the culture media produced from the hollow fiber bioreactor, spinner flasks and mouse ascites, respectively. ASAIO Trans, 1988 Jul-Sep, 34(3), 732 - 8 A novel bioreactor based on suspended particles of agarose-immobilized species; Freed LE et al.; Bioreactors often contain porous particles of agarose because these provide an enormous surface area (50 m2/cc gel) onto which enzymes or antibodies can be immobilized . Although many investigators claim that contact with agarose induces significant blood damage, we find that the biocompatibility of immobilized agarose is significantly improved when a novel system is used to fluidize the particles within the bioreactor vessel . We have built a prototype device that is oscillated vigorously about the axis of fluid flow . This action produces secondary flow patterns within the vessel that suspend the particles . In our model system, the bioreactor contains agarose immobilized heparinase . The system is biocompatible for 2 hours in vitro (in human blood at 37 degrees C) as follows: 1) hematocrit, white cell, and platelet counts do not change, 2) levels of plasma hemoglobin increase to 15-34 mg/dl, and 3) levels of complement component C3a increase to 0.64-1.4 micrograms/cc . We hope these studies lead to the development of a heparin removal system that can improve the safety of a variety of extracorporeal procedures . In addition, the techniques and approach used are sufficiently general to permit their extension to any immobilized species bioreactor for blood detoxification. Anal Biochem, 1988 Jul, 172(1), 89 - 95 Immobilization of linamarase and its use in the determination of bound cyanide in cassava using flow injection analysis; Narinesingh D et al.; Extracts from the tubers (cortex and parenchyma) and leaves of Manihot esculenta Crantz (cassava) were analyzed for their releasable cyanide content using flow injection analysis incorporating an immobilized linamarase bioreactor . Linamarase was immobilized under very mild conditions to an activated 2-fluoro-N-methylpyridinium Fractogel support . The released cyanide, which was monitored spectrophotometrically at 525 nm using an alkaline picrate reagent, was found to be highest in the cortex and lowest in the parenchyma. Proc Natl Acad Sci U S A, 1988 May, 85(9), 3145 - 9 Conversion of encapsulated 5-fluoro-2'-deoxyuridine 5'-monophosphate to the antineoplastic drug 5-fluoro-2'-deoxyuridine in human erythrocytes; De Flora A et al.; The fluoropyrimidine deoxyribonucleotide 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP) was encapsulated in human erythrocytes by a procedure based on hypotonic hemolysis and isotonic resealing . Encapsulated FdUMP (up to 9 mumol/ml of packed erythrocytes) did not affect erythrocyte metabolism or morphology . Hemolysates were found to catalyze efficient dephosphorylation of FdUMP to yield nearly stoichiometric amounts of the corresponding deoxyribonucleoside 5-fluoro-2'-deoxyuridine (FdUrd), an antineoplastic drug showing selective cytotoxicity toward liver metastases from colorectal carcinomas . The dephosphorylation reaction had an apparent Km of 7.7 +/- 1.2 mM FdUMP at pH 7.4 and was remarkably slower at pH 8.2 . ATP, GTP, and UTP inhibited both the disappearance of FdUMP and the formation of FdUrd in hemolysates . The enzyme responsible for the FdUMP-to-FdUrd conversion was identified with the deoxyribonucleotide-specific isozyme of erythrocyte pyrimidine 5'-nucleotidase (EC 3.1.3.5) . Intracellular formation and subsequent release of FdUrd were observed in intact erythrocytes loaded with FdUMP . Inhibition of FdUrd release from these erythrocytes was obtained by raising the pH intracellularly and, alternatively, by coencapsulation of ATP . Autologous FdUMP-loaded erythrocytes might be used as endogenous bioreactors designed for time-programmed and liver-targeted delivery of FdUrd. J Biolumin Chemilumin, 1988 Apr-Jun, 2(2), 63 - 7 A chemiluminometric method for the determination of urea in serum using a three-enzyme bioreactor; Tabata M et al.; A flow injection chemiluminometric assay for urea has been developed based on a minicolumn bioreactor packed with immobilized enzyme-bearing glass beads . The reactor contains immobilized urease, L-glutamate dehydrogenase and L-glutamate oxidase, aligned in this order (upstream to the downstream) . When the sample is introduced into the bioreactor, urea is first hydrolysed by urease to produce ammonia, which is then converted into L-glutamate by L-glutamate dehydrogenase . L-Glutamate is finally oxidized by L-glutamate oxidase to produce hydrogen peroxide, which is quantified by measuring chemiluminescence emitted upon admixing with luminol and potassium ferricyanide . One assay cycle is completed within 1 minute . The method is sensitive (detection limit 0.5 nmol) and is linear in the range 0-30 mmol/l . It can be readily applied to the determination of urea in human serum, and requires no blank corrections for ammonia and/or L-glutamate present in serum samples. Gen Physiol Biophys, 1988 Feb, 7(1), 59 - 71 May active solute flux control the cell volume in the steady state? Wierzchaczewski M. The dynamics of a bioreactor with a variable volume and an active solute flux based on the thermodynamics of irreversible processes and stability analysis was studied . The active solute flux may control both the bioreactor volume and the hydrostatic pressure as well as the concentration of the solute inside the cell in the steady state . The range of the active solute flux is limited by amplitudes (j1(0), J2(0} of the active transport depending on the membrane transport parameters . The dynamic system is stable for j0 greater than jth0. Arzneimittelforschung, 1988 Feb, 38(2), 320 - 5 Fermentation with immobilized cell cultures; Werner RG et al.; For the production of monoclonal antibodies and complex recombinant human proteins or glycoproteins a number of immobilized cell culture systems have been developed . The advantages of such cell culture systems are that cells can be kept in small volumes of cell culture fluid and media can be changed continuously if necessary for induction of product synthesis or removal and harvest of metabolic products . Whereas the hollow fiber and the opticell culture systems can be limited in scaling up the microcarrier system, the fluidized bed bioreactor and the solid bed bioreactor are suitable for scaling up . In contrast to the other systems, the solid bed bioreactor requires no special manipulation for anchoring the cells to the wire springs . In situ cleaning is possible and the beads are reusable . With this cell culture fermentation system, production processes for interferon beta, monoclonal antibodies for interferon alfa and recombinant human tissue plasminogen activator were developed. Int J Rad Appl Instrum B, 1988, 15(3), 261 - 70 Anti-colon/ovarian tumor antigen: localization of colon cancer xenografts in athymic rats; Zamora PO et al.; Tumor localization studies in athymic rats bearing human colon tumors were performed using the radioiodinated monoclonal antibody SP-21 and its F(ab')2 . Antibody preparations isolated from ascitic fluid and antibody from bioreactor effluent were used in these studies with similar radioimmunolocalization results . The intact antibody had an optimal localization time of 4-8 days after injection, while the F(ab')2 fragments had an optimal localization time of 3-4 days . Whole-body autoradiography, whole-body immunohistochemistry, and scintigraphy confirmed that the intact antibody and the antibody fragments localized preferentially in the tumor . The antibody distribution within the tumor was uniform, and not confined to the periphery, nor to focal areas within the tumor . Dose-response studies were performed with the intact antibody over a range of 10-100 micrograms/kg of total body weight with no clear-cut relationships observed . Comparisons of different radio-iodination methods indicated that the chloramine-T-based methods resulted in preparations with higher tumor uptake. Biotechniques, 1988 Jan, 6(1), 62 - 7 A new serum-free medium for monoclonal antibody production; Wolfe RA et al.; A new serum-free, defined-protein, medium for the growth of murine hybridoma cells and the production of monoclonal antibodies has been developed . Designated WRC 935 medium, this formulation supports the growth of hybridoma cells in higher numbers, and promotes better cell viabilities and increased monoclonal antibody levels compared to growth in DMEM supplemented with 10% fetal bovine serum or in a DMEM/F-12 serum-free mixture . In suspension cultures, WRC 935 medium typically promoted cell growth to densities over two million cells per milliliter . This medium also promoted the rapid growth of cells following their transfer from liquid nitrogen storage . WRC 935 medium is especially useful for high density cell culture production methods using hollow-fiber bioreactors . Hollow-fiber bioreactors using this medium produced antibody at an average rate of 11 mg/day, and the antibody concentration ranged from 10 to 40 mg/ml. Klin Wochenschr, 1988, 66 Suppl 12, 24 - 32 {Biotechnical production of drugs with special reference to tissue-type plasminogen activator}; Werner RG; On the basis of recombinant DNA-technology, new biotechnology is able to provide active human proteins which can be applied for replacement therapy to patients, whose symptoms of illness are based on the lack of these proteins . One of the most thoroughly investigated compounds in this aspect is tissue plasminogen activator (t-PA) which under pathophysiological conditions is not available in sufficient quantities; as a result formed thrombi cannot be dissolved sufficiently by endogenous means . Consequently, t-PA is produced biotechnically and applied exogenously to the patients . Such proteins only can be produced by biotechnology for therapeutic purposes because a chemical synthesis is not economical and isolation from human tissues or body fluids is not possible due to low concentrations, safety aspects or ethical reasons . Resulting from the knowledge of molecular biology, the genetic information for the synthesis of a distinct protein can be transferred into a suitable host cell for efficient production, by methods of recombinant DNA-technology . Thereby the choice of the producing organism is determined by the complexity of the protein . After the growth phase of the producing cells the biological active protein is obtained with a purity greater than 99.9% from the production bioreactor by protein chemical methods . Quality assurance is guaranteed by manifold protein chemical, electrophoretic, immunologic, enzymatic and biological methods . A high stability of such biologically active proteins is achieved by lyophilization after achieving a high degree of purity and a suitable formulation.(ABSTRACT TRUNCATED AT 250 WORDS) Mol Biother, 1988, 1(2), 61 - 73 An integration of cultivation and purification in membrane bioreactors: production of monoclonal antibodies and lymphokines by microencapsulated hybridomas; Prokop A; Engineering and physiologic aspects of growth and production processes associated with encapsulated cells, mostly of anchorage-independent type, are reviewed . They include membrane diffusion characterization, mechanical properties of microcapsules, process limiting phenomena, physiological state of cells, process modeling and product purity and concentration . Finally, application areas are spelled out with an outlook discussion. Prep Biochem, 1988, 18(4), 483 - 9 Immobilization of Aspergillus ficuum phytase: product characterization of the bioreactor; Ullah AH et al.; Aspergillus ficuum phytase was covalently immobilized on Fractogel TSK HW-75 containing 2-oxy-l-alkylpyridinium salts . A packed-bed bioreactor was constructed with the immobilized phytase . An HPLC ion-exchange method was used to analyze the enzymatic products of the bioreactor . Immobilized fungal phytase was able to hydrolyze myo-inositol Hexa-, penta-, tetra-, tri-, and diphosphates . When the substrate solution was recirculated for 5 hr in the bioreactor about 50% inorganic orthophosphate was released and myo-inositol-diphosphate and mono-phosphate were the only remaining products. Biotechnol Appl Biochem, 1987 Aug, 9(4), 303 - 9 Use of a bioreactor consisting of sequentially aligned L-glutamate dehydrogenase and L-glutamate oxidase for the determination of ammonia by chemiluminescence; Murachi T et al.; A chemiluminometric method for the automated flow injection analysis of ammonia is described . The essence of the invention is the use of a bioreactor consisting of both immobilized L-glutamate dehydrogenase (GLDH) and L-glutamate oxidase (GLXD), which are sequentially aligned in this order in a minicolumn measuring 2.0 X 20 mm . The unidirectional constant flow of liquid through the column reactor minimizes the reversed diffusion of the solutes so that the following sequence of reactions is ensured . Thus, ammonia to be determined is first transformed by GLDH into L-glutamate, which then produces hydrogen peroxide by GLXD . Hydrogen peroxide in the effluent from the column is then determined by its chemiluminescence upon admixing with luminol and potassium ferricyanide . The present method gives linearity of the standard curve for ammonia up to 1.0 mM . It is at least 100 times more sensitive than the conventional method for ammonia assay using ultraviolet absorption measurement. Appl Biochem Biotechnol, 1987 Jun, 15(1), 25 - 34 Enzyme-catalyzed, gas-phase reactions; Barzana E et al.; Dehydrated preparations of alcohol oxidase adsorbed on DEAE-cellulose vigorously catalyze a gas-phase oxidation of ethanol vapors with molecular oxygen . The gas-phase reaction is strongly dependent on the water activity of the system . The enzymatic activity is severely inhibited by the product hydrogen peroxide . This inhibition can be alleviated, however, by an addition of catalase or peroxidase to the dry preparation . Such dehydrated, bienzymic catalysts afford a complete and selective conversion of the substrate to acetaldehyde . Dry alcohol oxidase is much more thermostable than in aqueous solution . The results of this work suggest that dehydrated enzymes have potential applications in the analysis of gaseous compounds and in the development of novel gas-solid bioreactors. Dev Biol Stand, 1987, 66, 489 - 93 Production of human beta-interferon in mouse L-cells; Schulz R et al.; Mouse L-cells, producing glycosilated human beta-interferon constitutively, were cultivated on microcarriers in bioreactors, equipped with a bubble-free aeration system up to 22 1 scale . Suitable aeration membrane surfaces and medium exchange rates permitted cultivation up to 8 X 10(6) cells/ml with a specific beta-interferon productivity of 2 X 10(4) U/10(6) cells/day . A correlation was found between the number of cell layers on the microcarriers and the specific human beta-interferon productivity. Dev Biol Stand, 1987, 66, 241 - 53 On the evaluation of gas-liquid interfacial effects on hybridoma viability in bubble column bioreactors; Handa A et al.; Sparger aeration, with or without mechanical agitation is the simplest method of providing an oxygen supply . Although earlier workers have demonstrated the sensitivity of mammalian cells to air bubbles, recent successful applications of the airlift principle to hybridoma culture indicate that under some conditions, the cells can withstand these effects . Therefore, this work has as its objective the elucidation of the relationship between gas-liquid interfaces and the survival of mammalian cells . Simple, 0.5 litre bubble columns with sintered discs are used batch-wise to study the effects of sparging on hybridomas and other mammalian cells in suspension culture . The effects of bubble diameters, superficial gas velocities and the non-ionic surfactant, Pluriol PE 6800, are investigated in cultures grown in RPM1 1640 with 5% foetal calf serum and 6 ppm silicone antifoam . From these studies it has become apparent that cell viability and survival in the presence of bubbles depend on: Cell type--Some cell lines are shown to be particularly sensitive to the presence of bubbles, although no gross morphological differences are detected by electron microscopy . Bubble sizes--At a superficial gas velocity of 0.42 X 10(-4)m/s (5 cc/min gas flow rate), small bubbles are shown to be more detrimental to the cells than the larger ones . Bubble frequency/superficial gas velocities--Increasing superficial gas velocities (0.42 X 10(-4) to 8.5 X 10(-4) m/s) result in decreasing cell viability . Where the presence of bubbles is detrimental to cell growth, the addition of the non-ionic surfactant, Pluriol PE 6800, has a concentration dependent protective effect . Surface tension, viscosity and bubble diameter data for typical medium will be presented . A novel application of microscopy to which video film systems can be applied for direct visualisation of the cells in the bubble column has been developed . From these studies, it is indicative that both the geometry of the system and the cell type are important in mammalian cell culture scale-up strategy. Dev Biol Stand, 1987, 66, 211 - 20 A hollow fibre dialysis system for the in vitro production of monoclonal antibodies replacing in vivo production in mice; Schonherr OT et al.; Haemodialysis units have been used as bioreactors for the in vitro production of monoclonal antibodies . Mouse hybridomas were grown in the extra-capillary compartment of dialysis modules with a constant supply of protein-free medium through the hollow fibres . It was found that addition of serum to the media had no stimulatory effect on the production of monoclonal antibodies . For the determination of monoclonal antibodies a sol particle immunoassay (SPIA) has been used . Monoclonal antibodies were harvested from the extra-capillary compartment at two-week intervals over periods of several weeks at concentrations comparable to the harvests of ascitic fluids from mice . The production capacity of one haemodialysis unit is equivalent to that of at least 50 mice . This in vitro system enables a yearly production of 50 grams per unit of monoclonal antibodies of high purity and devoid of contaminants from mouse origin or serum . It has been shown that this system can be successfully used to produce a constant supply of monoclonal antibodies for a variety of applications, e.g . reagents for diagnostic tests and materials for immuno-chromatographic purification . As a consequence this in vitro production of monoclonal antibodies has replaced the many thousands of mice required for in vivo production. Folia Microbiol (Praha), 1987, 32(1), 65 - 81 New trends in microbial technology; Rehacek Z et al.; Microbial technology includes not only the production of materials in bioreactors, or the production of new catalysts by genetic engineering but extends to aspects of both human and animal health care, waste and pollution management, enhanced oil recovery, mineral leaching, advanced plant breeding, diagnostics and analytical equipment, biosensors, bioelectronics and renewable energy system based on biomass feedstocks . National strategies of industrialized countries are being developed which identify microbial technology as a substantial factor in the attainment of industrial and economic goals . Although extremely promising microbial technology is not a quick fix and its application will only arise as a result of systematic programme of research and development . Such programme requires a broad base of disciplinary underpinning in molecular biology, genetics and bioengineering . The development of expertise of this kind in the tertiary educational institutions is the essential starting point . It should be developed by appropriate programmes and networking systems. Zentralbl Mikrobiol, 1987, 142(8), 595 - 604 {Special conditions for the cultivation of genetically engineered microorganisms}; Krug M et al.; Using recombinant strains recently the cultivation of microorganisms for biotechnological purposes has reached a qualitative new level . With respect to the optimization of such cultivation processes appropriate variations of genetical, physiological and biochemical parameters will be necessary . This review summarizes trends of construction of vectors and problems of correlations between hosts and vectors with regard to their application in discontinuous and continuous bioreactor-procedures. Appl Biochem Biotechnol, 1986 Dec, 13(3), 181 - 7 Oxygen limitation on L-serine production in a hollow-fiber bioreactor; Klier J et al.; Pseudomonas AM1 utilizes glycine and methanol to produce L-serine aerobically . The consumption of methanol in this bioconversion is stoichiometrically in excess of L-serine production . Consequently, the oxygen requirement associated with L-serine production is higher than expected for the conversion from glycine . One method of L-serine production investigated was a technique utilizing a hollow-fiber ultrafiltration cartridge as a bioreactor . Oxygen diffusion limitations appear to impede the consumption of methanol and, consequently, the production of L-serine in such a reactor . Methanol consumption data agree with predictions based on a hollow-fiber diffusion model. Ital J Biochem, 1986 Sep-Oct, 35(5), 361 - 7 Construction of glucose oxidase-loaded human erythrocytes: a model of oxidative cytotoxicity; De Flora A et al.; Human red blood cells were loaded with Glucose oxidase from Aspergillus niger by a standardized procedure of encapsulation involving transient hypotonic hemolysis followed by isotonic resealing . The amount of loaded enzyme activity, as evaluated by O2 consumption at 5 mM glucose, ranged from 40 to 75 mumoles O2/hr/ml of packed red cells at 37 degrees C . The red cells loaded with Glucose oxidase were found to behave as efficient glucose-consuming bioreactors . Moreover, at 5 mM glucose, no clear mechanism of H2O2-induced damage was apparent, with the exception of a significantly increased formation of methemoglobin (10% approximately) and of a several-fold stimulated intracellular rate of hexose monophosphate shunt activity, indicating glutathione peroxidase-mediated draining of reduced glutathione for removal of bursts of H2O2 . The Glucose oxidase-loaded red cells represent a convenient model system for cytotoxicity studies aiming at clarifying the effects of intracellularly formed H2O2. Int J Artif Organs, 1986 Sep, 9(5), 331 - 4 Enzyme-based hemoperfusion and blood treatment; Lotan N et al.; Enzyme-based artificial organs are being developed as metabolic assist devices . These are required when normal metabolism is impaired, or when the body is overloaded by undesired metabolites or toxins . The implementations of this approach for treating a genetic disease, and for metabolic support in liver failure are envisaged . The kinetic aspects and mass transfer characteristics of bioreactors for these systems are considered in detail. Ann N Y Acad Sci, 1986, 469, 53 - 62 Using fault analysis methods to improve bioreactor safety; Jefferis RP 3rd et al.; A simplified fault analysis algorithm has been described and applied to the analysis of containment loss in a model bioreactor system . Using approximate data for component failure rates, the relative merits of three proposed operating regimes were evaluated by means of a computer program that implements the algorithm described . With the data given, operator error is shown to be the dominant cause of possible failure in the proposed system . In view of these results, the simplified algorithm appears useful for the comparative evaluation of various design proposals in simple systems. J Theor Biol, 1985 Nov 21, 117(2), 209 - 30 The organism as bioreactor . Interpretation of the reduction law of metabolism in terms of heterogeneous catalysis and fractal structure; Sernetz M et al.; Organisms and bioreactors are open, dissipative systems in steady state . They are functionally equivalent with respect to turnover and kinetics, and structurally analogous with respect to fractal organization and self-similar scaling . As heterogeneous catalytic systems both are governed by interaction of mass transport and reaction . The structural equivalent to turbulence in the reactor, yielding high efficiency, is the fractal folding and branching of the transport systems of the organism . Dimensionally and in terms of fractals, organisms and reactors are therefore area-volume hybrids . The physiological consequence of this is the reduction law of metabolism . Introducing limits into allometric functions describing scale-up of similar organisms yields probability density distributions of their realization. J Dairy Sci, 1985 Oct, 68(10), 2782 - 90 Digestibility of modified milk proteins: nutritional implications; Swaisgood HE et al.; Chemical changes in the structure of several milk proteins were quantitated and the effects on digestibility evaluated using a number of in vitro techniques developed in our laboratory . An assay for digestibility was developed and standardized incorporating immobilized gastric, pancreatic, and intestinal mucosal proteinases and peptidases and thereby simulating in vivo digestion . The method displayed a direct relationship to digestibilities determined in human feeding studies . Various degrees of racemization were induced in a number of proteins and quantitated with the aid of a bioreactor containing coimmobilized D-amino acid oxidase and catalase . Digestibility values were directly related to the degree of racemization and to the amount of lysinoalanine . In a separate study of these proteins, various degrees of Maillard reaction were induced, and the available lysine was quantitated using the fluorometric o-phthalaldehyde method . Digestibility values determined for these modified proteins were also directly related to the amount of available lysine . A bioreactor containing various immobilized proteinases and peptidases catalyzed complete hydrolysis of a number of proteins including beta-lactoglobulin . Because this method does not degrade residues such as tryptophan and methionine nor hydrolyze aldosyl lysine to give unmodified lysine, analysis of these hydrolysates yields more nutritionally meaningful chemical scores . In summary, these techniques appear to be useful for quantitating and monitoring changes in the structures of proteins resulting from processing and storage, which affect their nutritional quality. Z Naturforsch {C}, 1985 Jan-Feb, 40(1-2), 61 - 7 Production of four interfacial active rhamnolipids from n-alkanes or glycerol by resting cells of Pseudomonas species DSM 2874; Syldatk C et al.; In a simple phosphate buffer or a sodium chloride solution resting cells of Pseudomonas spec . DSM 2874 produced up to 15 g/l of different rhamnolipids . The rhamnolipid composition of the organic crude extract depended on the temperature during the cultivation and on the C-source . The optimal sodium chloride concentration for rhamnolipid formation was about 100 mM/l and the optimal phosphate buffer concentration about 65 mM/l . The optimal pH-value for the production of rhamnolipids from n-alkanes or glycerol was in the range pH 6.0-7.2 . While rhamnolipid formation with glycerol as the sole C-source showed a wide optimum ranging from 27 degrees up to 37 degrees C, production of rhamnolipids from n-alkanes had a sharp optimum at 37 degrees C . The addition of multivalent cations, different N-sources and EDTA caused an inhibition of rhamnolipid formation, while the n-alkane concentration had no influence . Specific rhamnolipid formation decreased with increasing cell concentration . Various C-sources were suitable for the formation of rhamnolipids by resting cells of Pseudomonas spec . DSM 2874 . Yields, which were comparable to those obtained on n-alkanes or glycerol, were found for stearic acid, fatty alcohols and vegetable oils . A study of the time course of glycolipid production of resting cells was carried out in a 20 1-bioreactor with an intensor system and with n-tetradecane as the sole C-source. Biosensors, 1985, 1(3), 213 - 320 The development and application of biosensing devices for bioreactor monitoring and control; Clarke DJ et al.; Presently, few of the reported (bio)chemical sensor devices have found application in fermentation monitoring and control . Although many devices with desirable selectivities have been reported, few have demonstrated reliability sufficient to encourage significant and widespread application . Chemical sensors (ion-selective electrodes, amperometric detectors, piezoelectric, field-effect transistors, semiconductor, Optrode and optoelectronic sensors), biosensors (based on potentiometric, amperometric, field-effect transistor and conductiometric detectors) and physical detection methods are reviewed with the aim of highlighting the problems of their application in this area . Physical detection principles appear to show promise as reliable and direct monitoring principles . However, even the more reliable discrete (bio)chemical sensor devices require the development of on-line flow sampling and autocalibration methods to demonstrate the necessary reliability . Biosensor devices appear most problematical and it is concluded that continued development of more direct biosensing principles is likely to prove most fruitful. Dev Biol Stand, 1985, 60, 413 - 9 Production of human interferon-beta in mouse L-cells; Delzer J et al.; A mouse fibroblast cell-constructed by genetic engineering--expresses glycosylated human interferon-beta constitutively . The cells were cultivated on microcarriers in special bioreactors . Under these conditions they produce a maximum yield of 6 000 units interferon-beta/ml/day at cell densities of about 2,2 X 10(6) cells/ml . The production stage of interferon-beta is longer than one month. Immunobiology, 1984 Jan, 166(1), 12 - 23 Production of five human lymphokines (granulocyte-macrophage colony stimulating factor, interferon-gamma, interleukin 2, macrophage cytotoxicity factor and macrophage migration inhibitory factor) from Con A stimulated lymphocyte cultures in bioreactors; Bodeker BG et al.; Cultivation parameters for the production of five lymphokines, granulocyte-macrophage colony stimulating factor (GM-CSF), interferon-gamma (IFN-gamma), interleukin 2 (IL-2), macrophage cytotoxicity factor (MCF), and macrophage migration inhibitory factor (MIF) from human spleen cells or peripheral blood lymphocytes were optimized . Cultivation was done in bioreactors containing up to 200 ml of medium, usually serum-free . The reactors were equipped with surface aeration facilities, stirrers and oxygen electrodes . Whereas stirring speed alone did not influence the yields of lymphokines, good aeration was especially beneficial for high IL-2 yields . However, all lymphokines were also produced under anaerobic conditions . The concentration of the mitogen concanavalin A was mainly critical for optimal IL-2 release . Optimal cell concentrations varied from 5 X 10(6)/ml (for GM-GSF and MCF) to 10 X 10(6)/ml (for IL-2 and IFN-gamma) . It was possible to increase the yields of individual lymphokines 3 to 10-fold per batch of lymphocytes by a reinduction procedure which involved a change of medium and mitogen every 24 hrs . Reinduction was possible up to 4 times, especially when serum was present in the culture media. Int J Artif Organs, 1983 Jul, 6 Suppl 1, 107 - 10 Applications of bioreactors in medicine; Callegaro L et al.; The use of immobilized enzymes, antibodies or reactive proteins was recently considered as a promising approach for detoxification purposes . The appropriate solutions of some specific problems were described and discussed . An hollow fiber haemodialyzer with a membrane surface area of 0.6 m2 was used as standard support for L-asparaginase immobilization . Hemoperfusion columns based on modified agarose beads were also manufactured for the immobilization of antiphenobarbital antibodies. Int J Artif Organs, 1983 Mar, 6(2), 91 - 6 Hollow fiber immobilized L-asparaginase: in vivo and in vitro immunological studies; Callegaro L et al.; The enzyme L-asparaginase was covalently immobilized on the inner surface of the hollow fibers utilized in a commercially available dialyzer by the periodate method . After sterilization with gamma radiation the bioreactor was able to metabolize in vivo, 90 per cent of circulating asparagine in two hours . The absence in blood of asparaginase-related protein fragments, released from the hollow fiber immobilized enzyme, was monitored using a specific enzyme-linked immunosorbent assay (ELISA). J Appl Biochem, 1983 Feb-Apr, 5(1-2), 43 - 52 Construction of glutathione-producing strains of Escherichia coli B by recombinant DNA techniques; Gushima H et al.; The enzymatic production of glutathione (GSH) has been studied in a bioreactor system using toluene-treated cells of Escherichia coli B transformed with recombinant plasmids for gamma-glutamylcysteine synthetase (GSH-I) and glutathione synthetase (GSH-II) . As reported previously the genes for both enzymes were separately cloned onto vector plasmid pBR322 . The plasmid for GSH-I was designated pGS100-2 and that for GSH-II as pGS200 . The effect on GSH production in the bioreactor system, containing an ATP regenerating system, of using cells containing various hybrid plasmids has now been explored . Three kinds of hybrid plasmids, designated pGS300, pGS400, and pGS500, were constructed by subcloning the genes in pGS100-2 and pGS200 onto vector plasmid pBR325 . pGS300 contained the E . coli B chromosomal DNA fragment with a gene for GSH-I in the PstI site of pBR325 . pGS400 also contained E . coli B chromosomal DNA fragment with a gene for GSH-II in the HindIII site of pBR325 . In contrast, pGS500 contained two kinds of DNA fragments with the genes for GSH-I and GSH-II in the PstI and HindIII sites of pBR325, respectively . All the hybrid plasmids thus prepared were stably maintained in E . coli cells when chloramphenicol was included at 10 micrograms/ml in the medium . The activity of the cells containing pGS300 was higher than that of the cells containing pGS400, although the former activity did not come up to that of cells having both pGS300 and pGS400 . The highest glutathione-producing activity was found in the case of the cells transformed with pGS500 carrying both genes for GSH-I and GSH-II on the vector plasmid pBR325 . About 5 mg/ml of glutathione was produced by E . coli cells with pGS500 from 80 mM L-glutamate, 20 mM L-cysteine, and 20 mM glycine within 3 h at 37 degrees C. Biochem Soc Symp, 1983, 48, 221 - 32 Plant cell cloning and culture products; Jones LH; Biotechnological developments in the use of plant cells as sources of biochemicals have now brought several applications within commercial range . Plant propagation has developed faster commercially, but now requires similar biotechnology to enable the automated production of large numbers of plants at low cost . Although some of the enabling technology has been developed for pregerminated seeds this has not been coupled to production of plantlets in bioreactors . Our present lack of knowledge of how to control gene expression in plant cells, which stems from our ignorance of the organization and regulation of the plant genome, is a critical factor limiting all applications of plant cell cultures. Dev Biol Stand, 1983, 55, 241 - 5 Culture conditions for selective and enhanced release of various murine lymphokines (CSF, IL-2, MCF, MIF and TRF); Bodeker BG et al.; The production of the lymphokines colony stimulating factor (CSF), interleukin-2 (IL-2), macrophage cytotoxicity factor (MCF), macrophage migration inhibitory factor (MIF) and T cell replacing factor (TRF) was optimized from mouse spleen cell cultures stimulated with concanavalin A (Con A) . The cultivation was performed in bioreactors which allow regulation of dissolved oxygen concentration . The oxygen supply influenced the yields of individual lymphokines in different ways . High oxygen concentration was beneficial for high release of IL-2 and MCF, whereas MIF and TRF were better produced at low oxygen concentrations . CSF release did not depend on oxygen supply . Upon stimulation with Con A, lymphokine activities in the culture supernatant reached an optimum or plateau after 24 h Lymphocytes continued with lymphokine release, when they were restimulated for further 24 h . in fresh medium and mitogen . CSF could be induced for at least 4 times . MCF was released during the first 3 inductions, whereas IL-2 and TRF were only produced during the first and second induction . These findings led to specific culture conditions for selective and enhanced production of individual lymphokines. Int J Artif Organs, 1981 Mar, 4(2), 102 - 7 Immobilization of arginase on hollow fiber hemodialyzer; Rossi V et al.; The enzyme arginase, purified from bovine liver, was covalently immobilized by the glutaraldehyde method to the inner surface of Cuprophan hollow fibers of a conventional hemodialyzer with a surface 1.3 m3 . The yield of the process was 0.3 microgram/cm2 of active enzyme at physiological pH . The immobilization method did not adversely affect the physical and mechanical properties of hollow fibers neither their hemocompatibility . After sterilization with ethylene oxide, the bioreactor was able to metabolize five liters of 50 microM arginine solution at pH 7.4, in six hours. Int J Artif Organs, 1980 Mar, 3(2), 120 - 3 Immobilization and characterization of L-asparaginase on hollow fibers; Mazzola G et al.; L-Asparaginase was immobilized with various methods: cyanogen bromide, cyanuric chloride and cross-linking with glutaraldehyde . A dialysis device was transformed in a bioreactor with the enzyme immobilized on the outer surface of hollow fibers . Results on kinetic behavior, stability in storage and lyophilization are reported. Biotechnol Bioeng, 1977 Oct, 19(10), 1493 - 501 Electric field control of lipase membrane activity; Karube I et al.; Lipase (EC 3.1.1.3., from Pseudomonas sp.) was entrapped in collagen membrane containing liquid crystal (4-methoxybenzilidene-4'-n-butylaniline) . The activity of the lipase-liquid crystal membrane at an applied voltage of 4 V was 3.4 compared to a membrane tested without imposition of an external electric field . A linear relationship was observed between the activity of the lipase-liquid crystal membrane and the current . The apparent Michaelis constant (K'm) of the lipase-liquid crystal membrane under electric field was identical to that of the membrane under ordinary condition . Activation of the lipase-liquid crystal membrane was observed repeatedly, i.e., activation in the presence of an electric field and reversion to a basal level upon removal of the field occurred cyclically . Activity control of immobilized enzymes is desirable for switching devices of a bioreactor . Possible mechanisms of the lipase activation by electric field are discussed. Biotechnol Bioeng, 1977 Apr, 19(4), 507 - 25 The tubular loop fermentor: oxygen transfer, growth kinetics, and design; Ziegler H et al.; Oxygen transfer measurements using a dynamic method and evaluated with an appropriate mathematical model have been made on a tubular loop bioreactor, Correlations of the type used in tank systmes are used to describe the influence of power and aeration rate on the mass transfer coefficient . Yeast cultures grown on hydrocarbon and glucose substrates show growth characteristics similar to conventional tank results . Model considerations for large-scale tubular fermentors allow for the prediction of the steady-state oxygen profiles and maximum reactor length . Combination with two-phases flow and oxygen transfer correlations yields a design procedure for commercial scale tubular loop fermentors.
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