bluuebunny/crossref_metadata_2025_split huggingface dataset:
A method for simultaneous determination of solubility and transfer coefficient of oxygen in aqueous media using off‐gas mass spectrometry
Authors: Dorresteijn R. C. , de Gooijer C. D. , Tramper J. , Beuvery E. C. 
Published: December 2004

AbstractA static method was developed that simultaneously determined the solubility of oxygen and the oxygen‐transfer coefficient in a stirred bioreactor. It was based on the static method developed by van Sonsbeek et al. to determine the ka in a liquid‐impelled loop reactor. Only physical properties of the liquid were used to determine both parameters using a mass spectrometer. Data about the solubility of oxygen in water are available from the literature. Therefore, the solubility of oxygen in water was used to compare our data with published data. Furthermore, the solubility of oxygen in trypticase soy broth was compared to literature data. No significant deviations between our data and literature data could be observed. Our static method and the commonly applied dynamic method to determine the oxygen‐transfer coefficient yielded similar results. The effect of temperature on the oxygen‐transfer coefficient could be expressed as the activation energy needed for the transition of oxygen from the gas to the water phase. This was verified using the Arrhenius equation. © 1994 John Wiley & Sons, Inc.
High pressure EPR studies of protein mobility in reversed micelles
Authors: Affleck Rhett , Clark Douglas S. , Kamat Sanjay , Russell Alan J. 
Published: December 2004

AbstractWe have investigated the effect of pressure on structural properties of subtilisin solubilized in reversed micelles of Tween‐85/isopropanol in hexane. Electron paramagnetic resonance (EPR) spectra of spin‐labeled enzyme indicate a reduction in spin‐label mobility when the enzyme is transferred from aqueous solution to the microemulsion. One explanation for the spectral broadening is a change in the protein's active‐site conformation and/or dynamics. However, over a W0 range of 80 to 180, EPR spectroscopy could detect no change in the enzyme's environment, conformation, or molecular dynamics. The EPR spectra also contained a contribution from free spin label located in an environment with a polarity roughly between that of propanol and bulk water. No changes in the polarity surrounding the free spin label nor in the enzyme's structural properties were evident at pressures up to 10,000 psi. Previous work has demonstrated that pressure can be used to manipulate the size of some reversed micelles, and the EPR data indicated that for this system such pressure tuning of micellar properties will not adversely affect the structure of solubilized enzyme. © 1994 John Wiley & Sons, Inc.
Structured model of genetic control via the lac promoter in Escherichia coli
Authors: Laffend L. , Shuler M. L. 
Published: December 2004

AbstractA model that describes induction of protein synthesis from lac‐based promoters has been developed and incorporated into the single‐cell model of Escherichia coli with transcriptional and translational modifications. Unlike previous models of lac‐based promoters, this model allows a priori prediction of the intracellular parameters controlling transcription from lac‐based promoters with only the extracellular levels of substrate and inducer as inputs. Because of the structural detail of the model, it is possible to simulate different genetic constructions for comparison, such as Laclq strains versus wild‐type cells, or including lacl on a multicopy plasmid. Expression from lac to tac promoters is predicted to yield 5% and 30% of the total cellular protein, respectively, with a pBR322‐type plasmid. The model predicts the experimental observation that the Laclq strain is not as fully induced as the wild‐type strains, even at higher inducer concentrations. Additionally, the model predicts the right order of magnitude of protein production from lac and tac promoters when mechanisms for attenuation of transcription at lower translational efficiency are considered. Finally, the model predicts that for high copy number systems ribosomes become limiting in the synthesis of plasmid‐encoded proteins. © 1994 John Wiley & Sons, Inc.
Continuous reaction‐separation process for enzymatic esterification in supercritical carbon dioxide
Authors: Marty Alain , Combes Didier , Condoret Jean‐Stéaphane 
Published: December 2004

AbstractThe study of enzymatic esterification by an immobilized lipase in supercritical carbon dioxide (SCCO2) and in n‐hexane, described in our previous works, was extended to continuous operation in a tubular fixed bed. The modeling of the reaction vessel operation was achieved through the use of the simple plug flow model coupled with the appropriate kinetic equation. Comparison with experiments proved to be satisfactory. The study of the postreactional separation, an important feature when using SCCO2, was undertaken experimentally and good selectivities and product recovery were obtained. © 1994 John Wiley & Sons, Inc.
Kinetics of leucrose formation from sucrose by dextransucrase
Authors: Böker Mathias , Jördening Hans‐Joachim , Buchholz Klaus 
Published: December 2004

AbstractLeucrose formation from sucrose and fructose by dextransucrase is of practical interest. It has been investigated at different experimental conditions, including the influence of temperature on reaction rate and selectivity. Under appropriate conditions high product yield can be obtained. Furthermore, a model is presented that allows interpretation of the experimental data.
Extraction of rIL‐2 inclusion bodies from Escherichia coli using cross‐flow filtration
Authors: Meagher M. M. , Barlett R. T. , Rai V. R. , Khan F. R. 
Published: December 2004

AbstractA cross‐flow membrane filtration process was developed for the recovery of rIL‐2 inclusion bodies from homogenized Escherichia coli. The membrane extraction process was comprised of a two‐step diafiltration followed by an extraction with 7 M GuHCl and a 40–fold dilution of the solubilized inclusion bodies into 0.01 M Tris–HCl, 0.035 M NaCl, pH 7.9. The first diafiltration was with a 0.03 M Tris–HCl, 5 mM ethylenediaminetetraacetic acid (EDTA), pH 8, followed by a diafiltration with 1.75 M GuHCl. All of the insoluble rIL‐2 was retained behind the membrane, whereas a GuHCl wash solubilized approximately 15% of the rIL‐2. The membrane process increased the yield of rIL‐2 in the diluted extract by threefold as compared to a similar centrifuge process with a significant increase in purity as determined by reverse‐phase high‐performance liquid chromatography (HPLC). © 1994 John Wiley & Sons, Inc.
Adsorption of BSA on strongly basic chitosan: Equilibria
Authors: Yoshida Hiroyuki , Nishihara Hideki , Kataoka Takeshi 
Published: December 2004

AbstractEquilibrium isotherms for adsorption of bovine serum albumin (BSA) on a new adsorbent, a strongly basic crosslinked chitosan (Chitopearl 2503), which is hard and is not compressed by pressure in a column, have been presented and compared with diethylaminoethyl (DEAE) Sepharose Fast Flow (hard gel). In Chitopearl 2503, when only buffer existed in the BSA solution, the isotherm was not affected by the initial concentration of BSA but it was affected by pH considerably. The isotherm was favorable when pH ≥ pl (≅ 4.8). When NaCl existed in the BSA solution, the amount of BSA absorbed on the resin decreased with increasing concentration of NaCl. When the concentration of NaCl was 200 mol/m3, the resin did not adsorb BSA at all. The equilibrium data were correlated by the Langmuir equation reasonably well. The BSA may be adsorbed mainly by electrostatic attraction between negatively charged BSA and positively charged quanternary ammonium groups at pH > pl and by protonation reaction of the primary ammonium groups by weak acid groups of BSA at pH = pl. These are confirmed by measuring the amount of inorganic ion exchanged for BSA. In DEAE Sepharose Fast Flow, the isotherm was favorable when pH > pl but unfavorable ar pH = pl. The saturation capacity of BSA on Chitopearl 2503 is about 1.3 to 2.2 times larger than that on DEAE Sepharose Fast Flow. © 1994 John Wiley & Sons, Inc.
Synthesis of dipeptide precursors with an immobilized thermolysin in ethyl acetate
Authors: Nagayasu Takeshi , Miyanaga Masamitsu , Tanaka Takaaki , Sakiyama Takaharu , Nakanishi Kazuhiro 
Published: December 2004

AbstractN‐(Benzyloxycarbonyl)‐L‐aspartyl‐L‐phenylalanine methyl ester (Z‐AspPheOMe), a precursor of the aspartame, and N‐(benzyloxycarbonyl)‐L‐phenylalanyl‐Lphenylalanine methyl ester (Z‐PhePheOMe) were synthesized from the respective amino acid derivatives with an immobilized thermolysin (EC 3.4.24.4) in ethyl acetate. Various factors affecting the synthesis of these dipeptide precursors were clarified. The initial synthetic rate was the highest at the water content of 3.5% for both reactions. The substrate concentration dependencies of the initial synthetic rate of Z‐AspkPheOMe and Z‐PhePheOMe with the immobilized enzyme in ethyl acetate were different from those in an aqueous buffer solution saturated with ethyl acetate but similar to those in the aqueous/organic biphasic system using the free enzyme. Particularly, the initial synthetic rate of Z‐AspPhOMe increased in order higher than first order with respect to the concentration of L‐phenylalanine methyl ester (PheOMe), whereas it decreased sharply with the concentration of N‐(benzyloxycarbonyl)‐L‐aspartic acid (Z‐Asp). Such kinetic behavior could be explained by regarding the inside of the immobilized enzyme as being a biphasic mode composed from the organic phase and aqueous phase where the enzymatic reaction takes place. The reaction in the aqueous/organic biphasic system using the free enzyme could be simulated by taking into consideration the partition of the substrate and the initial rate of synthesis in the aqueous buffer saturated with ethyl acetate. Based on this analysis, the rate of reaction with the immobilized enzyme in ethyl acetate could also be predicted. Z‐AsPheOMe and Z‐PhePheOMe were synthesized by the fed‐batch method where the acid component of the substrate was intermittently added during the course of reaction and by the batch method. In the synthesis of Z‐AspPheOMe, the synthetic rate and maximum yield of reaction as well as the stability of the immobilized enzyme were higher in the fed‐batch reaction than those in the batch reaction. In the synthesis of Z‐PhePheOMe, the results obtained by both methods were similar. © 1994 John Wiley & Sons, Inc.
Glycolipid membrane anchored recombinant protein production from CHO cells cultGred on porous microcarriers
Authors: Kennard M. L. , Piret J. M. 
Published: December 2004

AbstractRecombinant proteins were harvested from Chinese hamster ovary (CHO) cells by a controlled release process, which increased the purity and concentration of the harvested protein. Recombinant human melano‐transferrin (p97) was expressed linked to the outer surface of CHO cells by a glycosyl‐phosphatidylinositol (GPI) membrane anchor. Cells were grown to confluence in T‐flask culture, and the p97 harvested by replacing the growth medium for 30 min with phosphate‐buffered saline (PBS) containing 10 mU/mL phosphatidylinositol‐phospholipase C (PI‐PLC). The GPI anchor was selectively cleaved by PI‐PLC. In fresh medium, the CHO cells regained over 95% of their p97 expression within 40 h. The process was repeated for eight harvests. Harvested protein concentrations varied from 1.5 to 3.8 μg/mL due to difficulties in maintaining stable confluent T‐flask cultures. Harvesting from cells growing on porous microcarriers was investigated to increase p97 product concentrations and to overcome culture stability problems. Semicontinuous cultures were maintained in spinners for up to 76 days with average bioreactor cell densities of over 107 cell/mL. The p97 was harvested at up to 100 μg/mL and 30% purity with protein production remaining stable for 4 harvest cycles. Production of high levels of p97 from CHO cells was maintained at 0.5% serum. © 1994 John Wiley & Sons, Inc.
A differential scanning calorimetric study of chymotrypsin in the presence of added polymers
Authors: Otamiri Marina , Adlercreutz Patrick , Mattiasson Bo 
Published: December 2004

AbstractScanning calorimetry measurements of different amounts of chymotrypsin in water alone gave a temperature of denaturation (Td) value of 54°C. However, when high‐molecular‐weight poly(ethylene glycol) was added to aqueous solutions of chymotrypsin, the thermostability of the enzyme was enhanced. For example, the addition of 20% (w/w) of poly(ethylene glycol) of molecular weight of 100,000 increased the Td/ value to 66°C. In toluene containing various amounts of added water, ethyl cellulose was used to improve the thermostability of chymotrypsin. For this system, a Td value of 82°C was obtained with a 20% (w/w/) concentration of ethyl cellulose and 2% (v/v) of added water. Polymers in these solvents interact with water, which could otherwise denature the enzyme; polymers also from complexes with enzyme molecules to produce a more stable structure. © 1994 John Wiley & Sons, Inc.
Fuzzy supervisory control of glutamic acid production
Authors: Kitsuta Yoichi , Kishimoto Michimasa 
Published: December 2004

AbstractIn glutamic acid fermentation, the molasses feeding policy and time of penicillin addition significantly affected glutamic acid production, and a fuzzy supervisory control system was developed for their quasi‐optimal regulation.From the trend of the experimental data, production rules and membership functions of fuzzy inference were devised to determine the quasi‐optimum molasses feeding policy and penicillin addition time. A computer with multitasking operating system was used for the construction of the control system with fuzzy inferencing, which decided the control policy every minute, and the feed rate was controlled automatically. The pattern of residual sugar concentration was almost the same as that of maximum glutamic acid production under manual operation. Using the computer control system, stable production was maintained at the highest level of 71 to 75 g/L. © 1994 John Wiley & Sons, Inc.
Unified kinetic treatment for growth on dual nutrients
Authors: Haas Charles N. 
Published: December 2004

AbstractThis paper presents a new formulation for the analysis of growth kinetics on multiple nutrients. The baseline for the theory is the concept that a noninteractive growth process occurs among perfectly substitutable nutrients if the locus of points of the substrate concentrations producing equal growth rate is linear. A deviation function is then defined with respect to this base case, and several models for this function are suggested. The underlying theory is taken by analogy with mixture thermodynamics. The proposed formulation is tested against data in the literature on growth under substitutable and complementary substrate mixtures. © 1994 John Wiley & Sons, Inc.
Biochemistry of growth inhibition by ammonium ions in mammalian cells
Authors: Ryll Thomas , Valley Ulrich , Wagner Roland 
Published: December 2004

AbstractThe intracellular pool of UDP‐N‐acetylglucosamine and UDP‐N‐acetylgalactosamine has been shown to act as a central target during the inhibitory action of ammonium ions in vitro cultivated mammalian cell cultures. This pool has been demonstrated to be elevated at the end of a batch cultivation and very quickly as a response to exogenously applied ammonium chloride by using four different cell lines (hybridoma, BHK, CHO, and Ltk−929). The amount of enlarged UDP aminohexoses is correlated to the inhibitor concentration and additionally dependent on the cell line. The formation of the UDP sugars is associated with a transient reduction of the UTP pool. Moreover, the quick formation of UDP‐GNAc is strictly dependent on the presence of glucose and ammonium. Both metabolites act as biochemical precursors. Additionally, the formation of UDP‐GNAc after ammonium application has been shown to increase with an elevated cultivation pH and to be independent of the inhibition of transcription and translation processes. The intracellular amount of UDP‐GNAc correlates with the level of growth inhibition in mammalian cell lines. © 1994 John Wiley & Sons, Inc.
Improvement of the extraction of penicillin acylase from Escherichia coli cells by a combined use of chemical methods
Authors: Novella Isabel S. , Fargues Claire , GréVillot Georges 
Published: December 2004

AbstractSeveral techniques for protein extraction were tested for recovering penicillin acylase from a recombinant strain of Escherichia coli. These techniques include chemical [guanidine hydrochloride, Triton X‐100, ethylenediaminetetraacetic acid (EDTA), ethanol/toluene], physical (sonication, freeze‐and‐thawing), and enzymatic (lysozyme) treatments. Best results were obtained with the combined use of guanidine and EDTA. This extraction procedure was optimized, and it was found that 95% of the enzyme was extracted after a 10 m/M EDTA plus 10 mM guanidine treatment at room temperature for 10 h. The purification factor was 25 when compared to disruption by sonication. This extraction method could avoid purification steps for particular applications. © 1994 John Wiley & Sons, Inc.
Hyphal vocuolation and fragmentation inpenicillium chrysogenum
Authors: Paul G. C. , Kent C. A. , Thomas C. R. 
Published: December 2004

AbstractA link between vacuolation and fragmentation of Penicillium chrysogenum mycelia in stirred tank submerged fermentations is reported. Quantitative information on vocuolation and morphology was obtained by image analysis. In fed‐batch fermentations the coincidence of the events of rapid vacuolation and the fall of the mean total and main hyphal lengths suggests that hyphal fragmentation is not necessarily due to “shear” alone. The physiological state of the hyphae, characterized by the proportions of vaccuoles, was found to have a significant influence on the breakage of mycelial hyphae, It was found that the fragmentation was greater when the hyphae became heavily vacuolated following nutrient limitation in the culture, i.e., during the switch from the rapid growth to the production phase. © 1994 John Wiley & Sons, Inc.
Solid‐state enzyme deactivation in air and in organic solvents
Authors: Toscano Giuseppe , Pirozzi Domenico , Maremonti Michele , Greco Guido 
Published: December 2004

AbstractThermal deactivation of solid‐state acid phosphates (E.C. 3.1.3.2, from potato) is analyzed, both in the presence and in the absence of organic solvents. The thermal deactivation profile departs from first order kinetics and shows an unusual activity. The process is described by a phenomenological equation, whose theoretical implications are also discussed. The total amount of buffer salts in the enzyme powder dramatically affects enzyme stability in the range 70×C to 105×C. The higher salt/protein ratio increases the rate of thermal deactivation. The deactivation rate is virtually unaffected by the presence of organic solvents, independent of their hydrophilicity. © 1994 John Wiley & Sons, Inc.
Ion exchange immobilization of changed β‐galactosidase fusions for lactose hydrolysis
Authors: Heng Meng H. , Glatz Charles E. 
Published: December 2004

AbstractThe use of charged peptides fused to enzymes for immobilization onto ion‐exchange membranes was explored for the enzyme ×‐galactosidase. The additional charged peptides, containing 1, 5, 11, and 16 aspartates, fused to ×‐galactosidase, for the most part did not interfere with the kinetic behavior for lactose hydrolysis. There was a 2‐fold decline in Vm for the 16‐aspartate fusion, but the others were quite similar to the wild type enzyme (BGWT). BGWT and the fusions all retained approximately 50% of their activities when adsorbed onto ion‐exchange membranes. In contrast to BGWT, the enhanced binding strength of the 11 aspartate fusion provided the ability to hydrolyze whey permeate at 0.3 M ionic strength without enzyme leakage, and to immobilize the enzyme directly from diluted cell extract with 83% purity. © 1994 John Wiley & Sons, Inc.
Modified monoclonal antibody production kinetics kappa/gamma mRNA levels, and metabolic activities in a murine hybridoma selected by continuous Culture
Authors: Merten O.‐W. , Moeurs D. , Keller H. , Leno M. , Palfi G. E. , Cabanié L . , Couvé E. 
Published: December 2004

AbstractDuring long‐term continuous culture of the hybridoma cell line 11317, a better‐producing subclone (I1317‐SF11), giving improved productivity, has been selected. The comparison of the original cell line (I1317‐DC) with this subclone revealed that although the growth patterns of both clones were similar, both in continuous and in batch cultures, considerable differences could be seen between the clones with respect to monoclonal antibody (MAB) accumulation, MAB production rate, the levels of mRNA coding for heavy and light chains of IgG, and some metabolic activities. In continuous culture as well as in batch culture, I1317‐SF11 showed increased levels of mRNA coding for kappa and gamma chains compared with I1317‐DC and/or a modified ratio of the mRNA species when compared to that in I1317‐DC. Using pulse experiments, it could be established that the biosynthesis of both chains was augmented in I1317‐SF11. Although the kappa and gamma mRNA levels were modified or inversed for I1317‐SF11, the cells always synthesized more kappa than gamma chains. The overall increase in the synthetic activity of I1317‐SF11 is suggested as one reason for the considerable increase of IgG productivity and product accumulation in continuous culture as well as in repeated batch cultures. Tests concerning metabolic activity revealed that I1317‐SF11 had a predominantly glycolytic metabolism independent of growth requirements, whereas for I1317‐DC the metabolism became increasingly glycolytic with increased growth. The antibody yield coefficient of I1317‐SF11 on glutamine was significantly higher than that of I1317‐DC for the continuous culture, whereas the antibody coefficients on glucose were almost similar for both clones under the different culture conditions used. Both antibody coefficients were considerablly influenced by the specific growth rate.All these facts together lead to the conclusion that subclone I1317‐SF11 uses more of the energy available, or it was the energy and/or precursors available for the synthesis and production of MAB more efficiently than the thesis and production of MAB more efficiently than the original cell line. Although the levels of mRNA coding for heavy and light chains of IgG were modified, it could be confirmed that the overall regulation of MAB‐synthesis and ‐production occurs post‐translationally and that at higher growth rates, more biosynthetic activity is diverted to biomass production. © 1994 John Wiley & Sons, Inc.
Specific quantification of trichoderma reesei cellulases in reconstituted mixtures and its application to cellulase–cellulose binding studies
Authors: Nidetzky Bernd , Claeyssens Marc 
Published: December 2004

AbstractSpecific quantifications of the major cellulolytic components of the Trichoderma reesei enzyme complex, i.e., endoglucanases I and III and cellobiohydrolases I and II, are described and, employing a defined mixture of these four cellulases reconstituted according to the composition of the native Trichoderma cellulase complex, used to determine the binding of each individual component onto filter paper. During substrate degradation by this enzyme mixture, the specific adsorption of each individual cellulase gradually increases and no preferential binding of one enzyme component in any particular phase of cellulose hydrolysis is found. T. reesei cellobiohydrolases I and II admixed with endoglucanases I and III represent a “full‐value” cellulase system that is capable of degrading semicrystalline cellulose efficiently. In comparison with the crude Trichoderma enzyme complex, almost identical adsorption properties and similar hydrolytic efficiency are found for the reconstituted mixture. © 1994 John Wiley & Sons, Inc.