bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic study of the lipase‐catalyzed synthesis of triolein
Authors: Lortie Robert , Trani Michael , Ergan Françoise 
Published: December 2004

AbstractThe kinetics of the synthesis of triolein catalyzed by immobilized Mucor miehei lipase were studied. Equilibrium constants for the synthesis of mono‐, di‐, and triolein were calculated from the equilibrium compositions for different initial ratios of glycerol and oleic acid by means of multiresponse regression. The 1,3‐specific lipase can catalyze the synthesis of triolein because the ester enzymatically formed with the primary alcohol isomerizes, through acyl migration, to an ester on the secondary hydroxyl. The freed primary hydroxyl may then undergo further enzymatic conversion. The rates of isomerization depend on the concentration of oleic acid. © 1993 Wiley & Sons, Inc.
Anaerobic waste‐activated sludge digestion–a bioconversion mechanism and kinetic model
Authors: Shimizu Tatsuo , Kudo Kenzo , Nasu Yoshikazu 
Published: December 2004

AbstractThe anaerobic bioconversion of raw and mechanically lysed waste‐activated sludge was kinetically investigated. The hydrolysis of the biopolymers, such as protein, which leaked out from the biological sludge with ultrasonic lysis, was a first‐order reaction in anaerobic digestion and the rate constant was much higher that the decay rate constant of the raw waste activated sludge. An anaerobic digestion model that is capable of evaluating the effect of the mechanical sludge lysis on digestive performance was developed. The present model includes four major biological processes–the release of intracellular matter with sludge lysis; hydrolysis of biopolymers to volatile acids; the degradation of various volatile acids to acetate; and the conversion of acetate and hydrogen to methane. Each process was assumed to follow first order kinetics. The model suggested that when the lysed waste‐activated sludge was fed, the overall digestive performance remarkably increased in the two‐phase system consisting of an acid forming process and a methanogenic process, which ensured the symbiotic growth of acetogenic and methanogenic bacteria. © 1993 Wiley & Sons, Inc.
Determination of kinetic parameters of fermentation processes by a continuous unsteady‐state method: Application to the alcoholic fermentation of D‐xylose by Pichia stipitis
Authors: Domínguez H. , Núñez M. N. , Chamy R. , Lema J. M. 
Published: December 2004

AbstractA quick technique for determination of kinetic parameters of fermentation processes is proposed and applied to the transformation of D‐xylose into ethanol by Pichia stipitis. The commonly used method to evaluate these parameters is based on achieving several steady states. In the proposed procedure, μm and Ks can be determined from only one steady state, by provoking a disturbance over it, after allowing the system to return to the original conditions. The main difference between the steady and unsteady state methods is the required fermentation time; while the former method lasted 350 h, the latter required a period 25 times lower. Kinetic and stoichiometric parameters were determined with both methods under anoxic and limited oxygen concentration conditions. Results from the two methods were compared, giving only 2% and 4.5% differences in the values of Ks and μm and a little over 4% for μm were the deviations under the latter ones. © 1993 Wiley & Sons, Inc.
Emulsion liquid membrane extraction of lactic acid from aqueous solutions and fermentation broth
Authors: Schöller C. , Chaudhuri J. B. , Pyle D. L. 
Published: December 2004

AbstractStudies on the batch extraction of lactic acid using an emulsion liquid membrane system are reported. The membrane phase consists of the tertiary amine carrier Alamine 336 and the surfactant Span 80 dissolved in n‐heptane/paraffin and aqueous solutions of sodium carbonate in the internal phase. The effects of internal phase reagent, extraction temperature, and initial external phase pH on the extraction efficiency and the emulsion swelling are examined. A statistical factorial experiment on extraction from clarified lactic acid fermentation broth was carried out to obtain knowledge of the performance of the extraction system from a broth. The extraction efficiency from the fermentation broth is found to be lower as compared to aqueous solutions of pure lactic acid. The effect of pH and the presence of other ionic species on selectivity are discussed. © 1993 John Wiley & Sons, Inc.
Overexpression of cloned genes using recombinant escherichia coli regulated by a T7 promoter: II. Two‐stage continuous cultures and model simulations
Authors: Miao Fudu , Kompala Dhinakar S. 
Published: December 2004

AbstractA two‐stage culture strategy was studied for continuous high‐level production of a foreign protein in the chemically inducible T7 expression system. The first stage is dedicated to the maintenance of plasmid‐bearing cells and the second stage to the target protein synthesis by induction of cells coming from the first stage. On entering the second stage, recombinant cells undergo a gradual induction of the target gene expression. These plasmid‐bearing cells experience dynamic changes in intracellular compositions and specific growth rates with their individual residence times. Therefore, the overall cultural characteristics in the production stage are really averages of the contributions from the various cells with different residence times. The behavior of the two‐stage culture is described by a model, which accounts for dynamic variations of cell growth and protein synthesis rates with cell residence times. Model simulations were compared with experimental results at a variety of operating conditions such as inducer concentration and dilution rate. This model is useful for understanding the behavior of two‐stage continuous cultures. © 1993 John Wiley & Sons, Inc.
Investigation of subpopulation heterogeneity and plasmid stability in recombinant escherichia coli via a simple segregated model
Authors: Bentley William E. , Quiroga Oscar E. 
Published: December 2004

AbstractMany microbial and cell cultures exhibit phenomena that can best be described using a segregated modeling approach. Heterogeneties are more marked in recombinant cell cultures because subpopulations, which often exhibit different growth and productivity characteristics, are more easily identified by selective markers. A simple segregated mathematical model that simulates the growth of recombinant Escherichia coli cells is developed. Subpopulations of different growth rate, plasmid replication rate, and plasmid segregation probability are explicitly considered. Results indicate that a third mechanism of plasmid instability, referred to here as a “downward selective pressure,” is significant when describing plasmid loss in batch and chemostat cultures. Also, the model agrees well with experimental data from cultures under antibiotic selective pressure. Finally, model simulations of chemostat cultures reveal the importance of initial conditions on culture stability and the possible presence of nonrandom partitioning functions. © 1993 John Wiley & Sons, Inc.
A two‐stage bioreactor system for the production of recombinant proteins using a genetically engineered baculovirus/insect cell system
Authors: Zhang Junli , Kalogerakis Nicolas , Behie Leo A. , Iatrou Kostas 
Published: December 2004

AbstractA two‐stage bioreactor scheme was developed for the large‐scale production of recombinant proteins using a genetically engineered baculovirus/insect cell system. The first bioreactor was employed for cell growth and the second for cell infection. Silkworm Bm5 cells were infected with a recombinant baculovirus, BmNPV/P5.cat, containing a bacterial chloramphenicol acetyltransferase (CAT) gene under the control of the polyhedrin gene promoter of Bombyx mori nuclear polyhedrosis virus (BmNPV). This recombinant baculovirus has been used as an expression vector for the production of recombinant CAT enzyme. A specific productivity of 82 to 90 μg CAT/(106 cells) was obtained using the BmNPV/Bm5 expression system, a yield similar to that achieved using the AcNPV/Sf expression system. Repeated infection of high‐density cell cultures did not reduce the specific productivity of the CAT enzyme. Most importantly, the problems associated with the infection of high‐density cell cultures were resolved by means of controlled infection conditions and appropriate replenishment of spent culture medium following infection. The glucose uptake rate by the cells following infection was 50% higher than that by the cells before infection. Not only did the infection of high‐density cell cultures result in consistent yields of 250 mg/L of CAT enzyme, but also the two‐stage bioreactor system was proven to be reliable for a long‐term operation beyond 600 h. © 1993 John Wiley & Sons, Inc.
Enhanced recovery of solavetivone from Agrobacterium transformed root cultures of Hyoscyamus muticus using integrated product extraction
Authors: Corry James P. , Reed William L. , Curtis Wayne R. 
Published: December 2004

AbstractThe integrated recovery of solavetivone from fungus elicited “hairy root” cultures of Hyoscyamus muticus is examined using volatile organic solvents and solid‐phase adsorbents in an external loop extraction configuration. Hexane and pentane are shown to be toxic when added directly to the culture; however, growth of roots is not inhibited when cultures are exposed to media saturated with these hydrocarbons. Solid‐phase neutral adsorbents, XAD‐7 and XAD‐16, display higher capacity and better solavetivone partitioning capability than the hydrocarbons; however, their selectivity for the sesquiterpene solavetivone is poor in comparison with hexane. In both cases, the integration of product recovery through extraction resulted in a doubling of product formation by alleviating feedback repression. Implications of these results to the recovery of secondary metabolites from plant root cultures are discussed. © 1993 John Wiley & Sons, Inc.
Electric prompting and control of denitrification
Authors: Sakakibara Yutaka , Kuroda Masao 
Published: December 2004

AbstractThe effectiveness of a denitrification process which is driven and controlled by an electric current is demonstrated. Denitrifying microorganisms were immobilized on a carbon electrode and hydrogen was produced through the electrolysis of water. The hydrogen was utilized for the reduction of nitrate to N2. The denitrification rate was a linear function of the electric current, and it was shown that about 1 mol of electron reduces 0.2 mol of nitrate to N2 gas. These results exhibit that the proposed process is simple and feasible, especially for the treatment of low‐strength nitrate solutions. © 1993 John Wiley & Sons, Inc.
Gas phase acetaldehyde production in a continuous bioreactor
Authors: Hwang Soon Ook , Trantolo Debra J. , Wise Donald L. 
Published: December 2004

AbstractThe gas phase continuous production of acetaldehyde was studied with particular emphasis on the development of biocatalyst (alcohol oxidase on solid phase support materials) for a fixed bed reactor. Based on the experimental results in a batch bioreactor, the biocatalysts were prepared by immobilization of alcohol oxidase on Amberlite IRA‐400, packed into a column, and the continuous acetaldehyde production in the gas phase by alcohol oxidase was performed. The effects of the reaction temperature, flow rates of gaseous stream, and ethanol vapor concentration on the performance of the continuous bioreactor were investigated. © 1993 John Wiley & Sons, Inc.
Modeling lipolysis in a reversed micellar system: Part II—membrane reactor
Authors: Prazeres D. M. F. , Lemos F. , Garcia F. A. P. , Cabral J. M. S. 
Published: December 2004

AbstractOlive oil hydrolysis using Chromobacterium viscosum lipase B in a reversed micellar media was investigated in a membrane reactor. The dynamic evolution of the product concentration both in the concentrate and permeate stream was analyzed using a mechanistic model previously developed by us and further modified in this work. A kinetic law with a second‐order dependence in the substrate concentration and nonlinear product inhibition was found to be the most adequate for the description of the hydrolysis data over an extensive range of time and substrate concentration. These findings are discussed in terms of the specific interactions occurring in the membrane reactor. © 1993 John Wiley & Sons, Inc.
Affinity‐based reversed micellar protein extraction: II. Effect of cosurfactant tail length
Authors: Kelley Brian D. , Wang Daniel I. C. , Hatton T. Alan 
Published: December 2004

AbstractThe selectivity of protein extraction by reversed micellar solutions can be improved by the addition of affinity cosurfactants bearing ligands which bind strongly to the target protein. The interactions between cosurfactant and protein, as well as the interfacial activity of both the free cosurfactant and the protein–cosurfactant complex, were accounted for in a model of the affinity‐partitioning process. The aqueous phase dissociation constant was used to describe the protein–ligand interactions. The interfacial partition coefficient for several cosurfactant families varied with tail length according to the well‐established hydrophobic effect. Control studies with alkylated chymotrypsin showed that when longer hydrophobic tails are irreversibly attached to the protein, the protein partitions more strongly to the reversed micellar phase. In contrast, for reversible protein–cosurfactant binding, the model predicts a maximum in protein uptake when the cosurfactant tail length is varied; the decrease at longer tail lengths is due to the lowered aqueous phase concentration of affinity cosurfactant, resulting in the formation of fewer protein–cosurfactant complexes. This behavior was confirmed experimentally. © 1993 John Wiley & Sons, Inc.
Estimation of melting curves from enzymatic activity–temperature profiles
Authors: Hei Derek J. , Clark Douglas S. 
Published: December 2004

AbstractMeasuring the reversible thermal unfolding of enzymes is valuable for quantifying the effects of environmental factors on the thermodynamic stability of proteins. The thermal unfolding behavior of enzymes is typically studied using calorimetry or optical techniques such as circular dichroism, fluorescence, or light scattering. These techniques often have practical limitations and usually require the protein to be electrophoretically pure. An alternative technique for analyzing the thermodynamic stability of enzymes is to estimate the melting curve from temperature–activity data. This technique does not require electrophoretically pure enzyme, provided the sample does not have competing enzymatic activities or proteins which can affect enzyme stability (e.g., proteases). Moreover, small amounts of contaminant proteins should not affect the results as long as enzymatic assays are performed at low protein concentrations where nonspecific protein–protein interactions are negligible. To illustrate this technique, the melting curve for β‐galactosidase from Escherichia coli in the presence of 1 mM EDTA, and the shift caused by adding 1 mM Mg+2, were calculated from activity–temperature data. Melting temperatures predicted from activity–temperature data compared closely with those obtained using other techniques. Application of this analysis to multisubstrate enzymes is illustrated by estimating the melting profiles for partially purified hydrogenases from several thermophilic Methanococcii. Limitations and important considerations for estimating melting profiles from activity–temperature data are discussed. © 1993 John Wiley & Sons, Inc.
Scaleup of spinfilter perfusion bioreactor for mammalian cell retention
Authors: Yabannavar V. M. , Singh V. , Connelly N. V. 
Published: December 2004

AbstractA spinning cylindrical filter, known as a spinfilter, permits the mammalian cell bioreactor operation at high perfusion rates leading to very high cell densities (107 mL−1). Filter screens with openings (25 μm) slightly larger than the average cell size have been used to retain single cells in suspension over a long period of operation without clogging. We have previously shown why it is necessary to optimize the rotational speed of the spinfilter in order to achieve efficient cell retention and avoid potential screen clogging. Effects of bulk mixing and perfusion rate on screen fouling and cell retention were also investigated. Based on this analysis, in this article, we suggest strategies for scaleup of spinfilters. Experimental data from 12‐ and 175‐L (working volume) bioreactors is shown in support of the scaleup analysis. © 1994 John Wiley & Sons, Inc.
A new visualization chamber to study the transient volumetric response of yeast cells submitted to osmotic shifts
Authors: Berner J.‐L. , Gervais P. 
Published: December 2004

AbstractA visualization chamber has been developed to analyze potential correlations between osmotic step increase on yeasts and the resultant cell volume decreases. Image analysis was used to characterize the step increases in the center of the chamber and to measure the changes in the cell volume. Step increases of different intensities have been performed on the yeast Saccharomyces cerevisiae. This device has allowed the kinetics of the volumetric evolution of the cells to be observed. The water exit flow rate from the cell was found to occur in the first 10 s following the hypertonic step change. Comparison of the time constants of the chamber and of the cell volume variations allowed to conclude that the time constant of the water transfer across the membrane was short (about 1 s). © 1994 John Wiley & Sons, Inc.
A prototype neural network supervised control system for Bacillus thuringiensis fermentations
Authors: Zhang Qin , Reid John F. , Bruce Litchfield J. , Ren Jinliang , Chang Shiuan‐Wu 
Published: December 2004

AbstractThis article discusses the development of a prototype neural network‐based supervisory control system for Bacillus thuringiensis fermentations. The input pattern to the neural network included the type of inoculum, operation temperature, pH value, accumulated process time, optical density in fermentation medium, and change in optical density. The output from the neural network was the predicted optical density for the next sampling time. The control system has been implemented in both a computer simulation and a laboratory fermentation experiment with promising results. © 1994 John Wiley & Sons, Inc.
Ammonia affects the glycosylation patterns of recombinant mouse placental lactogen‐I by chinese hamster ovary cells in a pH‐dependent manner
Authors: Borys Michael C. , Linzer Daniel I. H. , Papoutsakis Eleftherios T. 
Published: December 2004

AbstractThe N‐linked glycosylation of the recombinant protein mouse placental lactogen‐I (mPL‐I) expressed by Chinese hamster ovary (CHO) cells under nongrowth conditions was inhibited by increasing levels of ammonium chloride (3 and 9 mM) in a serum‐free, protein expression medium. The effect of ammonia on glycosylation was dependent on the extracellular pH (pHe). In media containing 0 and 9 mM ammonium chloride, the percentage of the most heavily glycosylated forms of secreted mPL‐I decreased from ca. 90% to ca. 25% at pHe 8.0, and from ca. 90% to ca. 65% at pHe 7.6, respectively. However, at pHe 7.2, the most heavily glycosylated forms of secreted mPL‐I decreased from ca. 90% to ca. 80% in media containing 0 and 9 mM ammonium chloride, respectively. Inhibition of mPL‐I glycosylation was found to correlate with the calculated concentrations of the ammonia species (NH3). Control experiments showed that the ammonia effect on mPL‐I glycosylation could not be attributed to increased chloride concentration or osmolarity, or to extracellular events after secretion of the recombinant protein into the supernatant. Ammonium chloride, 9 mM, inhibited the expression rate of MPL‐I by CHO cells at low pHe. © 1994 John Wiley & Sons, Inc.
Microencapsulated human bone marrow cultures: A potential culture system for the clonal outgrowth of hematopoietic progenitor cells
Authors: Levee Minette G. , Lee Gyun‐Min , Paek Se‐Hwan , Palsson Bernhard O. 
Published: December 2004

AbstractCurrently the most successful methods for culturing human hematopoietic cells employ some form of perfused bioreactor system. However, these systems do not permit the clonal outgrowth of single progenitor cells. Therefore, we have investigated the use of alginate–poly‐L‐lysine microencapsulation of human bone marrow, combined with rapid medium exchange, as a system that may overcome this limitation for the purpose of studying the kinetics of progenitor cell growth. We report that a 12 to 24‐fold multilineage expansion of adult human bone marow cells was achieved in about 16 to 19 days with this system and that visually identifiable colonies within the capsules were responsible for the increase in cell number. The colonies that represented the majority of cell growth originated from cells that appeared to be present in a frequency of about 1 in 4000 in the encapsulated cell population. These colonies were predominantly granulocytic and contained greater than 40,000 cells each. Large erythroid colonies were also present in the capsules, and they often contained over 10,000 cells each. Time profiles of the erythroid progenitor cell density over time were obtained. Burst‐forming units erythroid (BFU‐E) peaked around day 5, and the number of morphologically identifiable erythroid cells (erythroblasts through reticulocytes) peaked on day 12. We also report the existence of a critical inoculum density and how growth was improved with the use of conditioned medium derived from a microcapsule culture initiated above the critical inoculum density. Taken together, these results suggest that microencapsulation of human hematopoietic cells allows for outgrowth of progenitor, and possible preprogenitor, cells and could serve as a novel culture system for monitoring the growth and differentiation kinetics of these cells.
Biosorption of lead and nickel by biomass of marine algae
Authors: Holan Z. R. , Volesky B. 
Published: December 2004

AbstractScreening tests of different marine algae biomas types revealed a high passive biosorptive uptake of lead up to 270 mg Pb/g of biomass in some brown marine algae. Members of the order Fucales perfomed particularly well in this descending sequence: Fucus > Ascophyllum > Sargassum. Although decreasing the swelling of wetted biomass particles, their reinforcement by crosslinking may significantly affect the biosorption performance. Lead uptakes up to 370 mg Pb/g were observed in crosslinked Fucus vesiculosus and Ascophyllum nodosum. At low equilibrium residual concentrations of lead in solution, however, ion exchange resin Amberlite IR‐120 had a higher lead uptake than the biosorbent materials. An order‐of‐magnitude lower uptake of nickel was observed in all of the sorbent materials examined. © 1994 John Wiley & Sons, Inc.