bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of a tapered fluidized bed as a Continuous bioreactor
Authors: Scott Charles D. , Hancher Charles W. 
Published: December 2004

AbstractReactor systems based on tapered fluidized beds are being developed for aqueous bioprocesses in which adhering microorganisms or immobilized active biological fractions are used. The use of a fluidized bed prevents biomass buildup, accommodates particulates in the feed stream, is compatible with gas sparging, and allows easy removal or addition of the active materials. The tapered reactor tends to stabilize the fluidized bed, thus allowing a much wider range of operating conditions. Preliminary experimental results and an empirical mathematical model of the tapered bed indicate that bed stability is associated with a decreasing velocity and void‐fraction profile up the bed and the pressure drop across the bed decreases with increasing flow rates.The tapered fluidized bed bioreactor is being evaluated for use in the enzymatic production of hydrogen, microbiological denitrification, and microbiological degradation of coal conversion aqueous waste streams. The enzyme catalyzed conversion of lactose to glucose and galactose was used in the evaluation of the reactor concept.
Photosynthetic regeneration of ATP using bacterial chromatophores
Authors: Pace Gary W. , Yang Ho Seung , Tannenbaum Steven R. , Archer Michael C. 
Published: December 2004

AbstractWe have demonstrated the use of bacterial chromatophores for the continuous photosynthetic regeneration of ATP from ADP in an ultrafiltration reactor. Biphasic kinetics of the degradation of chromatophore activity are described. Using chromatophores in combination with the enzyme adenylate kinase, we have also demonstrated continuous regeneration of ATP from AMP.
Preparation and properties of bacterial chromatophores entrapped in polyacrylamide
Authors: Yang Ho Seung , Leung Kwan‐Hang , Archer Michael C. 
Published: December 2004

AbstractThe immobilization of Rhodospirillum rubrum chromatophores was successfully performed by entrapping them in polyacrylamide. Their photophosphorylating activity was about 40% of native chromatophores. The temperature and pH optima for immobilized chromatophores were similar to the native photosynthetic apparatus and kinetic parameters showed that the rate of photophosphorylation in polyacrylamide particles was diffusion controlled. Light penetration of the gel particles was not a limiting parameter. Immobilization considerably increased the stability of the chromatophores towards denaturation.
Automatic membrane‐filtration system for the “on‐demand” supply of large volumes of sterile medium in continuous culture
Authors: Larsen V. F. , Spivey M. , Holdom R. S. 
Published: December 2004

AbstractThe construction and use of an automated membrane filtration system is described which produces 300 liters per day of sterile medium over at least four months of continuous fermentation. The capacity of the system is limited only by choice of filter type and has applications in continuous pilot plant work or medium‐scale batch fermentation, in the bulk supply of communally used laboratory medium, in supplying banks of small‐scale continuous fermentors, and for remote control of medium supply in hazardous fermentations (e.g., methane) with great savings in time and materials. Only two sterile storage jars are needed, irrespective of the total demand for the medium.
An automatic apparatus for continuous suspension culture with a concentrating device
Authors: Schmialek P. , Geyer Astrid , Miosga Verena , Nündel M. , Zapf B. 
Published: December 2004

AbstractA chemostat in which mammalian cells can be raised in continuous suspension culture is described. It is constructed from commercially available parts. This apparatus has the advantage over earlier models in that the medium can be pumped off free of cells, thus suddenly increasing the cell concentration in the culture. The apparatus has been successfully used in studies on contact inhibition.
Oxygen electrode response lag induced by liquid film resistance against oxygen transfer
Authors: Linek V. , Vacek V. 
Published: December 2004

AbstractThe response of a polarographic oxygen electrode to a step change and to an exponential change in bulk oxygen concentration was studied theoretically and experimentally for the case where there is a significant liquid film resistance at the outer side of the membrane‐covered electrode. The probe response has been described by a mathematical model which takes into account the oxygen mass transfer through the liquid film and through the membrane. It is shown that substantial error could be introduced by neglecting the liquid film resistance. A test procedure is suggested to evaluate the error significance.
Immobilization of enzymes based on hydrophobic interaction. II. Preparation and properties of an amyloglucosidase adsorbate
Authors: Caldwell Karin Dahlgren , Axén Rolf , Bergwall Margareta , Porath Jerker 
Published: December 2004

AbstractAmyloglucosidase from Aspergillus niger (α‐1,4 and 1,6 glucan glucohydrolase, EC 3.2.1.3) was immobilized through adsorption onto a hexyl–Sepharose, containing 0.51 mol hexyl‐group per mole of galactose.The adsorption limit of the carrier with respect to this enzyme was about 17 mg per gram wet conjugate. The retention of activity upon immobilization was high, varying from essentially full activity at low enzyme content down to 68% at the adsorption limit.The immobilized preparation, as well as the soluble enzyme, showed apparent zero order kinetics within 60% of the substrate's conversion limit. Product inhibition of the soluble enzyme showed a k1 of 5 · 10−2M.In the presence of 3M NaCl, adsorbates were formed more rapidly and with a higher yield of immobilized protein, but with lower specific activity. Conjugates resulting from adsorption of amyloglucosidase in identical concentrations, but at different salt contents, showed comparable activities and operational stabilities. Continuous operation for three months reduced conjugate activity to 40%.The thermal stability of the adsorbate was inferior to that of the soluble enzyme, but was noticeably enhanced in the presence of substrate.
Immobilization of enzymes based on hydrophobic interaction. III. Adsorbent substituent density and its impact on the immobilization of β‐amylase
Authors: Caldwell Karin Dahlgren , Axén Rolf , Bergwall Margareta , Olsson Ingmar , Porath Jerker 
Published: December 2004

AbstractHexyl‐groups have been introduced into crosslinked Sepharose 6B, yielding gels with degrees of substitution which range from 0.02 to 0.70 mol hexyl‐side chain per mole galactose residue.The gels were exposed to β‐amylase in solution, and the resulting adsorbates indicated a monotonic increase in adsorption capacity with an increasing hexyl‐content. Adsorbate activity, by contrast, displayed a maximum for a carrier gel with a hexyl–galactose ratio of 0.51. Adsorbates based on gels with different hexyl‐content were used in column reactors for continuous maltose production from a soluble starch substrate.
A unique biopolymer from Rhinocladiella mansonii NRRL Y‐6272: Production in 20 liter fermentors
Authors: Burton K. A. , Cadmus M. C. , Lagoda A. A. , Sandford P. A. , Watson P. R. 
Published: December 2004

AbstractThe black yeast‐like fungus Rhinocladiella mansonii NRRL Y‐6272 elaborates an extracellular polysaccharide composed of N‐acetyl D‐glucosamine and N‐acetyl D‐glucosaminuronic acid residues in a 2:1 molar ratio. Production of this polymer was studied in 300 ml flasks and 20 liter fermentors. On the basis of glucose utilized, 13% conversion to polymer was obtained in four days at 25°C in medium containing yeast autolysate paste, K2HPO4, MgSO4, ZnSO4, L‐asparagine or urea, and D‐glucose. Nitrogen sources, aeration, agitation, temperature, and salts affected yields.The polymer in diluted fermentation broths was precipitated with ethanol in the presence of an electrolyte and collected by centrifugation. The viscosities of aqueous resolutions containing 1 and 1.5% of the polymer were 9400 cP and 21,500 cP, respectively.
A method for increasing cellulase production by Trichoderma viride
Authors: Sternberg David 
Published: December 2004

AbstractA doubling of cellulase production by Trichoderma viride (QM9414) is possible by increasing the cellulose concentration in the medium from 0.75 to 2%, increasing the nitrogen concentration, and controlling pH during growth. A four‐to fivefold increase in β ‐glucosidase is found with the higher cellulose concentration. Culture filtrates from 2% cellulose cultures can reduce the hydrolysis time in a practical saccharification to one‐half that required by culture filtrates from 0.75% cellulose cultures.
A silicone polymer as a Steroid Reservoir for enzyme‐catalyzed Steroid reactions
Authors: Bhasin Devinder P. , Gryte Carl C. , Studebaker Joel F. 
Published: December 2004

AbstractSince steroids are only slightly soluble in the aqueous solutions in which enzymatic reactions take place, it is difficult to obtain high effective concentrations per unit reactor volume when enzymes are used to catalyze steroid reactions. In order to obtain high effective concentrations in the present work, we have used small particles of a hydrophobic polymer, poly (dimethyl siloxane), as a reservoir for the steroid substrate and product. The activity of a bacterial hydroxysteroid dehydrogenase in a buffer solution declines much more slowly in the presence of those polymer particles than in the presence of a comparable amount of butyl acetate or ethyl acetate, the organic solvents used as steroid reservoirs in previous work with steroid transforming enzymes. When another substrate of the hydroxysteroid dehydrogenase is loaded into the polymer particles and the particles are suspended in an aqueous solution containing the enzyme and its cofactor, more product is formed that when a similar solution is emulsified with butyl acetate.
Cell concentration control by viscosity
Authors: Shimmons B. W. , Svrcek W. Y. , Zajic J. E. 
Published: December 2004

AbstractThe apparent viscosity of baker's yeast suspensions was employed to control the cell concentration of the mixing of baker's yeast and distilled water. The apparent viscosity of baker's yeast was found to be a function of cell concentration and independent of the flow rate through the rotational viscometer. The viscometer and mixing unit were found to have first order dynamics. The open loop dynamics of the control system were nonlinear but could be linearized for small perturbations. The control system was employed to successfully control the cell concentration but exhibited nonlinear behavior.
Sliding controller design for a nonlinear fermentation system
Authors: Suárez‐Cortez Rodolfo , Alvarez‐Gallegos Jaime , González‐Mora Estela 
Published: December 2004

AbstractThe design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface.
Escherichia coliplasmid production in fermenter
Authors: Reinikainen P. , Korpela K. , Nissinen V. , Olkku J. , Söderlund H. , Markkanen P. 
Published: December 2004

AbstractEscherichia coliharboring a recombinant plasmid was grown in a fermenter to study the effects of selected process parameters on the growth of the microbe and on plasmid amplification with chloramphenicol treatment. Eighteen fermentations were carried out according to a statistical experimental design in which the fermentation temperature, pH, and turbidity of culture at the onset of plasmid amplification were the selected independent process variables. Static regression models describing the process were derived from the experimental results. It turned out that recombinant plasmid copy numbers could be influenced by controlling fermentation temperature and pH. The maximal copy number during bacterial growth phase and the optimal plasmid production were found to require fermentation conditions different from those needed for optimal bacterial growth and cell division. The conditions also differed significantly from those routinely used in research laboratories for plasmid preparation. The chloramphenicol treatment increased the plasmid copy number compared with chromosome numbers up to fivefold. Some of the data suggest that under certain conditions the number of chromosome molecules inE. colicells may rise during the plasmid amplification stage. Statistical experimental design, a nucleic acid sandwich hybridization technique for plasmid quantification, and regression models proved to be useful in this study.
Activity of Pseudomonas aeruginosa in biofilms: Effect of calcium
Authors: Turakhia M. H. , Characklis W. G. 
Published: December 2004

AbstractAerobic glucose metabolism by Pseudomonas aeruginosa biofilms at various calcium loading rates was investigated. The influence of calcium on specific growth rate, extracellular polymeric substance (EPS) formation rate, biofilm detachment rate, and biofilm calcium concentrations was determined. Calcium accumulated in the biofilm in proportion to the liquid phase concentration. Increasing calcium concentration increased the cohesiveness of the biofilm as indicated by a lower relative detachment rate. Specific activity in the biofilm was the same as that measured in a chemostat and was not influenced by changing calcium concentration. EPS formation rate in the biofilm was unaffected by calcium concentration but was higher than that observed in a chemostat.
Data analysis of plasmid maintenance in a CSTR
Authors: San Ka‐Yiu , Weber Allison E. 
Published: December 2004

AbstractA simple procedure is developed to process experimental data from plasmid maintenance studies of recombinant cells in a chemostat with nonselective medium. This procedure, based on the model proposed by Imanaka and Aiba, provides quantitative information on the rate of plasmid loss and the difference in the specific growth rate between the plasmid‐carrying and plasmid‐free cells. The performance of the proposed method is evaluated through simulation studies. In addition, the method is applied to a set of previously reported experimental data. The two‐parameter model, together with the estimated parameter values, provides an excellent fit to the experimental data.
The transient responses of hybridoma cells to nutrient additions in continuous culture: II. Glutamine pulse and step changes
Authors: Miller William M. , Wilke Charles R. , Blanch Harvey W. 
Published: December 2004

AbstractThe transient and steady‐state responses of hybridoma growth and metabolism to glutamine pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The specific glutamine consumption rate increased rapidly after all glutamine additions, but the responses of the glucose and oxygen consumption rates and the cell concentration were found to depend on the intial feed glutamine concentration. The glucose consumption rate was 1.4‐10.9 times that of glutamine, and serine and branched‐chain amino acids were consumed in larger amounts at the higher glucose: glutamine uptake ratios. It was estimated that maintenance accounted for ca. 60% of the cellular ATP requirements at specific growth rates ranging from 0.57 to 0.68 day−1.
Use of culture fluorescence as a sensor for on‐line discrimination of host and overproducing recombinant Escherichia coli
Authors: Walker Colleen C. , Dhurjati Prasad 
Published: December 2004

AbstractThe culture fluorescence of two recombinant Escherichia coli strains with high plasmid copy number were studied and compared to both the host and low copy number varieties of the corresponding strains. Culture fluorescence data are related to the concentration of reduced intracellular nicotinamide adenine dinucleotide within a cell, and can therefore be used as a means for detecting changes in metabolic states. Correlation curves relating culture fluorescence to biomass show that the recombinant system maintains a larger pool of intracellular NADH at high plasmid copy numbers than either the host or the recombinant system at low copy numbers. These results demonstrate the ability of a fluorescence probe to detect differences in the metabolic demands made on an over‐producing recombinant organism.
Effects of carbon and oxygen limitations and calcium concentrations on biofilm removal processes
Authors: Applegate David H. , Bryers James D. 
Published: December 2004

AbstractBacterial biofilm removal processes due to shear and catastrophic sloughing have been investigated in a turbulent flow system under conditions of carbon versus oxygen substrate limitations and varying aqueous phase calcium concentrations. Biofilm cellular and extracellular polymer carbon, total biofilm carbon and mass, and biofilm calcium concentrations are measured for pure culture biofilms of the facultative aerobe, Pseudomonas putida ATCC 11172. Results indicate oxygen‐limited biofilms reach a higher steady‐state biofilm organic carbon level than carbon‐limited biofilms. Oxygen‐limited biofilms also exhibit (1) a higher extracellular polymer‐carbon: cell‐carbon ratio throughout biofilm development and (2) a higher biofilm calcium content than carbon‐limited biofilms. Increasing aqueous phase calcium concentrations increase the amount of biofilm calcium in both cases; the rate of calcium accumulation in oxygen‐limited biofilms increases with increasing liquid phase calcium concentrations over the entire range studied while the rates of calcium accumulation in carbon‐limited biofilms appear independent of aqueous phase calcium concentrations above 11.0 mg/L. Oxygen‐limited biofilms with their higher extracellular polymer and calcium content exhibit shear removal rates that are 20–40% of those observed for carbon‐limited biofilms. However, it is the oxygen‐limited biofilms that experience catastrophic sloughing events. The carbon‐limited biofilms studied here never sloughed even if subjected to intentional long‐term deprivation of all nutrients. Reduced shear removal and the susceptibility to sloughing of the oxygen‐limited biofilms are attributed to their more cohesive structure bought about by their relatively greater extracellular polymer production.
Physiological changes during the adaptation of hybridoma cells to low serum and serum‐free media
Authors: Ozturk Sadettin S. , Palsson Bernhard O. 
Published: December 2004

AbstractTwo murine hybridoma cell lines (167.4G5.3 and S3H5/γ2bA2) were adapted to grow in low‐serum and serum‐free media by a weaning procedure. The changes in cell growth, metabolic, and antibody production rates with adaptation were examined using biochemical and flow cytometric analyses. After adaptation to a particular serum level, the short‐term serum response of the cells was experimentally determined. Specific growth rates, glucose and glutamine uptake and lactate and ammonia production rates, and specific antibody production rates were evaluated from the data. For both cell lines, an improvement in cell growth was observed after adaptation, and both higher growth rates and higher cell concentrations were obtained. The specific glucose and glutamine uptake rates and the lactate and ammonia production rates changed insignificantly with adaptation. Conversely, changes in the specific antibody production rate of the two cell lines differed. Cell line 167.4G5.3 showed a loss in antibody productivity at low serum levels, while the S3H5/γ2bA2 kept its original productivity in low‐serum‐containing media. The intracellular antibody content for S3H5/γ2bA2 cells remained unaltered by adaptation, but a low antibody containing cell population appeared in the 167.4G5.3 culture. The loss of specific antibody productivity in this cell line was due to the appearance of this population.
A model for mercuric ion reduction in recombinant Escherichia coli
Authors: Philippidis George P. , Schottel Janet L. , Hu Wei‐Shou 
Published: December 2004

AbstractPlasmid‐encoded mercuric reduction involves transfer of Hg2+ across the cellular envelope and reduction to Hg0 by the cytoplasmic mercuric reductase using NADPH. A mathematical model was developed for the binding and transfer of Hg2+ by transport proteins and the subsequent reduction of Hg2+. The values of the model parameters were determined using experimental data. The derived rate expressions were similar to the previously experimentally determined ones. The model predicted that a differential amplification of the transport protein relative to mercuric reductase expression levels may enhance the Hg2+ reduction rate in whole cells.
Fermentation conditions for high‐level expression of the tac‐promoter‐controlled calf prochymosin cDNA in Escherichia coli HB101
Authors: Kaprálek F. , Ječmen P. , Sedláček J. , Fábry M. , Zadražil S. 
Published: December 2004

AbstractEscherichia coli HB101 harboring an expression plasmid that bears the calf prochymosin gene controlled by the tac promoter was cultivated under different conditions in order to find an optimal fermentation arrangement that would lead to maximal prochymosin yield. Our results indicate that it is advantageous to use lactose in the double role of inducer and carbon/energy source when foreign gene expression is controlled by the tac promoter and the gene product is only moderately toxic owing to its accumulation in the form of an intracellular body. Glucose, on the other hand, may be used when expression should be repressed. Growth temperature substantially influenced the specific rate of prochymosin and β‐lactamase gene expression and the plasmid copy number. Three phases were distinguished in the time course of the fermentation on lactose: exponential growth practically without prochymosin synthesis, linear growth with prochymosin synthesis, and prochymosin synthesis without growth of biomass. The synthesis of prochymosin in the form of intracellular inclusion body was accompanied by the loss of respiratory activity of the cell and the loss of its ability to multiply. Sixteen hours cultivation at 37°C in a complex medium with lactose as inducer and carbon/energy source resulted in up to 30% of the volume and 48% of the total protein of biomass being accumulated for as prochymosin inclusion bodies. The concentration of extractable enzymatically active chymosin in the culture reached 12 mg/L
Ultrasound‐enhanced bioprocess. II: Dehydrogenation of hydrocortisone by Arthrobacter simplex
Authors: Zabaneh Munder , Bar Raphael 
Published: December 2004

AbstractDehydrogenation of hydrocortisone by agitated suspensions of free and immobilized cells of Arthrobacter simplex ATCC 6946 was investigated under controlled ultrasonic irradiation at a frequency of 20 kHz. The microbial conversion was optimized first with respect to mechanical agitation and subsequently with respect to an additionally superimposed sonication. The optimization of ultrasound intensity and its mode of application were established at a level which maintained the structural integrity of the cells as well as their biocatalytic activity. Various regimes of ultrasound at power densities of 0.030–0.120 W/mL were applied in systems of soluble (0.4 g/L) and excess (1 g/L) hydrocortisone and only a moderate enhancement of the bioconversion by free cells was observed. This result was explained by a better ultrasound‐induced dispersal of microscopic clumps of cells and self‐adhering clusters of the steroids. However, a quite significant enhancement effect was obtained in bioconversion systems of soluble substrate by gel‐entrapped cells. This enhancement was explained by a phonophoretic effect associated with ultrasound‐facilitated diffusion of the substrates—oxygen and hydrocortisone—within the gel beads.