bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of polymeric adsorbents on the production of sanguinarine by Papaver somniferum cell cultures
Authors: Williams Robert D. , Chauret Nathalie , Bédard Charles , Archambault Jean 
Published: December 2004

AbstractThe suitability of adsorbent polymeric resins, Amberlite XAD‐4 and XAD‐7 (Rohm and Hass, Inc.), was investigated for the accumulation of sanguinarine from Papaver somniferum cell cultures. The adsorption and desorption of sanguinarine from aqueous solution was most effective with XAD‐7. In addition to sanguinarine, the resins were found to absorb growth regulators and vitamins from the culture medium. Growth inhibition was overcome by delaying for ∼4 days resin addition after cell inoculation in fresh medium. Resin addition (5% wt/vol) to actively growing uneclicited cultures led to increases in sanguinarine production and release of 30% to 40% and 60%, respectively. The addition of resins to elicited cultures led to increases in alkaloid production of up to 50% to 85% with similar increases in alkaloid release as observed for nonelicited cells. Overall yield of sanguinarine increased from 21 mg · g biomass dry weight−1 (dw) for elicited cultures to more than 39 mg · gdw−1 when elicitation was combined with resin addition. Higher quantities of resin (10% to 20% wt/vol) increased marginally the release of sanguinarine into the medium, and on the resin, up to 85% of total production. The use of resin appears promesing for the development of a bioprocess for sanguinarine production by cultured plant cells. © 1992 John Wiley & Sons, Inc.
Tyrosinase reaction/chitosan adsorption for selectively removing phenols from aqueous mixtures
Authors: Payne Gregory F. , Sun Wei‐Qiang , Sohrabi Afshin 
Published: December 2004

AbstractThe goal of this work was to explore the technical feasibility of an enzymatic approach as an alternative to traditional approaches for phenol separations. Specifically, we examined a two‐step approach to selectively remove phenols from mixtures containing nonphenolic isomers. Our model solutes, of molecular formula C7H8O, were the phenol, cresol; the alkyl aryl ether, anisol; and the alcohol, benzyl alcohol. The first step is this two‐step approach employed the enzyme mushroom tyrosinase to selectively convert the phenolic, presumably to an o‐quinone product. The tyrosinase was specific for the phenol and was not observed to react with either the ether or the alcohol. The second step of this two‐step approach employed a sorbent of an appropriate surface chemistry to bind the products of the tyrosinase‐catalysed reaction of phenols. The sorbent used for this study was chitosan. Chitosan was observed to be unable to adsorb either nonphenol and was unable to adsorb unreacted cresol. However, Chittosan effectively adsorbs UV‐absorbing reaction products of the tyrosinase‐catalysed reaction of phenols. When mixtures of cresol and either anasol or benzyl alcohol were studied, the two‐step approach was effective for completely removing the phenolic without loss of either the ether or alcohol or the ether (i.e., phenols were removed with high separation factors).
Kinetic studies on urea hydrolysis by immobilized urease in a batch squeezer and flow reactor
Authors: Huang Ting‐Chia , Chen Dong‐Hwang 
Published: December 2004

AbstractThe immobilization of urease on the reticulated polyurethane foam, and the kinetic phenomenon of urea hydrolysis by the resulting immobilized urease in both batch squeezer and circulated flow reactors were studied. Urease was immobilized with bovine serum albumin and glutaraldehyde on polyurethane foam support of 7 to 15 μm thickness. The residual apparent activity of urease after immobilization was about 50%. The good hydrodynamic property and flexibility of polyurethane foam were retained in solution after immobilization. A modified biofilm reactor model was used to describe the kinetic phenomenon of urea hydrolysis in both batch squeezer and circulated flow reactors. The characteristic parameters of the reactor model for both bioreactors were obtained by combining the Rosenbrock optimization method, the Rungs–Kutta method, and the Newton–Raphson method. The best‐fit results were in good agreement with the experimental data. This study suggests another application of polyurethane foam in enzyme immobilization and immobilized enzyme reactors, which offers potential for practical applications in various bioreactors. © 1992 John Wiley & Sons, Inc.
An investigation of the diffusion‐limited growth of animal cells around single hollow fibers
Authors: Sardonini Charles A. , Dibiasio David 
Published: December 2004

AbstractTo compare modeling with experimental data of cell growth surrounding individual fibers, the growth profiles of hybridoma cells in the extracapillary space of single hollow fiber bioreactors were examined. Agarose was provided in the extracapillary space to provide support and minimize convection. By sacrificing bioreactors at various time intervals, the growth profiles of cells surrounding a single hollow fiber could be monitored with increasing time. Using photomicroscopy and viable staining, areas of viable and nonviable cell growth were examined at various stages of development ranging from initial seeding to stable growth conditions. Cells were found to act as nucleation sites for the growth of individual colonies within the agarose. Profiles at stable growth conditions resulted in a thick cell mass near the surface of the fiber wall followed by cell colonies of decreasing size with increasing radial distance. A simplified theoretical model for cell growth was developed using mass balance equations for substrate penetration into individual cell colonies as well as away from the wall of a single fiber. The resulting profiles derived from theory were compared with experiments and found to be in good agreement for entering oxygen concentrations of 5% and 20%. © 1992 John Wiley & Sons, Inc.
A unified stoichiometric model for oxidative and oxidoreductive growth of yeasts
Authors: Auberson Lillian C. M. , von Stockar U. 
Published: December 2004

AbstractYeasts degrade glucose through different metabolic pathways, where the choice of the pathway is dependent on the nature of the limitation in the various substrates. When oxygen is limiting in addition to glucose, yeasts often grow according to a mixture of oxidative and reductive metabolism. Oxygen may be limiting either by supply or by inherent biological restrictions such as the respiratory bottleneck in Saccharomyces cerevisiae or by both. A unified model incorporating both supply and biological limitations is proposed for the quantitative prediction of growth rates, consumption and production rates, as well as key metabolite concentrations during mixed oxidoreductive metabolism occuring as a result of such oxygen limitations. This simple unstructured model can be applied to different yeast strains while at the same time requiring a minimum number of measured parameters. “Estimators” are utilized in order to predict the presence of supply‐side or biological limitations. The values of these estimators also characterize the relative importance of oxidative to total metabolism. Results from the aerobic and oxygen‐limited chemostat cultures were used to corroborate the model predictions. During these experiments, the heat released by the yeast cultures was also monitored on‐line. The model correctly predicted the overall stoichiometry, steady‐state concentrations, and rates including heat dissipation rates measured in the various situations of oxygen limitations. Direct continuous measurements such as heat can be used in conjunction with the unified model for on‐line proces control. © 1992 John Wiley & Sons, Inc.
Binding isotherms for soluble immobilized affinity ligands from spectral titration
Authors: Mayes A. G. , Eisenthal R. , Hubble J. 
Published: December 2004

AbstractThe method of spectral titration has been applied to binding equilibria between proteins and soluble immobilized ligands and evaluated using the interaction between Cibacron blue–dextran conjugates and lysozyme. The method is both simple and rapid and provides a convenient screening technique for characterization of soluble adsorbents designed for use in aqueous two‐phase affinity extraction or as liquid‐phase models for affinity chromatography systems. The results indicate that regardless of ligand density a constant 28% of the total coupled dye is available for high‐affinity protein binding at saturation. The dissociation constant for the dye–protein interaction, however, decreases with dye loading. The potential for kinetic investigations has been demonstrated using a stopped‐flow apparatus. The results indicate that a simple rate equation is inadequate to describe the data for lysozyme binding to dye–dextran conjugates. A modified model, which better describes the data, was developed by including a second rate limiting process, the transition from stacked to unstacked dye ligands on the dextran backbone. This effect could have practical significance for protein binding kinetics in affinity chromatography, especially in high‐performance liquid affinity chromatography applications where mass transfer is rapid. © 1992 John Wiley & Sons, Inc.
On‐line monitoring of hybridoma cell growth using a laser turbidity sensor
Authors: Konstantinov Konstantin B. , Pambayun Rindit , Matanguihan Ricaredo , Yoshida Toshiomi , Perusicn Cheryl M. , Hu Wei‐Shou 
Published: December 2004

AbstractA high‐sensitivity turbidity probe was used for on‐line monitoring of the cell concentration in batch hybridoma cultivation. Good correlation between off‐line cell counts and the linearized sensor signal was found. The quality of the signal was sufficiently high to provide for on‐line estimation of the specific growth rate using an efficient filtering procedure. These positive results suggest that such laser turbidity sensors will facilitate development of systems for on‐line monitoring and control of animal cell cultivations. © 1992 John Wiley & Sons, Inc.
Biodegradation of chlorophenol mixtures by Pseudomonas putida
Authors: Dapaah Samuel Y. , Hill G. A. 
Published: December 2004

AbstractThe dynamic growth behavior of Pseudomonas putida has been studied when resting calls were inoculated into a growth medium containing inhibitory concentrations of mixtures of phenol and monochlorophenols. Resting cells inoculated into single carbon substrate media did not demonstrate enhanced cell lysis by any of the phenol substrates. The apprarent death rate was reduced as the concentrations of phenol or chlorophenols were increased. This behavior was modeled by employing a constant specific death rate (kd = 0.0075 h−1) and assuming all organic species result in a lag‐phase, specific growth rate which may be larger or smaller than kd.Logarithmic biomass growth on pure monochlorophenols did not occur within 2 weeks after inoculation. Logarithmic growth phases were only observed when the monochlorophenols were cometabolized with phenol. The delay time over which the lag phase exists increased exponentially with phenol concentration and linearly with monochlorophenol concentration. The log growth yield coefficient decreased linearly with monochlorophenol concentration.The lag‐phase, specific growth rate was found to decrease exponentially with the concentration of monochlorophenols. This resulted in a 50% lag growth rate inhibition for both 3‐ and 4‐chlorophenol of 9 ppm and for 2‐chlorophenol of only 2 ppm. The new, empirical correlations are shown to closely model the complete lag and log growth behavior ot P. putida on phenol and chlorophenol mixtures. © 1992 John Wiley & Sons, Inc.
Cultivator for NMR studies of suspended cell cultures
Authors: Meehan A. J. , Eskey C. J. , Domach M. M. , Koretsky A. P. 
Published: December 2004

AbstractWhen nuclear magnetic resonance (NMR) spectroscopy is employed for physiological experiments with suspended cells, providing for adequate nutrient and oxygen delivery is particularly important, because the inherent insensitivity of NMR requires that concentrated cell suspensions be used. In addition, it is desirable to be able to manipulate the growth rate of cells during a NMR experiment. To address these concerns, a continuous cell cultivator that provides convective oxygen and nutrient transport has been constructed for NMR experiments. The NMR detector coil is located within the cultivator volume. The location is advantageous because the rapid exchange of cells in and out of the coil leads to a small apparent spin lattice relaxation time, thus allowing for rapid pulsing and fast signal averaging. In this article we present the physical principles on which the cultivator's design is based. 31P spectra showing the response of continuously cultivated Saccharomyces cerevisiae cultures to a phosphate bolus and growth rate shift are then given. © 1992 John Wiley & Sons, Inc.
Kinetics of sterilization ofLactobacillus breviscells by the application of high voltage pulses
Authors: Jayaram Sheshakamal , Castle G. S. P. , Margaritis Argyrios 
Published: December 2004

AbstractThe technique of irreversible electroporation has been successfully applied to cause a lethal effect onLactobacillus breviscells suspended in phosphate buffer solution, Na2HPO4/NaH2PO4· H2O (0.845/0.186 mM) between parallel plane electrodes. Tests were carried out at different temperatures (24,45,60, and 80°C) to determine if there was a synergistic effect of temperature and electric pulse treatment on the destruction ofL. brevis. Experimental results indicate that the viability (logN/N0; whereN0andNare the number of cells survived per milliliter before and after pulse voltage application, respectively) ofL. brevisdecreased with electric field strengthEand temperatureTand treatment timett. The relations between log(N/N0) andttand log(N/N0) andEindicate that higher field strengths are more effective than higher treatment times in causing destruction ofL. breviscells. It was also found that as the temperature of the liquid medium containingL. breviscells increased from 24 to 60°C, the death rate ofL. breviscells increased with a decrease in the total treatment timett(pulse width × number of pulses applied). The application of an electric field strengthE= 25 kV/cm at 60°C and treatment timett= 10 ms resulted in very high destruction levels ofL. breviscells (N/N0= 10−9). In comparison with existing steam sterilization technology, this new method of sterilization using relatively low temperature and short treatment time could prove to be an excellent method to minimize thermal denaturation of important nutrient components in liquid media. © John Wiley & Sons, Inc.
Effect of subunit dissociation, denaturation, aggregation, coagulation, and decomposition on enzyme inactivation kinetics: I. First‐order behaviour
Authors: Lencki Robert W. , Arul Joseph , Neufeld Ronald J. 
Published: December 2004

AbstractEnzyme inactivation kinetics typically follows what would appear to be simple first‐order behavior. However, the inactivation process is known to involve a number of reversible (decomposition, denaturation) as well as irreversible (decomposition, aggregation, and coagulation) reactions. These reactions can combine to form a wide variety of reaction pathways which can potentially demonstrate complex inactivation kinetics. However, it was shown that with appropriate assumptions with regard to the relative magnitudes of the various reaction rates, many complex inactivation pathways can demonstrate apparent first‐order behavior. Thus, with this analysis, a more accurate interpretation of the slope of an activity versus time semi‐log plot can be obtained. © 1992 John Wiley & Sons, Inc.
Comparison of maximum production rates and optimum operating/design parameters in overloaded elution and displacement chromatography
Authors: Felinger Attila , Guiochon Georges 
Published: December 2004

AbstractThe results of a study of the optimization of the experimental conditions for maximum production rate in overloaded elution and displacement chromatography are discussed. This study is based on the use of the equilibrium‐dispersive model of chromatography and the competitive Langmuir isotherms to calculate individual band profiles in the elution and displacement modes, and of a simplex algorithm to optimize the production rate. The operating parameters (sample size, mobile phase velocity, and the displacer concentration in the displacement model) and the column design parameters (column length and average particle diameter) are optimized simultaneously. Binary mixtures having relative concentrations 3:1 and 1:3, and separation factors of 1.2 to 1.8 are investigated. One of our major results is that, in both modes of chromatography, the maximum production rate is achieved at very low values of the retention factors, k′, much lower than those used in current practice. In all cases, unless k′ exceeds greatly that optimum value, the production rate is higher in overloaded elution than in displacement chromatography. This is particularly true for the extraction of a minor component, which is eluted second. © 1993 John Wiley & Sons, Inc.
Rheological characterization of media containing Penicillium chrysogenum
Authors: Pedersen Annemarie Gade , Bundgaard‐Nielsen Mikael , Nielsen Jens , Villadsen John , Hassager Ole 
Published: December 2004

AbstractSamples from fed‐batch fermentations of Penicillium chrysogenum on complex medium are rheologically characterized. The behavior is well described by a power law model for which the parameters are estimates. Furthermore, two types of model media are characterized and compared with the real fermentation samples. Xanthan solutions are found to mimic the rheological properties of the filamentous fungi much better than carboxymethyl cellulose (CMC) solutions. © 1993 John Wiley & Sons, Inc.
Scaleup of ajmalicine production by plant cell cultures of Catharanthus roseus
Authors: Schlatmann J. E. , Nuutila A. M. , Van Gulik W. M. , ten Hoopen H. J. G. , Verpoorte R. , J Heijnen J. 
Published: December 2004

AbstractThe effect of scaleup on he production of ajmalicine by a Catharanthus roseus cell suspension culture in a selected induction medium were studied. In preliminary experiments it was observed that the culture turned brown and the production was inhibited upon transfer from a shake flask to a stirred bioreactor with forced aeration. Two factors were recognized as the potential origin of the differences between shake flask and bioreactor cultures: gas composition and mechanical shear forces. These factors were studied separately.By recirculating a large part of the exhaust gas, a comparable gas regime was obtained in a bioreactor as occurred in a shake flask cultures. This resulted in the absence of browning and a similar pattern of ajmalicine production as observed in shake flasks. The effect of shear forces could not be demonstrated. However, the experiments showed that the culture may be very sensitive to liquid phase concentrations of gaseous compounds. The effects of kLa, aeration rate, CO2 production rate, and influent gas phase CO2 concentration on the liquid phase CO2 concentration are discussed. © 1993 John Wiley & Sons, Inc.
Continuous bioconversion of n‐octane to octanoic acid by recombinant Escherichia coli (alk+) growing in a two‐liquid‐phase Chemostat
Authors: Favre‐Bulle Oliver , Weenink Erik , Vos Tera , Preusting Hans , Witholt Bernard 
Published: December 2004

AbstractEscherichia coli is able to grow on sugars in the presence of a bulk n‐alkane phase. When E. coli is equipped with the alk genes from Pseudomonas oleovorans, the resulting recombinant strain converts n‐alkanes into the corresponding alkanoic acids. To study the effects of growth rate and exposure to a bulk apolar phase on the physiology and the productivity of E. coli, we have grown this microorganism in two‐liquid‐phase continuous cultures containing 5% (v/v) n‐octane.In contrast to batch cultures of wild‐tape E. coli grown in the presence of n‐octane, cells remained viable during the entire continuous culture, which lasted 200 h. Bioconversion of n‐octane to n‐octanoic acid by a recombinant E. coli (alk+) in a two‐liquid‐phase continuous culture was made possible by optimizing both the recombinant host strain and the conditions of culturing the organism. Continuous production in such two‐phase systems has been maintained for the least 125 h without any changes in the product concentration in the fermentation medium. The volumetric productivity was determined as a function of growth rate and showed a maximum at a dilution rate D = 0.32 h−1, reaching a continuous production rate of 0.5 g octanoate/L · h (4 tons/m3 · year). © 1993 John Wiley & Sons, Inc.
Relieving effects of glycine and methionine from acetic acid inhibition in Escherichia coli fermentation
Authors: Han Keehyun , Hong Juan , Lim Henry C. 
Published: December 2004

AbstractAmong amino acids screened for their potential to relieve wild and recombinant Escherichia coli from the negative effects of acetic acid, glycine, and methionine showed a sparing effect. In the presence of 2 g/L of acetic acid, addition of 0.5 g/L of glycine or methionine resulted in either a complete recovery or a further enhancement in the specific growth rate, while the enhancement was significant but not fully complete in the presence of 4 g/L of acetic acid. The addition of 0.5 g/L of methionine alleviated the negative effect of acetic acid on recombinant E. Coli growth to produce more β‐lactamase, which was encoded by plasmid pUC18. In continuous fermentation the methionine effect on recombinant. E. coli metabolism depended on dilution rate; at high dilution rates, above 0.4 h−1, the methionine addition enhanced β‐lactamase production and reduced acetic acid formation, while at low dilution rates, below 0.3 h −1, the effect was reversed. In def‐batch fermentation with wild‐type E. Coli, cell growth rate and cell yield from glucose were enhanced with methionine addition, while the acetic acid concentration reached over 4 g/L. © 1993 John Wiley & Sons, Inc.
Are water‐immiscibility and apolarity of the solvent relevant to enzyme efficiency?
Authors: Narayan V. Satya , Klibanov Alexander M. 
Published: December 2004

AbstractThe question of whether the solvent's water‐immiscibility is relevant to enzymatic activity was addressed by assaying four different hydrolases (three lipases and one protease) in nine anhydrous solvents of similar hydrophobicities of which four were infinitely miscible with water and five were not. For no enzyme was a jump in activity observed upon a transition from water‐miscible to water‐immiscible solvent. The relevance of solvent apolarity to enzymatic efficiency was also examined. To this end, three groups of isomeric anhydrous solvents were selected where within each group of isomeric anhydrous solvents were selected where within each group one solvent was apolar (i.e., lacked a permanent dipole moment). For none of the four enzymes studied was activity significantly higher in apolar solvents than in their polar counterparts. Thus we conclude that often‐cited solvent's immiscibility with water and apolarity by themselves are irrelevant to enzymatic activity. © 1993 John Wiley & Sons, Inc.