bluuebunny/crossref_metadata_2025_split huggingface dataset:
The immobilization of enzymes and cells of Bacillus stearothermophilus onto poly(maleic anhydride/styrene)–Co‐polyethylene and poly(maleic anhydride/vinyl acetate)–Co‐polyethylene
Authors: Beddows C. G. , Gil H. G. , Guthrie J. T. 
Published: December 2004

AbstractThe graft copolymer, poly(maleic anhydride/styrene)‐co‐polyethylene was prepared. The copolymer immobilized bovine serum albumin (BSA), but the amount coupled appeared to be effected by the amount of styrene in the graft copolymer, temperature, and pH of the coupling medium. Competition existed between hydrolysis of the grafted anhydride groups and the protein. A graft copolymer with 66% add‐on immobilized 4.5 mg/glucose oxidase/g copolymer, 4.6 mg alkaline phosphates/g copolymer and 0.2 mg cell of Bacillus stearothermophilus/g copolymer. A number of copolymers containing poly(maleic anhydride/vinyl acetate)–co‐polyethylene were prepared to cover a range of grafting levels. These immobilized larger quantities of BSA, alkaline phosphatase, and cells of B. stearothermophilus than did the styrene graft copolymer. The copolymer was also hydrolyzed to release the hydroxyl group from the poly(vinyl acetate) component of the grafted chains. Using p‐benzoquinone as the “activating agent,” the copolymer coupled to BSA and to acid phosphatase. Using p‐toluene‐sulfonyl chloride, the copolymer was very effective in immobilizing trypsin.
A mechanistic analysis of the inoculum requirement for the cultivation of mammalian cells on microcarriers
Authors: Hu W. S. , Meier J. , Wang D. I. C. 
Published: December 2004

AbstractFor the cultivation of mammalian cells on microcarriers a minimum inoculum concentration is required to initiate cell attachment and subsequent cell growth. A critical cell number model has been proposed to elucidate the mechanism of the inoculum requirement. In this model it was hypothesized that after inoculation a critical number of cells per microcarrier is required for normal growth to occur; failure to acquire enough cells will impede cell growth. This critical cell number model was expressed mathematically and used to simulate cell distribution and growth on microcarriers under different cultivation conditions. By comparing the simulated growth kinetics with the experimental results, the actual critical cell number per microcarrier was identified. The critical number could be reduced by employing an improved medium for the cultivation.
Filament formation and ethanol production by Zymomonas mobilis in adsorbed cell bioreactors
Authors: Daugulis Andrew J. , Krug T. A. , Choma C. E. T. 
Published: December 2004

AbstractZymomonas mobilis immobilized on microporous ion exchange resins has previously been shown to allow the attainment of high ethanol productivities in packed‐bed bioreactors. The formation of bacterial filaments after several days of continuous operation, however, had resulted in excessive pressure increases across the reactor bed. The present work examines techniques for controlling filament formation by Z. mobilis in two reactor sizes (161 mL and 7.85 L) and a feed glucose concentration of 100 g/L. By controlling the fermentation temperature at 20–25°C it has been possible to eliminate filament formation by Z. mobilis and to operate the larger bioreactor for 232 h with an ethanol productivity of 50 g/L h (based on total reactor volume). The rate of ethanol production has been shown to be very sensitive to temperature in the range 20–30°C, and it is likely that slightly higher temperatures than those used in this study will improve ethanol productivity while still permitting long‐term operation.
The effect of pH on nitrogen supply, cell lysis, and solvent production in fermentations of Clostridium acetobutylicum
Authors: Roos Joseph W. , McLaughlin Joseph K. , Papoutsakis Eleftherios T. 
Published: December 2004

AbstractIn batch fermentations of C. acetobutylicum, with 5 g/L yeast extract and 50mM glucose, the ratio of ammonium to glucose affected solvent production when the pH was left to vary uncontrolled from 4.5 to 3.65. High solvent production was observed for a low ratio. When the pH was controlled at 4.5, only acids were produced for all ratio values. At a low ammonium‐to‐glucose ratio, solvents were produced when the pH was controlled at 3.7. Acids only were produced for a low ratio value at pH 4.0 or for a high ratio value at pH 3.7. In continuous cultures, mostly acids were produced under glucose limitation, but solvents were produced under nitrogen limitation. It was concluded that the nitrogen availability controls solvent production and that the pH affects the availability of organic nitrogen. Biomass autolysis at the stationary phase of batch cultures was reversibly inhibited at pH values less than 3.8. In batch fermentations, the overall molar growth yields on ATP (YATP) varied from 5.5 to 9.0 and the transient yields from 5.5 to 15.5. In continuous cultures, the YATP values varied from 5.5 to 14.7 under glucose limitation, and from 6.1 to 9.3 under nitrogen limitation. The YATP depended on the ammonium to glucose ratio and the culture pH, but did not show the usual dependence on the specific growth rate in batch cultures. The experiments seem to confirm the hypothesis that solvent production is controlled by the demand and availability of ATP.
Scale‐down and optimization studies of the gluconic acid fermentation by Gluconobacter oxydans
Authors: Oosterhuis N. M. G. , Kossen N. W. F. , Olivier A. P. C. , Schenk E. S. 
Published: December 2004

AbstractTo simulate production‐scale conditions of gluconic acid fermentation by Gluconobacter oxydans, different experimental setups are presented in this study. From the determination of the time constants of a production‐scale reactor, it can be concluded that mixing and oxygen transfer are the rate‐limiting mechanisms. This results in oxygen concentration gradients which were simulated in a one‐compartment reactor in which the oxygen concentration was fluctuated by a fluctuated gassing with air and nitrogen. It could be concluded that only very long periods of absence of oxygen (ca. 180 s) results in lower specific oxygen uptake rates by Gluconobacter oxydans. From scale‐down studies carried out in a two‐compartment system to simulate a production‐scale reactor more accurately, it could be concluded that not only the residence time in the aerated part of the system is important, but the liquid flow in between the different parts of the reactor is also an essential parameter. It could also be concluded that the microorganisms are not influenced negatively by the fluctuated oxygen concentrations with respect to their maximal oxidation capacity. The two‐compartment system can also be used for optimization experiments in which the “aerated” compartment was gassed with pure oxygen. From these experiments it was concluded that also a short residence of the cells at high oxygen concentrations diminished the growth and product formation rates. These experiments show the necessity of the scale‐down experiments if optimization is carried out. The two‐compartment system presented in this study is a very attractive tool for reliable scale‐down experiments.
Control of ammonium concentration in Escherichia coli fermentations
Authors: Thompson B. G. , Kole M. , Gerson D. F. 
Published: December 2004

AbstractA control system has been devised for the maintenance of stable ammonium concentrations throughout a fedbatch fermentation. The control system is based on an ammonia gas‐sensing electrode that monitors a pH‐adjusted effluent stream from the fermentor. To overcome the time lag between the fermentor and the electrode, feedback control included metered flows of ammonium to both the fermentor and the electrode vessel. The system was used to study the growth of Escherichia coli B (ATCC 11303) at controlled ammonium concentrations of 5 to 200mM. Apparent specific growth rates, biomass and protein production, and glucose yields were essentially constant from 5 to 170mM. Above 170mM ammonium growth was inhibited. As ammonium concentration decreased from 170 to 5mM, ammonium yields increased from 1 to 24 g cell dry wt/g ammonium utilized. The results demonstrate that control of ammonium concentrations at levels so low that ammonium would be exhausted in batch fermentations can significantly increase overall ammonium yields.
Agitation and pressure effects on acetone‐butanol fermentation
Authors: Doremus Michael G. , Linden James C. , Moreira Antonio R. 
Published: December 2004

AbstractBatch fermentations were run at varying agitation rates and were either pressurized to 1 bar (15.2 psig) or nonpressurized. Agitation and pressure both affect the level of dissolved hydrogen gas in the media, which in turn influences solvent production. In nonpressurized fermentations volumetric productivity of butanol increased as the agitation rate decreased. While agitation had no significant effect on butanol productivity under pressurized conditions, overall butanol productivity was increased over that obtained in the nonpressurized runs. Maximum butyric acid productivity, however, was found to occur earlier and increased as agitation increased. Peak hydrogen productivity occurred simultaneously with peak butyric acid productivity. The proporation of reducing equivalents used in forming the above products was determined using a redox balance based on the fermentation stoichiometry. An inverse relationship between the final concentrations of acetone and acetoin was found in all fermentations studied. The results show that agitation and pressure are important parameters for solvent productivity in acetone‐butanol fermentation.
Enhanced polysaccharide recovery from agricultural residues and perennial grasses treated with alkaline hydrogen peroxide
Authors: Gould J. Michael 
Published: December 2004

AbstractPretreatment of lignocellulosic materials with alkaline hydrogen peroxide greatly increases their susceptibility to enzymatic cellulose hydrolysis. During the course of the pretreatment reaction (18 h), the pH rises slowly, increasing from pH 11.5 to a final pH > 12. As a result, most of the hemicellulose in the lignocellulosic substrate becomes solubilized. Maintaining the reaction pH near the optimum of 11.5 prevents hemicellulose solubilization and decreases the time required for effective pretreatment to about 6 h. Alkaline peroxide pretreatment is most effective on lignocellulose from monocotyledonous plants, especially members of the family Gramineae. Enzymatic saccharification efficiencies > 90% of theoretical were attained from high yielding perennial grasses such as big bluestem (Andropogon gerardi) and Indian grass (Sorghastrum nutans) after alkaline peroxide pretreatment.
The β‐xylosidase of Thermomonospora
Authors: Ristroph D. L. , Humphrey A. E. 
Published: December 2004

AbstractThis study is concerned with characterizing cell‐bound inducible β‐xylosidase produced by a strain of the thermophilic bacterial genus Thermomonospora. A crude preparation of this enzyme recovered from sonicated cells of this organism displayed high activity against paranitrophenyl‐β‐xylopyranoside over a pH range of 5.5‐7.7. The temperature optimum, based on a 30‐min assay of activity, at pH 6.5 was 70°C. The crude enzyme had a thermal half‐life of approximately 1 week at 55°C and pH 6.5. Xylose inhibited the enzyme. Values of Km and Vmax are estimated from the reaction rate data as 0.82 mM and 8 U/L, respectively.
An immobilized cell reactor with simultaneous product separation. I. Reactor design and analysis
Authors: Dale M. C. , Okos M. R. , Wankat P. C. 
Published: December 2004

AbstractA four‐phase reactor–separator (gas, liquid, solid, and immobilized catalyst) is proposed for fermentations characterized by a volatile product and nonvolatile substrate.In this reactor, the biological catalyst is immobilized onto a solid column packing and contacted by the liquid containing the substrate.A gas phase is also moved through the column to strip the volatile product into the gas phase. The Immobilized Cell Reactor–Separator (ICRS) consists of two basic gas–liquid flow sections: a cocurrent “enricher” followed by a countercurrent–“stripper”.In this article, an equilibrium stage model of the reactor is developed to determine the feasibility and important operational variables of such a reactor–separator. The ICRS concept is applied to the ethanol from whey lactose fermentation using some preliminary immobilized cell reactor performance data. A mathematical model for a steady‐state population based on an adsorbed monolayer of cells is also developed for the reactor. The ICRS model demonstrated that the ICRS should give a significant increase in reactor productivity as compared to an identically sized Immobilized Cell Reactor (ICR) with no separation. The gas‐phase separation of the product also allows fermentation of high inlet substrate concentrations. The model is used to determine the effects of reactor parameters on ICRS performance including temperature, pressure, gas flow rates, inlet substrate concentration, and degree of microbial product inhibition.
An immobilized cell reactor with simultaneous product separation. II. Experimental reactor performance
Authors: Dale M. C. , Okos M. R. , Wankat P. C. 
Published: December 2004

AbstractThe simultaneous separation of volatile fermentation products from product‐inhibited fermentations can greatly increase the productivity of a bioreactor by reducing the product concentration in the bioreactor, as well as concentrating the product in an output stream free of cells, substrate, or other feed impurities. The Immobilized Cell Reactor–Separator (ICRS) consists of two column reactors: a cocurrent gas–liquid “enricher” followed by a countercurrent “stripper” The columns are four‐phase tubular reactors consisting of (1) an inert gas phase, (2) the liquid fermentation broth, (3) the solid column internal packing, and (4) the immobilized biological catalyst or cells. The application of the ICRS to the ethanol‐from‐whey‐lactose fermentation system has been investigated. Operation in the liquid continuous or bubble flow regime allows a high liquid holdup in the reactor and consequent long and controllable liquid residence time but results in a high gas phase pressure drop over the length of the reactor and low gas flow rates. Operation in the gas continuous regime gives high gas flow rates and low pressure drop but also results in short liquid residence time and incomplete column wetting at low liquid loading rates using conventional gas–liquid column packings. Using cells absorbed to conventional ceramic column packing (0.25‐in. Intalox saddles), it was found that a good reaction could be obtained in the liquid continuous mode, but little separation, while in the gas continuous mode there was little reaction but good separation. Using cells sorbed to an absorbant matrix allowed operation in the gas continuous regime with a liquid holdup of up to 30% of the total reactor volume. Good reaction rates and product separation were obtained using this matrix. High reaction rates were obtained due to high density cell loading in the reactor. A dry cell density of up to 92 g/L reactor was obtained in the enricher. The enricher ethanol productivity ranged from 50 to 160 g/L h while the stripper productivity varied from 0 to 32 g/L h at different feed rates and concentrations. A separation efficiency of as high as 98% was obtained from the system.
Mathematical modelling of growth and substrate conversion of Zymomonas mobilis at 30 and 35°C
Authors: Jöbses I. M. L. , Egberts G. T. C. , van Baalen A. , Roels J. A. 
Published: December 2004

AbstractZymomonas mobilis was grown in continuous cultures at 30 and 35°C. The specific substrate consumption rates at 35°C were higher than those at 30°C. An unstructured mathematical model based on the linear equation for substrate consumption provided a statistically adequate description for cultures grown at 35°C but not for cultures grown at 30°C. A structured two‐compartment model described growth and substrate consumption well at both temperatures. Some theoretical and practical aspects of the two‐compartment model are discussed.
Microcalorimetric study of cellulose degradation by Cellulomonas uda ATCC 21399
Authors: Dermoun Z. , Belaich J. P. 
Published: December 2004

AbstractA newly designed batch calorimeter was used to investigate the degradability of some celluloses having varying degrees of crystallinity. The PTC of an aerobic culture of Cellulomonas uda ATCC 21399 obtained revealed a diauxic growth which is attributed to the presence of hemicellulose contaminating Avicel and MN300 cellulose. The microcrystalline celluloses used were not completely utilized, whereas amorphous cellulose was easily metabolized, indicating that under the growth conditions used here, the physical structure of cellulose strongly influenced its microbial degradability. An equivalent growth yield of ca. 0.44 g/g was found with all the substrates used. The heat evolved by metabolism of 1 g cellulose was ‐5.86 kJ/g, a value similar to that obtained with glucose culture. The growth rate was the only variable parameter. The data obtained showed as expected that the hydrolysis product of cellulose was consumed in the same way as that of glucose and that the only limiting factor to the biodegradability of cellulose was the breakdown of the polymeric substrate. It is concluded that data obtained with glucose metabolism can be used to evaluate the extent of cellulose degradation.
Shear stress effects on human embryonic kidney cells in Vitro
Authors: Stathopoulos N. A. , Hellums J. D. 
Published: December 2004

AbstractHuman embryonic kidney cells grown as an attached, confluent monolayer on a flat substrate were subjected to steady, uniform laminar flow of medium in a specially designed chamber in which flow patterns and shear stress are accurately defined and controlled. Experiments were performed for shear stress levels ranging from 0.2 to 6.0 N/m2 with times of exposure to the shear stress ranging from 2 to 24 h. The influence of the shear field was slight at low shear stress (0.26 N/m2). Higher stress levels (0.65 N/m2 and higher) had significant effects on cell morphology, and on the post‐shear release of urokinase enzyme. Still higher stress levels (2.6 N/m2 and higher) caused marked reduction in cell viability. These results may be of interest in addressing practical problems in developing commercial biosynthesis reactors.
Enzymatic hydrolysis of cellulose in aqueous two‐phase systems. I. partition of cellulases from Trichoderma reesei
Authors: Tjerneld Folke , Persson Ingrid , Albertsson Per‐Åke , Hahn‐Hägerdal Bärbel 
Published: December 2004

AbstractThe partitioning of endo‐β‐glucanase, exo‐β‐glucanase, and β‐glucosidase from Trichoderma reesei QM 9414 in aqueous two‐phase systems has been studied with the object of designing a phase system for continuous bioconversion of cellulose. The partitioning of the enzymes in two‐phase systems composed of various water soluble polymeric compounds were studied. Systems based on dextran and polyethylene glycol (PEG) were optimal for one‐sidedly partitioning the enzymes to the bottom phase. The influence of polymer molecular weights, polymer concentration, ionic composition of the medium, pH, temperature, and adsorption of the enzymes to cellulose on the enzyme partition coefficients (K) were studied. By combining the effects of polymer molecular weight and adsorption to cellulose, K values could be reduced for endo‐β‐glucanase to 0.02 and for β‐glucosidase to 0.005 at 20°C in a phase system of Dextran 40–PEG 40000 in the presence of excess cellulose, At 50°C, K values were increased by a factor of two. In a phase system based on inexpensive crude dextran and PEG, the partition coefficient for endo‐β‐glucanase was 0.16 and for β‐glucosidase was 0.14 at 20°C with excess cellulose present.
Fermentation of cellodextrins to ethanol using mixed‐culture fermentations
Authors: Freer S. N. , Wing R. E. 
Published: December 2004

AbstractThe potential for enhancing ethanol production from cellodextrins by employing mixed‐culture (Candida wickerhamii–Saccharomyces cerevisiae) fermentations was investigated. Initially, ethanol production was monitored in fermentation medium containing 50 g/L glucose plus 45 g/L cellobiose. Inoculum levels and times of inoculum addition were varied. Of the conditions tested, the most rapid rates of ethanol formation occurred in fermentations in which either C. wickerhamii and S. cerevisiae were coinoculated at a ratio of 57 : 1 cell/mL or in fermentations in which a 10‐fold‐greater S. cerevisiae inoculum was added to a pure culture C. wickerhamii fermentation after 1 day incubation. These conditions were used to attempt to enhance fermentations in which cellodextrins produced by trifluoroacetic acid hydrolysis of cellulose served as the sole carbon source. Cellodextrins that were not further purified after cellulose hydrolysis contained compounds that were slightly inhibitory to C. wickerhamii. In this case the mixed‐culture fermentations produced 12–45% more ethanol than a pure culture C. wickerhamii fermentation. However, if the substrate was treated with Darco G‐60 charcoal, the toxic materials were apparently removed and the pure culture C. wickerhamii fermentations performed as well as the mixed‐culture fermentations.
Gas holdup in an external‐loop air‐lift fermentor with a contaminated gas distributor
Authors: McManamey W. J. , Wase D. A. J. , Raymahasay S. 
Published: December 2004

AbstractContamination of the porous‐plate gas distributor was observed in an air‐lift fermentor used for Aspergillus fumigatus fermentations. Comparisons between gas holdups measured with uncontaminated distributors and the contaminated one showed that the contamination had no effect on gas holdups in water but reduced the holdups in sodium chloride and sodium sulfate solutions, probably due to increased bubble coalescence. A correlation for gas holdups with clean distributors2 could be used to represent the results for the comtaminated distributor by changing the values used for the characteristic velocities of the electrolyte solutions.
Entrapment of concanavalin A‐glycoenzyme complexes in calcium alginate gels
Authors: Husain Qayyum , Iqbal Jawaid , Saleemuddin M. 
Published: December 2004

AbstractGlucose oxidase, invertase, and amyloglucosidase were entrapped in calcium alginate gels as concanavalin A complexes in order to prevent the leaching out of the enzymes from the porous matrix. The free as well as the gel‐entrapped concanavalin A‐glycoenzyme complexes exhibited a relatively high effectiveness factor, η, indicating good accessibility to the substrates. Concanavalin A‐invertase complex exhibited marked broadening of pH‐activity and temperature‐activity profiles and was highly resistant to temperature inactivation even after entrapment in the alginate beads. It was possible to entrap considerable quantities of invertase as concanavalin A complex in the beads without a marked decrease in η. A column containing crosslinked concanavalin A‐invertase complex entrapped in alginate beads retained the ability to completely hydrolyze 1M sucrose even after continuous operation for over four months.
Aspartate glucan, glycine glucan, and serine glucan for the removal of cobalt and copper from solutions and brines
Authors: Muzzarelli Riccardo A. A. , Tanfani Fabio , Emanuelli Monica , Bolognini Luigi 
Published: December 2004

AbstractAspartate glucan, glycine glucan, and serine glucan obtained by reductive amination of oxalacetic acid, glyoxylic acid, and β‐hydroxypyruvic acid, respectively, with polyglucosamine were tested as chromatographic chelating media. Crosslinked glycine glucan exhibited high capacities for cobalt and copper, even in acidic solutions (pH 2.9). Breakthrough points for 10 mg/L solutions through 6.0 × 0.6 cm columns containing 200 mg of polymer were at 1.8 L for both ions; for 1 mg/L solutions, they were at 4.0 and 12.0 L for cobalt and copper, respectively. Crosslinked glycine glucan could remove microgram amounts of cobalt and copper from fluoride and chloride brines. Cobalt and copper could be separated by elution with 0.25M sulfuric acid.