bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of shear on the inactivation kinetics of the enzyme dextransucrase
Authors: Lencki Robert W. , Tecante Alberto , Choplin Lionel 
Published: December 2004

AbstractAn inactivation model previously developed to characterize the rate of enzyme activity loss in unstirred solutions was extended to take into account orthokinetic interactions resulting from convective mixing. A synergistic relationship between shear rate and temperature was observed; the rate of inactivation of the enzyme dextransucrase was unaffected by the action of shear below 25°C, but was increased by the shear rate at 30°C. Shear rate does not appear to influence the equilibrium between native and denatured dextransucrase either directly in solution or indirectly by augmenting the turnover of the gas–liquid interface. However, a second‐order plot of the inverse of relative activity (AO/A) versus Gt (shear rate × time) of dextransucrase at a constant temperature was linear because of the influence of shear on the coagulation of the denatured enzyme. The addition of 0.01 g L−1 of polyethylene glycol (MW 20,000) blocked this coagulation reaction, thereby completely inhibiting the shear‐induced inactivation of dextransucrase at 30°C. © 1993 John Wiley & Sons, Inc.
A simple model for the optimization of the extraction yield of antibiotics isolated from fermented broths by direct crystallization
Authors: Cardoso Joaquim Pereira 
Published: December 2004

AbstractThis article is concerned with the development of a model to maximize the overall yield of isolation of antibiotics recovered from fermented broths by the so‐called direct precipitation method. In this process, as in most antibiotics isolation processes, a second filtration of the semiexhaust mycellium from the first filtration, after slurrying it in water at the suitable pH, is required. The maximization of the overall yield of isolation implies the use of an optimal amount of water, measured as a volume to fermented broth mass ratio, which can be calculated by using the model derived here. The model also allows for the calculation of the partial and overall yields of the isolation process, and its validity is demonstrated by its ability to describe reasonably well the isolation data of two different tetracycline‐fermented broths produced according to two different technologies.The application of the model requires only the knowledge of easily obtainable fermented broth parameters and is illustrated for two different types of tetracycline‐fermented broths. Although the model had been derived for the optimization of the overall yield of isolation of antibiotics recovered by direct precipitation, it can easily be adapted to be used for the optimization of the overall yield of isolation of antibiotics recovered by other isolation processes. © 1993 John Wiley & Sons, Inc.
Production of Bacillus thuringiensis spores in total cell retention culture and two‐stage continuous culture using an internal ceramic filter system
Authors: Kang Byung Chul , Lee Sang Yup , Chang Ho Nam 
Published: December 2004

AbstractThe production of Bacillus thuringiensis spores was investigated in a bioreactor incorporating a ceramic membrane filter to improve spore concentration and volumetric productivity. Two cultivation methods were used in this study: a total cell retention culture (TCRC), and a two‐stage continuous culture with partial cell bleeding. In the TCRC, fed by 50 g/L of glucose, a spore concentration of 1.6 × 1010 CFU/mL was obtained with a spore percentage of greater than 95% and a maximum cell mass of 82.2 g/L. The volumetric productivity was four times higher than that obtained from batch cultivation. In the two‐stage continuous culture with partial cell bleeding spore concentration was strongly dependent on the bleed ratio. The spore concentration of 1.8 × 109 CFU/mL and the spore percentage of 70% were obtained at the second stage when a bleed ratio of 0.33 and a dilution rate of 0.23 h−1 were used. © 1993 John Wiley & Sons, Inc.
Foreign gene expression (β‐galactosidase) during the cell cycle phases in recombinant CHO cells
Authors: Gu Man Bock , Todd Paul , Kompala Dhinakar S. 
Published: December 2004

AbstractRecombinant mammalian cultures for heterologous gene expression typically involve cells traversing the cell cycle. Studies were conducted to characterize rates of accumulation of intracellular foreign protein in single cells during the cell cycle of Chinese hamster ovary (CHO) cells transfected with an expression vector containing the gene for dihydrofolate reductase (dhfr) and the lacZ gene for bacterial β‐galactosidase (a nonsecreated protein). The lacZ gene was under the control of the constitutive cytomegalovirus promoter. These normally attachment‐grown cells were adapted to suspension culture in 10−7 M methotrexate, and a dual‐laser flow cytometer was used to simultaneously determine the DNA and foreign protein (β‐galactosidase) content of single living cells. Expression of β‐galactosidase as a function of cell cycle phase was evaluated for cells in the exponential growth phase, early plateau phase, and inhibited traverse of the cell cycle during exponential growth. The results showed that the β‐galactosidase production rate is higher in the S phase than that in the G1 or G2/M phases. Also, when cell cycle progression was stopped at the S phase by addition of aphidicolin, β‐galactosidase content in single cells was higher than that in exponential phase or plateau phase cells and increased with increasing culture time. Although the cells did not continue to divide after aphidicolin addition, the production of β‐galactosidase per unit volume of culture was very similar to that in normal exponential growth. © 1993 John Wiley & Sons, Inc.
Rapid renaturation of denatured and aggregated proteins using liquid paraffin as a pseudolipid bilayer membrane
Authors: Yoshii Hidefumi , Kojima Tsugio , Furuta Takeshi , Yasunishi Akira 
Published: December 2004

AbstractA means of rapidly renaturing denatured protein was devised and evaluated. Three liquids were laminarly layered in a centrifuge tube, in which two solutions sandwiched liquid paraffin so as to form a pseudolipid bilayer. Denatured and aggregted protein placed on the upper surface of liquid paraffin was renatured as it passed through liquid‐paraffin layer into the renaturation buffer during the centrifugation. The aggregated and denatured protein selectively passed through the liquid‐paraffin layer, whereas other solutions, such as chaotropic agents or organic solvent, could not. This means that a rapid dilution condition favorable for protein renaturation was realized in a small scale. Aggregated and denatured BSA and ribonuclease A were renatured and resolubilized as they passed through the liquid‐paraffin layer into an appropriate renaturation buffer solution. This method was also applied to the rapid heme reconstitution of myoglobin from Feprotoporphyrin IX to Zn‐protoporphyrin IX. © 1994 John Wiley & Sons, Inc.
Increased thermostability of Asn182 → Ala mutant Aspergillus awamori glucoamylase
Authors: Reilly Peter J. , Chen Hsiu‐Mei , Bakir Ufuk , Ford Clark 
Published: December 2004

AbstractAsn182 → Ala Aspergillus awamori glucoamylase expressed in Saccharomyces cerevisiae had a first‐order thermodeactivation coefficient 40% that of wild‐type glucoamylase at pH 4.5 between 60° and 65°C, caused by the elimination of an Asn—Gly sequence subject to deamidation and eventual chain breakage. Above 70°C, and at pHs 3.5 and 5.5, thermodeactivation coefficients of wild‐type and mutant enzymes were roughly equal, because the fastest deactivation mechanism was no longer deamidation. The mutation had little effect on the enzyme's optimal pH for activity and subsite map, or on the glucose yield from starch dextrin hydrolysis. During enzyme production by yeast fermentation, highest cell densities and activities of wild‐type and mutant glucoamylases were attained after a period of glucose starvation, followed by a second addition of glucose. © 1994 John Wiley & Sons, Inc.
Kinetics of chondrocyte growth in cell‐polymer implants
Authors: Freed L. E. , Marquis J. C. , Langer R. , Vunjak‐Novakovic G. 
Published: December 2004

AbstractIn vitro cultivation of cartilage cells (chondrocytes) on biodegradable polyglycolic acid (PGA) scaffolds resulted in implants which could potentially be used to repair damaged joint cartilage or for reconstructive surgery. Cell growth kinetics were studied to define conditions under which the cellularity of implants made from isolated calf chondrocytes reached that of the parent calf cartilage. In static cultures, condrocyte growth rates decreased as either implant thickness or implant cell density increased. Over 4 weeks of cultivation, implant permeability to glucose decreased to 3% that of the plain polymer scaffold; this effect was attributed to the decrease in effective implant porosity associated with cartilage tissue regeneration.In a well‐mixed culture, implants 1 cm in diameter by 0.3 cm thick maintained high cell growth rates over 7 weeks and hard normal cell densities. Regenerated cartilage with these dimensions is large enough to resurface small joints such as the trapezium bone at the base of the human thumb. Such implants could not be grown statically, since cell growth stopped at 3–4 weeks and cell densities remained below normal. Optimization of the tissue culture environment is thus essential in order to cultivate clinically useful cartilage implants in vitro. © 1994 John Wiley & Sons, Inc.
Oxygen is a factor determining in vitro tissue assembly: Effects on attachment and spreading of hepatocytes
Authors: Rotem Avi , Toner Mehmet , Bhatia Sangeeta , Foy Brent D. , Tompkins Ronald G. , Yarmush Martin L. 
Published: December 2004

AbstractMany recent studies related to the development of bioartificial liver devices have utilized hepatocytes cultured within devices of various geometries. Because hepatocytes are anchorage‐dependent cells, they need to attach and spread onto the extracellular matrix to be able to function, a process that requires energy. Thus, it is important to deliver enough oxygen to hepatocytes contained within bioartificial liver devices during the early phase of cellular organization while the cells interact with the extracellular matrix. In this study, we investigated the effect of oxygen on the attachment and spreading of hepatocytes. Increasing the gas phase oxygen from 0 to 160 mmHg resulted in an increase in the percentage of cells attaching from 43.0 ± 5.8% to 103.6 ± 29%, 1 h after seeding. In a similar manner, increasing the gas phase oxygen from 0 to 160 mmHg resulted in an increase of the projected surface area from 310 ± 35 to 827 ± 127 μm2, 24 h after seeding. Furthermore, the partial pressure of oxygen at the cell level was estimated using a diffusion‐reaction model. The model indicated that a cell surface oxygen partial pressure of 0.064 mmHg was required for the half‐maximal (K) attachment of hepatocytes to collagen‐based substrate. On the other hand, the K value of the spreading process was predicted to be 0.13 mmHg. The results of this study demonstrate the importance of oxygen during the initial stages of attachment and spreading of hepatocytes, and it has important implications in the design of hepatocyte‐based bioartificial liver devices. © 1994 John Wiley & Sons, Inc.
Facilitated transport of lactic acid in a stirred transfer cell
Authors: Lazarova Z. , Peeva L. 
Published: December 2004

AbstractThe application of liquid membrane extraction to the recovery of lactic acid from model systems and fermentation media was investigated. An experimental study of the facilitated transport of lactic acid using ALIQUAT 336 as a mobile carrier in a stirred transfer cell is reported. The effect of stirring speed, initial lactic acid concentration, carrier concentration, and NaCl as a reagent in the acceptor phase are considered. © 1994 John Wiley & Sons, Inc.
Biodegradation of pesticides in nonionic water‐in‐oil microemulsions of tween 85: Relationship between micelle structure and activity
Authors: Komives Claire F. , Lilley Erin , Russell Alan J. 
Published: December 2004

AbstractWater‐in‐oil microemulsion systems have been studied in recent years for a number of applications in protein separation and enzymology. Although it is well established that reversed micelle systems provide an excellent medium for nonaqueous biocatalytic studies, there is still much speculation as to the interaction of the enzyme with the surfactant interface. Polyoxyethylene sorbitan trioleate (Tween 85) is a nonionic surfactant which has some interesting properties for microemulsion formation and protein solubilization. In conjunction with a separate article describing the structural features of Tween 85 reversed micelles in hexane with isopropanol as a cosurfactant, this work describes the activity of an enzyme, organophosphorus hydrolase, for degrading organophosphorus pesticides in this microemulsion system. Ternary phase diagrams were constructed to outline the phase boundaries at different temperatures and isopropanol concentrations, which elucidate the role of the cosurfactant alcohol, as well as some features of micelle structure. Kinetic and stability studies with organophosphorus hydrolase show the effect of enzyme partitioning between the micelle surfactant layer and aqueous core. © 1994 John Wiley & Sons, Inc.
Effect of solution pH and ionic strength on the separation of albumin from immunoglobulins (IgG) by selective filtration
Authors: Saksena Skand , Zydney Andrew L. 
Published: December 2004

AbstractAlthough protein fractionation by selective membrane filtration has numerous potential applications in both the downstream processing of fermentation broths and the purification of plasma proteins, the selectivity for proteins with only moderately different molecular weights has generally been quite poor. We have obtained experimental data for the transport of bovine serum albumin (BSA) and immunoglobulins (IgG) through 100,000 and 300,000 molecular weight cutoff polyethersulfone membranes in a stirred ultrafiltration device at different solution pH and ionic strength. The selectivity was a complex function of the flux due to the simultaneous convective and diffusive solute transport through the membrane and the bulk mass transfer limitations in the stirred cell. Under phsioligical conditions (pH 7.0 and 0.15MNaCI) the maximum selectivity for the BSA‐IgG separation was only about 2.0 due primarily to the effects of protein adsorption. In contrast, BSA‐IgG selectivities as high as 50 were obtained with the same membranes when the protein solution was at pH 4.8 and 0.0015MNaCl. This enhanced selectivity was a direct result of the electrosatatic contributions to both bulk and membrane transport. The membrane selectivity could actually be reversed, with higher passage of the larger IgG molecules, by using a 300,000 molecular weight cutoff membrane at pH 7.4 and an ionic strength of 0.0015MNaCl. These results clearly demonstrate that the effectiveness of selective protein filtration can be dramatically altered by appropriately controlling electrostatic interactions through changes in pH and/or ionic strength. © 1994 John Wiley & Sons, Inc.
Pervaporative butanol fermentation by Clostridium acetobutylicum B18
Authors: Geng Qinghuang , Park Chang‐Ho 
Published: December 2004

AbstractExtractive acetone‐butanol–ethanol (ABE) fermentation was carried out successfully using pervaporation and a low‐acid‐producing Clostridium acetobutylicum B18. A pervaporation module with 0.17 m2 of surface area was made of silicone membrane of 240 μm thickness. Pervaporation experiments using make‐up solutions showed that butanol and acetone fluxes increased linearly with their concentrations in the aqueous phase. Fickian diffusion coefficients were constants for fixed air flow rates, and increased at higher sweep air flow rates. During batch and fed‐batch fermentations, pervaporation at an air flow rate of 8 L/min removed butanol and acetone efficiently. Butanol concentration was maintained below 4.5 g/L even though Clostridium acetobutylicum B18 produced butanol steadily. Pervaporation could not remove organic acids efficiently, but organic acids did not accumulate because strain B18 produced little organic acid and recycled added organic acids efficiently. With pervaporation, glucose consumption rate increased compared to without pervaporation, and up to 160 g/L of glucose was consumed during 80 h. Cell growth was not inhibited by possible salt accumulation or oxygen diffusion through the silicone tubing. The culture volume was maintained relatively constant during fed‐batch operation because of an offsetting effect of water and product removal by pervaporation and addition of nutrient supplements. © 1994 John Wiley & Sons, Inc.
Photolithotrophic cultivation of Laminaria saccharina gametophyte cells in a stirred‐tank bioreactor
Authors: Qi Hans , Rorrer Gregory L. 
Published: December 2004

AbstractFilamentous cell cultures derived from female gametophytes of the temperate brown macroalga Laminaria saccharina were photolithotrophically cultivated in artificial seawater medium within an illuminated 1.3‐L stirred‐tank bioreactor at 13°C using CO2 in air as the carbon source. A Monod model adequately described light‐saturated growth. The apparent half‐saturation constant (Ko) was 23 μE/m2‐s, and maximum specific growth rate was 0.15 day−1. At a constant inoculation cell density of 50 mg DCW/L, biomass productivity after 26 days of cultivation increased from 630 mg DCW/L at 18 μE/m2‐s to 890 mg DCW/L at 228 μE/m2‐s. At 98 μE/m2‐s, 1.1 vvm aeration rate, and 250 rpm impeller speed, the CO2 transfer rates (CO2 TRs) and CO2 consumption rates (r) were determined over the cultivation period. At peak CO2 demand, the maximum CO2 TR was 0.19 mmol CO2/L‐h, but r was only 0.15 mmol CO2/L‐h, implying that the culture was not CO2 transport limited. This is the first reported bioreactor cultivation study of cell cultures derived from a macrophytic marine alga. © 1995 John Wiley & Sons, Inc.
Kinetics of nitrate inhibition of carbon tetrachloride transformation by a denitrifying consortia
Authors: Skeen Rodney S. , Valentine Nancy B. , Hooker Brian S. , Petersen James N. 
Published: December 2004

AbstractThe kinetics of nitrate inhibition of carbon tetrachloride (CT) transformation were examined using a denitrifying consortium. Comparison of data from fed‐batch experiments to the model reported by Hooker et al. indicate that the inhibition constant ranges between 3.2 and 21 mg/L, with an average of 8.8 mg/L. This range is much lower than the previously reported value of 169 mg/L. Simulations using the corrected parameter accurately reflect this new data and the data reported by Hooker et al. In contrast, the earlier reported coefficient value does not reflect the data reported in this work. © 1995 John Wiley & Sons, Inc.
Microbial production of (+)‐trans‐isochorismic acid
Authors: Schmidt Karsten , Leistner Eckhard 
Published: December 2004

AbstractTwo methods are described for the preparation of enantiomerically pure (+)‐trans‐isochorismic acid, an important metabolite of the postchorismate pathway. Both methods can be employed to prepare isotopically labeled isochorismic acid. One of the two methods is suitable to prepare bulk quantities of isochorismic acid using a recombinant strain of Klebsiella pneumoniae 62‐1. © 1995 John Wiley & Sons, Inc.
Intracellular flux analysis in hybridomas using mass balances and in vitro 13C nmr
Authors: Zupke Craig , Stephanopoulos Gregory 
Published: December 2004

AbstractIntracellular fluxes are important in defining cellular physiology and its changes in response to environmental variations. Stoichiometric balances combined with extra cellular metabolite measurements were applied to the estimation of intracellular fluxes and the study of energy metabolism in the hybridoma cell line ATCC CRL 1606. Redundant measurements allowed the evaluation of the consistency of the stoichiometry, measurements, and pseudo‐steady‐state assumption leading to refinement of the assumed biochemistry and identification of measurement errors. To validate the flux estimates, two batch experiments were performed with glucose labeled in the 1 position with 13C. The distribution of 13C in secreted lactate was measured via nuclear magnetic resonance spectroscopy (NMR) and compared to that predicted from the estimated intracellular fluxes. There was good agreement between the measured and estimated isotope distributions, demonstrating the validity of the flux estimates obtained from stoichiometric balances. © 1995 John Wiley & Sons, Inc.
Removal of phenols and aromatic amines from wastewater by a combination treatment with tyrosinase and a coagulant
Authors: Wada Shinji , Ichikawa Hiroyasu , Tastsumi Kenji 
Published: December 2004

AbstractRemoval of phenols and aromatic amines from industrial wastewater by tyrosinase was investigated. A color change from colorless to darkbrown was observed, but no precipitate was formed. Colored products were found to be easily removed by a combination treatment with tyrosinase and a cationic polymer coagulant containing amino group, such as hexamethylenediamine‐epichlorohidrin polycondensate, polyethleneimine, or chitosan. The first two coagulants, synthetic polymers, were more effective than chitosan, a polymer produced in crustacean shells. Phenols and aromatic amines are not precipitated by any kind of coagulants, but their enzymatic reaction products are easily precipitated by a cationic polymer coagulant. These results indicate that the combination of tyrosinase and a cationic polymer coagulant is effective in removing carcinogenic phenols and aromatic amines from an aqueous solution. Immobilization of tyrosinase on magnetite gave a good retention of activity (80%) and storage stability i.e., only 5% loss after 15 days of storage at ambient temperature. In the treatment of immobilized tyrosinase, colored enzymatic reaction products were removed by less coagulant compared with soluble tyrosinase. © 1995 John Wiley & Sons, Inc.
Esterification reactions catalyzed by Chromobacterium viscosum lipase in CTAB‐based microemulsion systems
Authors: Rees Gareth D. , Robinson Brian H. 
Published: December 2004

AbstractChromobacterium viscosum (CV) lipase solubilized in water‐in‐oil (w/o) microemulsions based on the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) have been used for multigram‐scale ester synthesis, including the kinetic resolution of a secondary alcohol. The stability of CV lipase in all the CTAB microemulsions studied was excellent and was superior to that observed in aqueous buffer at the same pH and temperature. Kinetic studies were performed using the synthesis of ethylhexadecanoate as a model reaction. Under pseudo‐first‐order conditions, the synthesis rates were linearlydependent on the enzyme and fatty acid concentrations and the R dependence shows the characteristic bell‐shaped curve (where R = [H2O]/[surfactant]). The dependence of enzyme activity toward octyldecanoate synthesis on the pH of the dispersed buffer phase is in marked contrast to that observed for the pH dependence of CV lipase toward p‐nitrophenylbutyrate hydrolysis. In the former case, the pH‐activity profile is approximately sigmoidal, which may reflect the ionization state of the fatty acid substrate. In the latter case, the pH dependence is minimal at both R = 10 and R = 50, suggesting the enzyme does not experience a changed pH environment. Inclusion of a pH‐sensitive probe molecule into those incubations containing fatty acid clearly demonstrates that the probe molecule experiences a changed environment consistent with that expected for the selected buffer. An in situ Fourier transform nuclear magnetic resonance (FT‐NMR) assay has been developed which allows continuous monitoring of the esterification reactions, thereby providing an additional means of determining initial rates. The method may be of general value for lipase assays in microemulsions since it may provide, at the same time, information regarding enzyme regioselectivity. © 1995 John Wiley & Sons, Inc.