bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physiological effects of TGFα‐PE40 expression in recombinant Escherichia coli JM109
Authors: George H. A. , Powell A. L. , Dahlgren M. E. , Herber W. K. , Maigetter R. Z. , Burgess B. W. , Stirdivant S. M. , Greasham R. L. 
Published: December 2004

AbstractPhysiological effects of isopropyl‐thiogalactopyranoside (IPTG) induction were examined in Escherichia coli strain JM109 expressing a fusion protein composed of transforming growth factor alpha and a 40‐kD portion of Pseudomonas aeruginosa exotoxin A (TGFα‐PE40) under control of the tac promoter. Fermentations at the 15‐L scale in complex medium compared growth and metabolite profiles of the untransformed JM109 host strain, the strain transformed with the vector lacking the TGFα‐PE40 open reading frame (JM109[pKK2.7]), and the strain with the complete plasmid for TGFα‐PE40 expression (JM109[pTAC‐TGF57‐PE40]). Metabolite and growth profiles of JM109 (pTAC‐TGF57‐PE40) cultures changed significantly in IPTG‐induced versus uninduced cultures. Prior to induction, glucose was metabolized to acetate or completely oxidized to CO2. Following induction, pyruvate was also excreted in addition to acetate. In the absence of inducer, pyruvate was excreted by JM109 (pTAC‐TGF57‐PE40) only when dissolved oxygen levels fell to less than 10% of saturation (microaerobic rather than anaerobic conditions). The untransformed JM109 host strain or JM109 (pKK2.7) did not excrete pyruvate in the presence or absence of inducer, although JM109 (pKK2.7) exhibited a pattern of growth following addition of IPTG that closely resembled JM109 (pTAC‐TFG57‐PE40). Fermentations of JM109 (pTAC‐TFG57‐PE40) in a synthetic medium supported lower expression levels, but resulted in similar alterations in metabolite profiles. Induction in synthetic medium resulted in pyruvate excretion without further acetate accumulation. Taken together, these data suggest that one consequence of TGFα‐PE40 expression in JM109 is altered patterns of pyruvate oxidation. © 1992 John Wiley & Sons, Inc.
Separation of fructose and glucose mixture by zeolite Y
Authors: Cheng Y. L. , Lee T. Y. 
Published: December 2004

AbstractNa−, K−, Ba−, and Ca−Y were employed for the separation of fructose and glucose in an adsorption column. Effects of temperature, solvent flow rate, amount of mixture injection, and exchangeable cations on the separation were investigated. Efficiency of separation was used as a criterion to characterize the effectiveness of the separation. The transport and kinetic parameters for the column separation were also presented. From simple pulse experiments and moment analysis, the obtained process information of equilibrium and dynamic parameters might be used to design, operate, and control the separation column. © 1992 John Wiley & Sons, Inc.
Analysis of productivity in lysis‐deficient lambda expression systems
Authors: Padukone N. , Peretti S. W. , Ollis D. F. 
Published: December 2004

AbstractThe integrated state of λ in the host chromosome in lysogeny can be combined with its extrachromosomal replication in the lytic state to achieve high cloned gene productivities. Our previous studies on λ expression systems21,22 have shown 100% segregational stability of the cloned gene in lysogeny and cloned gene product levels up to 15% of total cell protein in a mutant lytic state. However, the expression phase of systems based on Escherichia coli JM109 and JM105 showed partial lysis of the productive culture despite a mutation in the lysis gene S of the lambda vector resulting in extracellular release of the cloned gene product. In the current study, we have eliminated partial lysis in the expression phase of λ systems and conducted a detailed comparative analysis of these systems in relation to maximization of cloned gene productivity. The elimination of partial cell lysis by using a nonpermissive strain Y1089 did not enhance product yields vs. earlier systems that exhibited partial lysis. The elimination of nonessential λ protein production by construction of a new vector NP326 did not yield higher product yields presumably because of the small fraction of these proteins in the lytic state. Temperature induction of the lysogen Y1089(NM1070) resulted in higher product levels than direct infection of Y1089 by the phage vector at a high multiplicity. Using infection experiments, we found the promoter lacUV5 in the vector λZEQS to yield threefold higher product levels than lac in NM1070, suggesting possible further enhancement of productivity with stronger promoters. The occurrence or absence of partial lysis in λ systems could be used beneficially to achieve extracellular or intracellular product as desired. The large capacity of λ vectors for insert DNA suggests potential applications in obtaining highly amplified levels of operons and multienzyme systems. © 1992 John Wiley & Sons, Inc.
Ethanol production from eucalyptus wood hemicellulose hydrolysate by Pichia stipitis
Authors: Ferrari M. D. , Neirotti E. , Albornoz C. , Saucedo E. 
Published: December 2004

AbstractEthanol production was evaluated from eucalyptus wood hemicellulose acid hydrolysate using Pichia stipitis NRRL Y‐7124. An initial lag phase characterized by flocculation and viability loss of the yeast inoculated was observed. Subsequently, cell regrowth occurred with sequential consumption of sugars and production of ethanol. Polyol formation was detected. Acetic acid present in the hydrolysate was an important inhibitor of the fermentation, reducing the rate and the yield. Its toxic effect was due essentially to its undissociated form. The fermentation was more effective at an oxygen transfer rate between 1.2 and 2.4 mmol/L h and an initial pH of 6.5. The hydrolysate used in the experiences had the following composition (expressed in grams per liter): xylose 30, arabinose 2.8, glucose 1.5, galactose 3.7, mannose 1.0, cellobiose 0.5, acetic acid 10, glucuronic acid 1.5, and galacturonic acid 1.0. The best values obtained were maximum ethanol concentration 12.6 g/L, fermentation time 75 h, fermentable sugar consumption 99% ethanol yield 0.35 g/g sugars consumed, and volumetric ethanol productivity 4 g/L day. © 1992 John Wiley & Sons, Inc.
Cellulase activity in commercial lipase preparations
Authors: Derksen Johannes T. P. , Boswinkel Gerard , Cuperus F. Petrus 
Published: December 2004

AbstractPolymeric membranes are increasingly used as supports for the immobilization of enzymes in bioreactors. One of the more common reactor types employed in lipase‐catalyzed hydrolysis of oils, contains modified cellulose as a membrane material. We found that this type of material is readily attacked by cellulase present in several commercially available lipase preparations. This leads to membrane damage, reactor instability, and leakage. We conclude that cellulose membranes are not suitable as supports in bioreactors for the immobilizartion of these lipases. The development of alternative membranes is currently in progress. © 1992 John Wiley & Sons, Inc.
Intracellular ribonucleotide pools as a tool for monitoring the physiological state of in vitro cultivated mammalian cells during production processes
Authors: Ryll Thomas , Wagner Roland 
Published: December 2004

AbstractIntracellular analysis has been shown to be useful as a tool for control production processes based on in vitro cultivated hybridoma and recombinant animal cells. Nucleotides were found to present the best target as they reflect the exact physiological state of a culture. Following the progress of batch, perfused, and chemostat cultures cell specific regularities were found in various biochemical correlations which allowed the generation of three characteristic parameters based on the interaction of particular nucleotides: the nucleotide triphosphate (NTP) ratio ([ATP + GTP]/[UTP + CTP]), the uridine (U) ratio (UTP/UDP–GNAc), and the combined ratio NTP/U ([UDP–GNAc (ATP + GTP)/ UTP (UTP + CTP)]). These allowed a direct description of the growth cycle by means of specific values or behavior for every phase of the culture. In particular, the critical phase of entrance into the phase of reduced growth was predicted up to 24 h earlier than was possible with the classical method of microscopic cell control. A specific function for the application of in vitro cultivated processes is proposed with an NTP‐to‐U plot which combines the results obtained by the cell analysis and which offers a tool for the control and regulaiton of cell growth–derived procedures. © 1992 John Wiley & Sons, Inc.
The equilibrium and kinetics of N‐acetyl‐tryptophan phenylethyl ester synthesis by agarose–chymotrypsin in organic media
Authors: Blanco Rosa M. , Guisán José M. , Halling Peter J. 
Published: December 2004

AbstractThe synthesis of N‐acetyl tryptophan phenylethyl ester in organic media is catalyzed by suspended agarose beads with multipoint covalently attached chymotrypsin. A dilute aqueous phase is trapped within the gel beads and may be manipulated separately from the organic phase. The equilibrium position becomes more favorable as the solvent polarity decreases, with Keq increasing 38 times between 2‐butanone and 1,1,1‐trichloroethane. The more apolar solvents also give faster kinetics. Addition of cosolvents (up to 10% dimethylformamide or 20% acetonitrile) does not affect the rate but does substantially reduce the equilibrium yield, presumably also by making the organic phase more polar. With trichloroethane as solvent the enzyme appears to be kinetically saturated with 1M phenylethanol. Doubling this concentration also does not cause the expected increase in equilibrium conversion, probably again because Keq is reduced in the more polar organic phase. Increased temperature raises the reaction rate as expected but has little effect on the equilibrium. © 1992 John Wiley & Sons, Inc.
Influence of oxygen adsorption on the dynamic KLa measurement in three‐phase slurry reactors
Authors: Boon M. , Meeder T. A. , Heijnen J. J. , Luyben K. Ch. A. M. 
Published: December 2004

AbstractTo check for possible mass transfer limitations of oxygen and/or carbon dioxide in kinetic experiments on microbial desulphurization of coal, it is important to properly measure the volumetric mass transfer coefficient (kLa) especially at high slurry densities. Volumetric mass transfer coefficients of oxygen, at different solid hold‐up values (εs = 0 to 0.28) of coal slurries (dpar < 100 * 10−6 m), were measured in a lab scale fermentor and in a lab scale pachuca tank, using the dynamic gas–liquid absorption method. It was shown that serious errors could occur due to oxygen adsorption at the coal surface. Using the data of an independently measured adsorption isotherm, the real kLa could be calculated from the measured apparent kLa. The results show a kLa decrease of 40% to 50% at a volumetric solid hold‐up of 28%. Estimation of the oxygen and carbon dioxide transfer rates, from the measured mass transfer coefficients, indicates that the stirred fermentor is suitable for kinetic experiments at high slurry densities, whereas the pachuca tank and shake flask are not. © 1992 John Wiley & Sons, Inc.
Poly(ethylenimine)‐reinforced liquid‐core capsules for the cultivation of hybridoma cells
Authors: Hsu Yuan‐Lung , Chu I‐Ming 
Published: December 2004

AbstractThe mechanical stability of liquid‐core alginate‐poly‐L‐lysine (PLL) capsules used for encapsulation of hybridoma cells can be greatly enhanced by the inclusion of poly(ethylenimine) (PEI) in the hardening solution containing calcium chloride. The PEI can also reinforce the PLL‐coated carboxymethyl‐celluose liquid‐core capsules. The cultivation of murein hybridoma CT04 in these two capsules was carried out. Cell concentrations higher than 108 cells/mL per capsule were obtained with ca. 80% of the specific antibody productivity as the freely suspended cells. These capsules could withstand severe agitation and aeration in an air‐lift reactor over a period of 3 weeks with minimal damage. © 1992 John Wiley & Sons, Inc.
Effect of subunit dissociation, denaturation, aggregation, coagulation, and decomposition on enzyme inactivation kinetics: II. Biphasic and grace period behavior
Authors: Lencki Robert W. , Arul Joseph , Neufeld Ronald J. 
Published: December 2004

AbstractA model previously developed to characterize enzymatic in activation behavior was used to explain the non‐first‐order biphasic and grace period phenomena that are often observed with oligomeric enzymes. Luciferase and urease were used as model enzyme such as luciferase, the oligomer initially dissociates reversibly into two native monomer species. These native monomers can then reversibly denature and irreversibly aggregate and coagulate. With the hexamer, urease, two trimers are formed that can subsequently aggregate to form an inactive hexamer. The dissociated monomer species of luciferase do not possess catalytic activity, so the inactivation mechanism, is biphasic; the first slope of a first‐order kinetic plot is influenced by the reversible oligomer/monomer/denatured‐monomer transition. Whereas the second slope is associated with either irreversible aggregation or coagulation. In contrast, the trimer of urease has the same activity as the hexamer; therefore, during the intitial hexamer–trimer transition, little activity loss occurs. However, as the trimer concentration increases, activity decreases as a result of trimer aggregation. As a result, grace period inactivation behavior is observed. © 1992 John Wiley & Sons, Inc.
Effects of the kinetics of osmotic pressure variation on yeast viability
Authors: Gervais P. , Marechal P. A. , Molin P. 
Published: December 2004

AbstractThe variation rate of the osmotic pressure increase was found to have a great effect on the viability of yeasts subjected to hyperosmotic stress. A low intensity of the increase rate of osmotic pressure could maintain an important viability of the cells (about 90 to 100%) even for very high levels of osmotic pressure (about 108Pa). The viability level was found to be highly dependent on the physiological state of the cells: Variations in the properties of the cell membrane were supposed to be involved in such a dependence. © 1992 John Wiley & Sons, Inc.
Some observations on protease production in continuous suspension cultures of Bacillus firmus
Authors: Moon Seung‐Hyeon , Parulekar Satish J. 
Published: December 2004

AbstractInvariance of culture conditions in steady state continuous cultures make these a very valuable tool to study the influence of various culture parameters on cell growth and synthesis of primary and secondary metabolites. The result of a parametric study on production of protease in continuous suspension cultures of Bacillus firmus NRS 783 are reported in this article. This strain is a superior producer of an alkaline protease with major application in the detergent industry. The parameters investigated include dilution rate and concentrations of yeast extract, ammonium, and inorganic phosphate in the bioreactor feed, glucose being the principal carbon source in all experiments. The regulatory effects of the key culture parameters on cell growth, synthesis and secretion of protease, and production of acetic acid are investigated. The relations among the specific cell growth rate, specific utilization rates of the principal carbon, nitrogen, and phosphorous sources, and specific production rates of two nonbiomass products, viz., acetic acid and protease, are examined, and the effects of the manipulated culture parameters on these relations, specific protease activity, and yields of cell mass, protease, and acetic acid on the basis of the principal carbon, nitrogen, and phosphorous sources are studied. An increase in dilution rate led to increases in specific utilization rates of the principal carbon, nitrogen, and phosphorous sources and specific production rates of acetic acid and protease and decreases in bulk activities/concentrations of the three products (acetic acid, cell mass, and protease). As a result, the productivities of the three species were maximized at an intermediate dilution rate. Increased supply of yeast extract (a rich source of amino acids, proteins, and vitamins, besides being an additional source of carbon, nitrogen, and phosphorus) promoted cell mass formation but reduced protease production per unit cell mass. Increased supply of nitrogen and phosphorous sources stimulated protease synthesis up to certain threshold levels and repressed the enzyme synthesis beyond the threshold levels. With increased supply of the nitrogen source, the phosphorous source was more efficiently utilized for cell growth and protease synthesis. Stable maintenance of continuous cultures of B. firmus over prolonged period is demonstrated in this study. © 1993 John Wiley & Sons, Inc.
Effects of oxygen and ethanol on recombinant yeast fermentation for hepatitis B virus surface antigen production: Modeling and simulation studies
Authors: Shi Yuan , Ryu Dewey D. Y. , Yuan Wei‐Kang 
Published: December 2004

AbstractA model was formulated to examine the competitive growth of two phenotypes (Leu+ and Leu−) and the product formation with recombinant Saccharomyces cerevisiae strain DBY‐745, which contains the shuttle vector pYGH3‐16‐s with the foreign gene HBsAg (hepatitis B virus surface antigen) as well as experimental fedbatch fermentation data. The important state variables and the process parameters evaluated include (1) the ratio of the plasmid‐free cell concentration to the plasmid‐containing cell concentration (ρ = X−X+), (2) the expression of human hepatitis B surface antigen g (CH), (3) the glucose consumption (S), (4) the ethanol production (/), (5) the change of working volume (V) in the fermentor, (6) the different specific growth rates of two phenotype cells, and (7) the plasmid loss frequency coefficient (α ). These variables and other parameters were carefully defined, their correlations were studied, and a mathematical model using a set of nonlinear ordinary differential equations (ODEs) for fed‐batch fermentation was then obtained based on the theoretical considerations and the experimental results. The extended Kalman filter (EKF) methods was applied for the best estimate of these variables based on the experimentally observable variables: ρV, and g (CH). Each of these variable was affected by random measuring errors under the different operating conditions. Simulation results presented for verification of the model agreed with our observations and provided useful information relevant to the operation and the control of the fedbatch recombinant yeast fermentation. The method of predicting an optimal profile of the cell growth was also demonstrated under the different dissolved oxygen concentrations. © 1993 John Wiley & Sons, Inc.
Development of bacterial cytochrome P‐450cam (Cytochrome m) production
Authors: Horowitz Jeffrey B. , Vilker Vincent L. 
Published: December 2004

AbstractCytochrome P‐450cam monooxygenase is an important bacterial redox enzyme system with potential commercial value for detoxifying trace hydrocarbon contaminants, catalyzing regiospecific hydroxylations, and amperometric biosensing. The present study was undertaken to increase productivity of this enzyme, which is induced in its host, pseudomonas putida PpG 786, by D(+)‐camphor. Culture processes were studied in batch, fed‐batch, and continuous modes to evaluate metabolic behavior and develop constitutive equations for specific rate of growth (μ), camphor utilization (qp). Fed‐batch culture was characterized by an extended linear growth phase which is often encountered in hydrocarbon fermentations. Inhibition by the camphor solvent, dimethylformamide, was assessed. Production of the terminal protein of the p‐450cam enzyme system, cytochrome m, was shown to depend on growth medium iron content in fed‐batch culture and was increased by 130% over previously protocols by eliminating iron deficiency. A continuous process that enables greater production rates was developed by using oxygen enrichment while simultaneously reducing gas throughput. Camphor and oxygen requirements were determined for fedbatch and continuous growth. © 1993 John Wiley & Sons, Inc.
Complete design analysis of a continuous sterilizer for fermentation media containing suspended solids
Authors: Armenante Piero M. , Shen Li Yuan 
Published: December 2004

AbstractAn improved mathematical model was developed to design a continuous sterilizer for liquid fermentation media containing suspended solids. Unsteady‐state energy balances were used to determine the temperature distribution in the liquid medium and in the solid particles as a function of time and position within the particle, as the medium flows through the sterilizer. Such temperature profiles were used to determine the level of microbial reduction achieved by each component of the sterilizer and by the entire sterilization process. A considerable difference exists between the temperature in the particle core and in the surrounding liquid. This has a significant impact on the degree of sterility achieved by the process. The level of microbial reduction in the particles was found to be tens and or even hundreds of order of magnitude lower than the corresponding level achieved in the liquid. The role of the particle material on the degree of sterilization was also investigated. Solid materials typically found in fermentation media, such as wood or flour clumps were found to offer considerable resistance to the sterilization of the organisms lodged inside them. © 1993 Wiley & Sons, Inc.
Simultaneous enzymatic/electrochemical determination of glucose and L‐glutamine in hybridoma media by flow‐injection analysis.
Authors: Meyerhoff Mark E. , Trojanowicz Marek , Palsson Bernhard O. 
Published: December 2004

AbstractA split‐stream flow‐injection analysis system is described for simultaneous determination of glucose and L‐glutamine in serum‐free hybridoma bioprocesses media. Amperometric measurement of glucose is based on anodic oxidation of hydrogen peroxide produced by immobilized glucose oxidase within a triple layer membrane of an integrated flow‐through glucose‐selective biosensor. Determination of L‐glutamine is based on quantitating ammonium ions produced in a flow‐through enzymes reactor containing immobilized glutaminase enzyme, and subsequent downstream potentiometric detection of these ions by a nonacting‐based ion‐selective polymer membrane electrode. Endogenous potassium and ammonium ion interference in the L‐glutamine determination are eliminated by using a novel in‐line tubular cation‐exchange membrane unit to exchange these interferent species for cations undetectable by the membrane electrode. The first generation split‐steam flow‐injections system can assay 12 samples/h using direct injections of 50 μL of media samples, with linear responses to glucose in the range of 0.03 to 30mM, and log‐linear response to L‐glutamine from 0.1 to 10 mM. © 1993 Wiley & Sons, Inc.