bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic resolution of racemic glycidyl butyrate using a multiphase membrane enzyme reactor: Experiments and model verification
Authors: Wu Dauh‐Rurng , Cramer Steven M. , Belfort Georges 
Published: December 2004

AbstractA laboratory‐scale multiphase hollow fiber membrane reactor was employed to investigate the lipase‐catalyzed enzymatic resolution of racemic glycidyl butyrate. A mathematical formulation was feveloped to simulate the performance of this system. Model parameters were determined independently (except the effective rate constant, ks) and incorporated in the model simulations. In this study, two modes of operation are considered: subtractive resolution, in which the unreacted substrate is recovered in the organic stream; and product recovery, where the optically pure product of the enzymatic reaction is recovered in the aqueous stream. Good agreement was obtained between theoretical predictions and experimental results under a variety of conditions. The effect of mass transport limitations on the performance of this system was investigated. An increase in enzyme loading resulted in a higher Thiele modulus due to an elevated rate constant as well as a concomitant decrease in the effective diffusivity. Optical purity decreased in both subtractive resolution and product recovery at higher Thiele modulus with the effect being more pronounced in the product recovery mode. Finally, normalized plots were established to describe the effect of enzyme immobilization on both the effective enzymes activity and effective diffusivity. © 1993 Wiley & Sons, Inc.
Sterilization of various diameter dead‐ended tubes
Authors: Young Jack H. 
Published: December 2004

AbstractEffect of tube diameter on steam‐in‐place sterilization of dead‐ended tubes was studied by examining temperature profiles and rates of kill of Bacillus stearothermophilus spores. Time required for sterilization was determined for 9.4‐cm‐long tubes with various inside diameters from 0.4 to 1.7 cm. Sterilization time increased with decreasing tube diameter. Experimentally measured kill kinetics in 1.7‐cm tubes were in agreement with those predicted if measured temperatures represented saturated steam. A 12‐log spore reduction was achieved in 1.7‐cm diameter vertical and horizontal tubes in less than 63 minutes. For smaller diameter tubes, entrapped air remained after 2 hours and rates of kill were very dependent on position within the tube, tube diameter, and tube orientation with respect to the gravitational vector. Times to achieve a 1‐log drop in spore population in the smaller tubes were as much as 10 times greater than those expected if measured temperatures represented saturated steam. Sterilization was not achieved throughout the 0.4–cm tubes. Recommendations are made for including steam bleeders or using prevaccum cycles for these smaller diameter tubes. © 1993 John Wiley & Sons, Inc.
Cell retention–chemostat studies of hybridoma cells—analysis of hybridoma growth and metabolism in continuous suspension culture in serum‐free medium
Authors: Hiller G. W. , Clark D. S. , Blanch H. W. 
Published: December 2004

AbstractThe steady‐state metabolic parameters for a hybridoma cell line have been determined in continuous suspension–perfusion culture over a wide range of perfusion rates and cell bleed rates. Significant increases in viable cell concentrations and volumetric productivities were achieved at high perfusion rates and low cell bleed rates. At the low growth rates examined in this study, cellular metabolism shifted to become more oxidative, and as a result, the fraction of consumed substrate converted to inhibitory metabolic by‐products was reduced. Specific antibody productivity was found to be non–growth associated. © 1993 John Wiley & Sons, Inc.
Lipase activity in vesicular systems: Characterization of candida cylindracea lipase and its activity in polymerizable dialkylammonium surfactant vesicles
Authors: Mosmuller E. W. J. , Franssen M. C. R. , Engbersen J. F. J. 
Published: December 2004

AbstractLipase from Candida cylindracea (CCL) was incorporated into polymerizable positively charged dialkylammonium bromide surfactant vesicles. The enzyme was incorporated by the use of the dehydration–rehydration method or by incubation. In the latter case, trapping efficiencies of up to 100% could be obtained. Activities of free and vesicle‐incorporated CCL were tested for three triglycerides: triacetin, tributyrin, and tricaprylin. Enzyme activity was lowest in homogeneous mixtures (triacetin and small concentrations of tributyrin) and highest in heterogeneous mixtures (tricaprylin and high concentrations of tributyrin). Entrapment in vesicular systems is advantageous, especially in homogeneous reaction mixtures and in the case of the production of insoluble fatty acid (caproate), because inhibition by the acid can be suppressed. The influence of several surface‐active additives, including vesicles, on the activity of lipase in triglyceride assays was tested. Vesicles have a positive influence on the activity, whereas other positively charged additives act as inhibitors. In the case of tricaprylin assays, the positively charged additives increase the activity. Finally, tryptic digestion for free and incorporated CCL were compared. Free CCL is readily inactivated, whereas incorporated enzyme is protected from proteolytic degradation. © 1993 John Wiley & Sons, Inc.
Fed‐batch cultivation of recombinant escherichia coli JM103 and production of the fusion protein SPA::EcoRI in a 60‐L working volume airlift tower loop reactor
Authors: Brandes Lutz , Wu Xiaoan , Bode Jens , Rhee Jong II , Schügerl Karl 
Published: December 2004

AbstractSPA::EcoRI fusion protein was produced by Escherichia coli JM103 carrying the multicopy expression plasmid pMTC48, the multicopy repressor plasmid pRK248, and the multicopy protection plasmid pEcoR4 in a 60‐L working volume airlift tower loop reactor on M9 minimal medium with glucose. Cell mass concentration, total cell count, number of colony‐forming units, specific growth rate, yield coefficient, and metabolite (acetate, pyruvate, succinate, lactate, ethanol) concentrations were monitored during the growth phase and gene expression. Gene expression was induced by temperature shift or chemically by isopropyl‐thiogalactosidase in the airlift tower loop reactor (ALTR) at constant cultivation time and in a small stirred tank reactor at different cultivation times. During induction, the cultivation medium was supplemented with concentrated Luria–Bertani (LB) medium. The intracellular enzyme activity was evaluated as a function of the time after the start of the induction. It was found that the reduction of the glucose concentration and increase of the dissolved oxygen concentration reduced the acetate produced and increased the intracellular enzyme activity. © 1993 John Wiley & Sons, Inc.
Expression of epoxide hydrolase in insect cells: A focus on the infected cell
Authors: Wang Min‐Ying , Vakharia Vikram , Bentley William E. 
Published: December 2004

AbstractInsect cell culture and the baculovirus vector expression system have emerged to be a promising production technique for heterologous proteins. In this article, expression characteristics for membrane‐bound epoxide hydrolase are examined. A generic process is presented whereby cells are grown in serum‐free media supplemented with serum and then resuspended in serum‐free media to simplify purification after infection. The infected cells retain significant metabolic activity during the postinfection stage. Thus, maintaining nutrient supply during the postinfection period is critical, and a low stirring rate will result in oxygen depletion and shift the metabolism of the infected cells toward lactate production which then lowers product yield. This is the first report indicating that glucose is supplied from sucrose decomposition and then metabolized for viral DNA and recombinant protein production in recombinant baculovirus insect expression system. © 1993 John Wiley & Sons, Inc.
Subzero temperature operating biosensor utilizing an organic solvent and quinoprotein glucose dehydrogenase
Authors: Sode Koji , Nakasono Satoshi , Tanaka Mitsuharu , Matsunaga Tadashi 
Published: December 2004

AbstractA subzero temperature operating biosensor was constructed using immobilized quinoprotein glucose dehydrogenase (PQQGDH), glassy carbon electrode, soluble electron mediator (ferrocene monocarboxylic acid), and an organic solvent, ethylene glycol, as an antifreezing reagent. Using this biosensor, glucose concentration can be determined even at −7°C. At this temperature, the response was 20% of that obtained at 20°C. This is the first study describing a subzero temperature operating biosensor. © 1993 John Wiley & Sons, Inc.
Esterification of N‐benzyloxycarbonyldipeptides in ethanol–water with immobilized papain
Authors: Kawashiro Katsuhiro , Ishizaki Hideyuki , Sugiyama Shigeru , Hayashi Hiromu 
Published: December 2004

AbstractThe esterification of some N‐benzyloxycarbonyl (Z)‐dipeptides in ethanol‐containing water was investigated using papain as a catalyst. The esterification took place in ethanol containing a samll amount of water (2% v/v, pH 9) with free papain at room temperature. The yield (after 24 h) of the ethyl ester was in the range of 25% to 50%. Any peptide bond cleavage of the substrates was not observed during esterification, indicating that the unfavorable amidase activity of papain was well depressed under these conditions. However, dipeptides having a D‐amino amino acid (Z‐valyl‐D‐alanine) or a bulky amino acid (Z‐valylvaline) at the C‐terminal position could not be esterified. It was found that the immobilization of papain on Amberlite XAD‐8 increased the yield of the ester significantly as compared with free papain. In the esterification of Z‐valylalanine using immobilized papain, the optimum water content, pH of an added buffer, and temperature were found to be 2% (v/v), 9, and 40°C, respectively. The water content affected the yield of the product ester significantly.© 1993 John Wiley & Sons, Inc.
Kinetic models for synthesis by a thermophilic alcohol dehydrogenase
Authors: Ford Jonathan B. , Askins K. Janine , Taylor Kenneth B. 
Published: December 2004

AbstractAlcohol dehydrogenase (E. C. 1.1.1.1) from Thermoanaerobium brockii at 25°C and at 65°C is more active with secondary than primary alcohols. The enzyme utilizes NADP and NADPH as cosubstrates better than NAD and NADH. The maximum velocities (Vm) for secondary alcohols at 65°C are 10 to 100 times higher than those at 25°C, whereas the Km values are more comparable.At both 25°C and 65°C the substrate analogue 1,1,1,3,3,3‐hexafluoro‐2‐propanol inhibited the oxidation of alcohol competitively with respect to cyclopentanol, and uncompetitively with respect to NADP. Dimethylsulfoxide inhibited the reduction of cyclopentanone competitively with respect to cyclopentanone, and uncompetitively with respect to NADPH. As a product inhibitor, NADP was competitive with respect to NADPH. These results demonstrate that the enzyme binds the nucleotide and then the alcohol or ketone to form a ternary complex which is converted to a product ternary complex that releases product and nucleotide in that order.At 25°C, all aldehydes and ketones examined inhibited the enzyme at concentrations above their Michaelis constants. The substrate inhibition by cyclopentanone was incomplete, and it was uncompetitive with respect to NADPH. Furthermore, cyclopentanone as a product inhibitor showed intercept‐linear, slope‐parabolic inhibition with respect to cyclopentanol. These results indicate that cyclopentanone binds to the enzyme–NADP complex at high concentrations. The resulting ternary complex slowly dissociates NADP and cyclopentanone.At 65°C, all of the secondary alcohols, with the exception of cyclohexanol, show substrate activation at high concentration. Experiments in which NADP was the variable substrate and cyclopentanol as the constant–variable substrate over a wide range of concentrations gave double reciprocal plots in which the intercepts showed substrate activation and the slopes showed substrate inhibition. These results indicate that the secondary alcohols bind to the enzyme–NADPH complex at high concentrations and that the resulting ternary complex dissociates NADPH faster than the enzyme–NADPH complex. © 1993 John Wiley & Sons, Inc.
Bioconversion of lactose/whey to fructose diphosphate with recombinant saccharomyces cerevisiae cells
Authors: Compagno C. , Tura A. , Ranzi B. M. , Martegani E. 
Published: December 2004

AbstractGenetically engineered Saccharomyces cerevisiae strains that express Escherichia coli β‐galactosidase gene are able to bioconvert lactose or whey into fructose‐1,6‐diphosphate (FDP). High FDP yields from whey were obtained with an appropriate ratio between cell concentration and inorganic phosphate. The biomass of transformed cells can be obtained from different carbon sources, according to the expression vector bearing the lacZ gene. We showed that whey can be used as the carbon source for S. cerevisiae growth and as the substrate for bioconversion to fructose diphosphate. © 1993 John Wiley & Sons, Inc.
Immobilized Coffea arabica cell culture using a bubble‐column reactor with controlled light intensity
Authors: Kurata Hiroyuki , Furusaki Shintaro 
Published: December 2004

AbstractCoffea arabica cells immobilized by calcium alginate gel were photocultured using a bubble‐column reactor under controlled light intensity. This process was carried out after their alkaloid productivity was improved by increasing the cell density in the initial gel matrix and preculturing the immobilized cells in the dark prior to light irradiation. The cells were grown in the form of a biofilm on gel beads, producing 100 mg/L of purine alkaloids in a 24‐day batch culture. Alkaloid production was relatively constant with respect to light intensity changes, and also cell growth was not suppressed much at high light intensity, with these behaviors being different from those obtained using suspended cells. These phenomena are explained by estimating the light intensity gradient within the cell‐immobilizing particles and by measuring the viable cell distribution within them. It subsequently suggests that the subsurface cells affect both the production and growth behaviors. © 1993 John Wiley & Sons, Inc.
Extractive separation of penicillin G by facilitated transport via carrier supported liquid membranes
Authors: Lee Chau‐Jen , Yeh Huey‐Jiuan , Yang Wu‐Jung , Kan Chin‐Rang 
Published: December 2004

AbstractThe facilitated transport of penicillin G (Pen G), through a supported liquid membrane with Amberlite LA‐2 dissolved in 1‐decanol, supported on a microporous polypropylene membrane, were studied. The distribution coefficient was obtained from a batch extraction experiment. The effects of flow rate, carrier concentration, initial concentration of Pen G, and the pH of feed and stripping phases on the transport rate of Pen G through the supported liquid membrane were also investigated. The results are in agreement with theoretical predictions, and it is demonstrated that the transport of Pen G through the supported liquid membrane is controlled simultaneously by mass transfer across both aqueous and liquid membranes. © 1993 John Wiley & Sons, Inc.
Substantial overproduction of antibodies by applying osmotic pressure and sodium butyrate
Authors: Oh Steve K. W. , Vig Pooja , Chua Florence , Teo W. K. , Yap Miranda G. S. 
Published: December 2004

AbstractMuch of the current cell technology has enabled increased antibody production levels due to judicious nutrient feeding to raise cell densities and design better bioreactors. This study demonstrates that hybridomas can be hyperstimulated to produce higher immunoglobulin (lg) levels by suppressing cell growth and increasing culture longevity through adaptation to higher osmolarity media and addition of sodium butyrate. Prior to adaptation, cells placed in higher osmotic pressures (350 and 400 mOsm) were severely suppressed in growth down to 25% of the control (300 mOsm), although total lg titers achieved were similar to the control, approximately 140 mg/L. After a week of adaptation to 350 and 400 mOsm media, cell growth was not as dramatically suppressed, but considerably higher lg levels were attained at these elevated osmolarities. The highest yield of 265 mg/L was obtained at 350 mOsm compared to 140 mg/L at 300 mOsm, while maximum viable cell numbers dropped from 35 × 105 cells/mL to 31 × 105 cells/mL and culture longevity was extended by 20 h more than the control. Sodium butyrate, known to enhance protein production in other cell types, was then supplemented at a range of concentrations between 0.01 and 0.4 mM to the 350 mOsm culture to further enhance the lg levels. Butyrate at a concentration of 0.1 mM, in combination with osmotic pressure at 350 mOsm, further elevated the lg levels to 350 mg/L. Concomitantly, maximum viable cell numbers were reduced to 22 × 105 cells/mL, but culture longevity was extended by 40 h in the 0.1 mM butyrate supplemented culture compared to the control condition. Specific antibody productivity, qMab, continued to stay high during the stationary phase and was further elevated during the decline phase: thus, overall lg levels can be increased by 2.3 times by combining osmotic pressure and butyrate treatment. © 1993 John Wiley & Sons, Inc.
Response dynamics of 26‐, 34‐, 39‐, 54‐, and 80‐kDa proteases in induced cultures of recombinant Escherichia coli
Authors: Harcum Sarah W. , Bentley William E. 
Published: December 2004

AbstractSeveral researchers have demonstrated that the presence of a heterologous protein in recombinant Escherichia coli elicits a response similar to the heat‐shock response, which includes enhanced protease expression. The present work detects, quantifies, and characterizes intracellular protease activity in E. coli that are “shocked” by the induction of a recombinant protein, CAT, which is an endogenous protein in some E. coli strains. A novel, sodium dodecyl sulfate gelatin poly‐acrylamide gel electrophoresis (SDS‐GPAGE) method is used to detect, quantify, and characterize the presence of these proteases. A hypothesis is proposed which links the amplified protease activity to a temporary depletion of specific amino acid pools, and a stringent‐like stress response. © 1993 John Wiley & Sons, Inc.
Utilization of glucose and amino acids in insect cell cultures: Quantifying the metabolic flows within the primary pathways and medium development
Authors: Ferrance Jerome P. , Goel Akshay , Ataai Mohammad M. 
Published: December 2004

AbstractThe current understanding of insect cell metabolism is very limited. In order to gain some insight into the growth and metabolism of insect cells Spodoptera frugiperda (Sf9), a comprehensive characterization of culture conditions for cells grown in the IPL‐41 medium was made by measuring the amino acid composition of the growth medium and the cell extract, the macromolecular composition of the cells (DNA, RNA, and protein), medium concentrations of various metabolites and sugars, and the evolved CO2. Since in the IPL‐41‐based serum‐free medium all of the amino acids except cysteine are in great excess of what is needed by the cells for energy and protein production, a medium formulation with an osmolarity similar to the IPL‐41 but with a lower amino acid content than IPL‐41 was also developed. The new medium also lacks maltose and sucrose (contains only glucose), supported cell growth to a high cell density of 8 × 106 cells/mL. The cellular and energetic yields indicated that a tight coupling between the biosynthetic and energetic reactions was attained for cells grown in the new medium. Moreover, it was found that the intermittent feeding of glucose may not be required as the cell yield and growth rate were comparable whether the same total amount of glucose was provided intermittently or was included initially in the medium. The eventual cessation of growth in the new medium is believed to be due to the amino acid limitation because concentrations of both glutamine and glutamate were very low at the end of the growth phase. Thus, further optimization, which may include higher initial glutamine in the medium or its intermittent feeding, could lead to a further increase in the cell density. Finally, a stoichiometrically based analysis of metabolic reactions confirmed the operation of the key pathways and was used to quantify the distribution of metabolites among primary metabolic reactions. The quantitative flow values were used to highlight some key aspects of insect cell metabolism. © 1993 John Wiley & Sons, Inc.
Removal of phenols from wastewater by soluble and immobilized tyrosinase
Authors: Wada Shinji , Ichikawa Hiroyasu , Tatsumi Kenji 
Published: December 2004

AbstractAn enzymatic method for removal of phenols from industrial wastewater was investigated. Phenols in an aqueous solution were removed after treatment with mushroom tyrosinase. The reduction order of substituted phenols is catechol > p‐cresol > p‐chlorophenol > phenol > p‐methoxyphenol. In the treatment of tyrosinase alone, no precipitate was formed but a color change from colorless to dark‐brown was observed. The colored products were removed by chitin and chitosan which are available abundantly as shellfish waste. In addition, the reduction rate of phenols was observed to be accelerated in the presence of chitosan. Tyrosinase, immobilized by using amino groups in the enzyme on cation exchange resins, can be used repeatedly. By treatment with immobilized tyrosinase, 100% of phenol was removed after 2 h, and the activity was reduced very little even after 10 repeat treatments. © 1993 John Wiley & Sons, Inc.
Comments on “in search of a thermodynamic description of biomass yields for the chemotrophic growth of microorganisms”
Authors: Roels J. A. 
Published: December 2004

AbstractIn a recent publication, Heijnen and van Dijken (Biotechnol. Bioeng. 39: 833–858, 1992) reviewed the state of the art regarding the use of macroscopic methods in the correlation of biomass yields in growing microorganisms. In their article, reference is made to this author's work of some 10 years ago.Heijnen and van Dijken introduce the Gibbs' energy dissipation as a concept with favorable characteristics compared with various other approaches, including thermodynamic efficiency, as introduced by this author.In this communication, it will be shown that the “dissipation” and the “thermodynamic efficiency” description are completely equivalent and that there can be no preference for one of these in terms of rigor or characteristics. © 1993 John Wiley & Sons, Inc.
Response to comments on “in search of a thermodynamic description of biomass yields for the chemotropic growth of microorganisms”
Authors: Heijnen J. J. , van Dijken J. P. 
Published: December 2004

AbstractIt is shown that for the thermodynamic description of microbial growth there does not exist complete equivalency between the “efficiency” and “Gibbs energy dissipation” approach. The reasons for this absence of equivalency are discussed, and it is argued that the “dissipation approach” has much more favorable properties compared with the efficiency approach. © 1993 John Wiley & Sons, Inc.