bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel membrane bioreactor for detoxifying industrial wastewater: I. Biodegradation of phenol in a synthetically concocted wastewater
Authors: Livingston Andrew Guy 
Published: December 2004

AbstractA novel process has been used to biodegrade phenol present in an acidic (1 M HCI) and salty (5% w/w NaCl) synthetically bioreactor, in which the phenol present in the wastewater is separated from the inorganic components by means of a silicone rubber membrane. Transfer of the phenol from the wastewater and into a biological growth medium allows biodegradation to proceed under controlled conditions which are unaffected by the hostile inorganic composition of the wastewater. At a wastewater flow rate of 18 mL h−1 (contact time 6 h), 98.5% of the phenol present in the wastewater at an inlet concentration of 1000 mg was degraded; at a contact time of 1.9 h, 65% of the phenol was degraded. Phenol degradation was accompanied by growth of a biofilm on the membrane tubes and by conversion of approximately 80% of the carbon entering the system to CO2 carbon. Analysis of the transport of phenol across the membrane revealed that the major resistance to mass transfer arose in the diffusion of phenol across the silicone rubber membrane. A mathematical model was used to describe the transfer of phenol across the membrane and the subsequent diffusion and reaction of phenol in the biofilm attached to the membrane tube. This analysis showed that (a) the attached biofilm significantly lowers the mass transfer driving force for phenol across the membrane, and (b) oxygen concentration limits the phenol degradation rate in the biofilm. These conclusions from the model are consistent with the experimental results. © 1993 Wiley & Sons, Inc.
Continuous, high level production and excretion of a plasmid‐encoded protein by Escherichia coli in a two‐stage chemostat
Authors: Fu Jeffrey , Wilson David B. , Shuler Michael L. 
Published: December 2004

AbstractThe stable continuous overproduction of a plasmidencoded protein, β‐lactamase, for at least 50 days by Escherichia coli K‐12, RB791(pKN), with release into the culture medium has been demonstrated in two‐stage chemostats. The second‐stage culture was continuously induced with 0.1 mM IPTG. Continuous expression of β‐lactamase could not be sustained with this strain in a single‐stage chemostat because of cell death and selection for lac−1 cells. β‐Lactamase production in the second stage was sensitive to the second‐stage dilution rate and the distribution of the limiting substrate (i.e., glucose) between the first and second stages. The fraction of viable, excreting cells and the average copy number in the induced culture was measurably higher under those conditions of dilution rate and substrate distribution which yielded high β‐lactamase levels. The best operating conditions found at 20°C were a first‐stage dilution rate of 0.12 h−1, a second‐stage dilution rate of 0.03 h−1, and equal glucose feed supplied to each stage. Enzymatically active β‐lactamase was produced at a level of 25% of total cellular protein with 90% excretion yielding 300 mg β‐lactamase/L that was 50% pure at an OD600 < 6. © 1993 Wiley & Sons, Inc.
Affinity thermoprecipitatin: Contribution of the efficiency of ligand–protein interaction and access of the ligand
Authors: Galaev I. Yu. , Mattiasson B. 
Published: December 2004

AbstractConjugates to two thermoprecipitating polymers, poly(N‐vinyl caprolactam) and poly(N‐isopropylacrylmide), with soybean trypsin inhibitor, Cibacron Blue 3GA, Cu‐iminodiacetic acid, and p‐aminobenzamidine were synthesized. The interaction of these conjugates with trypsin and lactate dehydrogenase was studied. Coupling of the ligand to a polymer resulted in a 100‐1000‐fold decrease in enzyme‐affinity. Rough theoretical estimates revealed that a successful affinity precipitation required that the binding of a target protein and a ligand coupled to a polymer have binding constants on the order of 10−7‐10−8 M. Such strong affinity of low molecular weight ligands that can provide binding constants of 10−9‐10−11 M or alternatively multipoint attachment of the target protein molecule. The ligand in the ligand‐polymer conjugate is still accessible to the protein after thermoprecipitation, and the latter can bind with the particle of the dispersion of thermoprecipitated ligand‐polymer precipitate may result in stripping of enzyme molecules from the surface of the particles. © 1993 Wiley & Sons, Inc.
In situ fermentation monitoring with recombinant firefly luciferase
Authors: Lasko Daniel R. , Wang Daniel I. C. 
Published: December 2004

AbstractA novel method is described for the on‐line determination of viable cell number. It has been tested in fermentations of Escherichia coli. The cells are transfected with the gene for firefly luciferase and fed low levels of luciferin in the medium. The reaction requires ATP, so the nonviable cells cannot produce light. Thus, light production is linear with viable cell density from innoculation through most of exponential growth. The light emitted by these cells is then conducted from the reaction vessel to the light detection equipment by an optical fiber. With the equipment described below, as few as a 106 cells/mL, or an OD600 of 0.004, are easily detectable and concentrations greater than 1010 cells/mL are well within range. The data are collected by a computer, so adaptation to on‐line control applications is straightforward. During lag phase, this method is much more accurate then optical density measurements. At the end of exponential growth, rapid changes in light production mark carbon source depletion and the onset of cell lysis. A simple model accounts for the luciferin used during the fermentation and corrects the light detected to the proper cell density. © 1993 John Wiley & Sons, Inc.
Gluco‐oligosaccharide synthesis by free and immobilized β‐glucosidase
Authors: Ravet C. , Thomas D. , Legoy M. D. 
Published: December 2004

AbstractGluco‐oligosaccharides were synthesized through the enzymatic condensation of D‐glucose at high concentration using a commercial almond β‐glucosidase. The synthesis reactions were carried out with both free and immobilized enzyme, with or without sorbitol, an efficient depressor of water activity (aw) in the presence of different glucose concentrations. The yield and the composition of the gluco‐oligosaccharides produced changed with the reaction mixture and the form of the enzyme used (free or immobilized). The use of 5 M glucose solution permitted only disaccharides to be obtained, whereas with a glucose concentration of 7.5 M glucose, di‐, tri‐, and tetrasaccharides were produced. A 7.5 M glucose solution used with 4.4 M sorbitol gave three times more disaccharides than the same solution without sorbitol. Moreover, the immobilized enzyme was much more active in synthesis. The synthesis yield (oligomers mg/mL · mg of enzyme) after immobilization was 573% compared to that of the free enzyme, when a 7.5 M glucose solution was tested. The effects of substrate concentration, sorbitol addition and enzyme immobilization were investigated. © 1993 John Wiley & Sons, Inc.
Neural network modeling of batch cell growth pattern
Authors: Syu Mei‐Jywan , Tsao George T. 
Published: December 2004

AbstractThe capability of neural networks in modeling batch cell growth by providing initial conditions only is tested in this study. The neural network tested is of the back‐propagation‐type including a newly discovered saturation‐type transfer function. The simulation and prediction results of this neural network modeling will be demonstrated. © 1993 John Wiley & Sons, Inc.
Transport of sugars via two anomer‐specific sites on mannose–phosphotransferase system in Lactococcus cremoris: In vivo study of mechanism, kinetics, and adaptation
Authors: Benthin Stig , Nielsen Jens , Villadsen John 
Published: December 2004

AbstractGlucose uptake in Lactococcus lactis subsp. cremoris FD1 occurs via the mannose phosphotransferase system (Man–PTS), which is quite unspecific and allows transport of many different sugars and sugar analogues. It was previously shown (Benthin, S., Nielsen, J., Villadsen, J. Biotechnol. Bioeng. 40:137–146, 1992) that the kinetics of in vivo glucose uptake in a glucose‐limited chemostat culture is best described by assuming that the glucose transport system has two anomer‐specific sites with a relative uptake rate of 36% through the α‐site. In the present study, the existence of anomer‐specific sites on Man–PTS is shown by experiments where α‐glucose, β‐glucose, mannose, and 2‐deoxyglucose are added to glucose‐limited chemostat cultures. A quantitative description of the competitive uptake of the involved sugars at the two sites is given. In a mannose‐limited chemostat culture, the relative glucose flux via the α‐site is 50%, corresponding to a change toward the equilibrium composition of mannose (68%). Furthermore, when the feed to a mannose‐limited chemostat culture is changed to glucose, the rate of change of relative glucose flux through the α‐site corresponds to constitutive synthesis of Man–PTS with 36% α‐site stoichiometry in new cells. When N‐acetylglucosamine (73% α‐anomer at equilibrium) is the limiting substrate, the relative glucose flux through the α‐site is also 48% to 50%. With a feed of α‐glucose generated enzymatically from nonmetabolizable sucrose the relative glucose flux through the α‐site can be as high as 78%. Finally, growth in the presence of nonmetabolizable α‐methylglucoside leads to formation of cells with a relative glucose flux through the α‐site of 29% to 30%. The adaptation of the flux distribution between the α‐ and β‐site is tentatively explained by the hypothesis that two integral membrane proteins of Man–PTS are involved in this process. © 1993 John Wiley & Sons, Inc.
Analysis of metabolic fluxes in batch and continuous cultures of Bacillus subtilis
Authors: Goel Akshay , Ferrance Jerome , Jeong Jinwook , Ataai Mohammed M. 
Published: December 2004

AbstractIt is well recognized that metabolic fluxes are the key variables that must be determined in order to understand metabolic regulation and patterns. However, owing to difficulties in measuring the flux values, evaluation of metabolic fluxes has not been an integral part of the most metabolic studies. Flux values for metabolites of glycolysis, tricarboxylic acid (TCA) cycle, and hexose monophosphate (HMP) pathway were obtained for batch and glucose‐limited continuous cultures of Bacillus subtilis by combining the information from the stoichiometry of key biosynthetic reactions with the experimental data on concentrations of glucose and metabolic by‐products, CO2 evolution, and oxygen uptake rates. The results indicate that (1) the metabolic fluxes and energetic yield as well as the extent of flux mismatch in metabolic activity of glycolysis and the TCA cycle reactions can be accurately quantified; (2) the flux through the TCA cycle in continuous culture is much in excess of cell energetic and biosynthetic demands for precursors; (3) for the range of growth rates examined the TCA cycle flux increases almost in proportion to growth rate and is significantly repressed only at very high growth rates of batch cultures; and (4) for continuous cultures the isocitrate dehydrogenase catalyzed reaction of the TCA cycle is the major source of the reduced form of nicotinamide‐adenine dinucleotide phosphate (NADPH) used in biosynthesis. © 1993 John Wiley & Sons, Inc.
A single‐cell assay of β‐galactosidase in recombinant Escherichia coli using flow cytometry
Authors: Miao Fudu , Todd Paul , Kompala Dhinakar S. 
Published: December 2004

AbstractA flow cytometric method was developed for the assay of β‐galactosidase in single Escherichia coli cells. A new fluorogenic substrate for β‐galactosidase, C12FDG, contains a lipophilic group that allows the substrate to penetrate through cell membranes under normal conditions. When the substrate is hydrolyzed by intracellular β‐galactosidase, a green fluorescent product is formed and retained inside the cell. Consequently, the stained β‐galactosidase–positive cells exhibit fluorescence, which is detected by flow cytometry. This new assay was used to analyze the segregational instability caused by a reduction in specific growth rate of the plasmid‐bearing cells in the T7 expression system. Induction results in a substantial accumulation of intracellular β‐galactosidase along with a rapid increase in the fraction of plasmid‐free cells. Once the cells lose the plasmid, they no longer produce β‐galactosidase, which is reduced by at least half every generation; thus, after staining, the fluorescent, plasmid‐bearing cells can be distinguished from the nonfluorescent, plasmid‐free cells using flow cytometry. This article describes the feasibility of the flow cytometric assay for single E. coli cells and reports the optimal assay conditions. A direct relationship between β‐galactosidase activity and green fluorescence intensity was found, and the fractions of recombinant cells in batch cultures were analyzed after various levels of induction. © 1993 John Wiley & Sons, Inc.
Pressure affects enzyme function in organic media
Authors: Kim Jungbae , Dordick Jonathan S. 
Published: December 2004

AbstractPressure affects enzyme function in nonaqueous media. Activation volumes have been determined and provide evidence that the primary effect of pressure is to enhance the stripping of water off an enzyme in polar organic solvents and leads to decreased enzymatic activity. Activation volumes of subtilisin Carlsberg in organic solvents, particularly with the enzyme hydrated, have a larger magnitude than activation volumes determined in aqueous solutions. This study provides further evidence that enzymatic activity in polar organic solvents is dominated by the interaction of enzyme‐bound water with the solvent. From a practical standpoint, however, the results of this study suggest that enzymatic catalysis in organic solvents may be controlled by the combined effects of pressure and enzyme hydration. © 1993 John Wiley & Sons, Inc.
Lipase‐Catalyzed acyiation of sugars solubilized in hydrophobic solvents by complexation
Authors: Ikeda Isao , Klibanov Alexander M. 
Published: December 2004

AbstractBy complexing glucose and other mono‐ and disaccharides with phenylboronic acid, they were solubilized in many organic solvents. Pseudomonas sp. lipoprotein lipase readily acylated such solubilized sugars in these solvents (no reaction was observed without phenylboronic acid, i.e., when sugars are insoluble in the reaction medium). Solubilized D‐glucose was enzymatically acylated with vinyl acrylate on a preparative scale, and the resultant 6‐O‐acryloylglucose was chemically polymerized to yield a sugar‐based polyacrylate with a molecular weight of 14,000 Da. © 1993 John Wiley & Sons, Inc.
Factors affecting bio‐oxidation of sulfide minerals at high concentrations of solids: A review
Authors: Bailey A. D. , Hansford G. S. 
Published: December 2004

AbstractBio‐oxidation has proved to be a viable process for the oxidative pretreatment of refractory gold‐bearing sulfides. Generally, the oxidation rate is maximal at 20% solids for high sulfide content materials [ca. 30% sulfur]. Low grade ores [1% sulfur] have been successfully oxidized at 55% solids, indicating a link between the sulfide grade of the material and the optimal solids concentration for operation. Concentrations of high solids have been reported to lower oxidation rates, increase lag times, and decrease the ultimate extent of oxidation. This review discusses the various factors that have been proposed as causes of these phenomena. The factors include oxygen and carbon dioxide availability, low bacteria–solids ratio; mechanical damage or inhibition of the bacteria, inhibition of bacterial attachment, and the buildup of toxic leach products or other detrimental substances such as some flotation reagents. © 1993 John Wiley & Sons, Inc.
Step‐fortifications of nutrients in mammalian cell culture
Authors: Jo Eui‐Cheol , Kim Dong‐II , Moon Hong Mo 
Published: December 2004

AbstractA series of high‐density media for mammalian cell culture were developed by step‐fortifications of most nutrient components in RPMI‐1640 medium. Each medium constituting the series was constructed to meet in vitro cell growth limitations. Four different cell lines were cultivated in the media series, and their growth characteristics were observed. Maximum cell densities varied in the range of 0.4 to 1.3 × 107 cells/mL, depending on cell lines. Cell growth responses to each of the media series were analyzed in terms of cell density and cell mass. Step increases of cell mass in the range of 1.3 to 3.7 g/L were observed according to the step‐fortifications of nutrients. Also, the characteristics of each cell line were compared in terms of metabolic yields and specific productions of lactic acid and ammonium ion. The effect of step‐fortifications of nutrients on the production of monoclonal antibody was also examined. Apparent differences in metabolic characteristics among cell lines were observed. Experimental results suggested that the different cell sizes and metabolic characteristics of each cell line resulted in cell‐line–specific responses to the step‐fortifications. The significant influence of nutritional fortifications on high‐density culture of mammalian cells was evaluated. © 1993 John Wiley & Sons, Inc.
Design of a biomedical reactor for plasma low‐density lipoprotein removal
Authors: Shefer Samuel D. , Payne Richard G. , Langer Robert 
Published: December 2004

AbstractThe purpose of this study was to design a biomedical reactor that reduces plasma cholesterol when incorporated in an in vivo extracorporeal system. Phospholipase A2, immobilized onto Agarose beads and housed inside the bioreactor, modifies plasma low density lipoprotein (LDL) into a form that is rapidly removed from circulation. In a packed bed reactor, the enzymatic conversion of LDL to the modified form (with plasma taken from hypercholesterolemic New Zealand white rabbits) was relatively low, 25% ± 6 for a single pass of plasma through the reactor. An extended bed reactor, a hybrid of fluidized and packed bed reactors, was then developed to increase the conversion. This reactor displays a single pass conversion of 60% ± 5 under optimal flow conditions. An evaluation of the flow rate through the reactor indicates that the system is limited by external mass transfer when employed under in vivo conditions. In addition, this system requires blood separation before the enzyme modification, which complicates the circuit control. Therefore, a new system was designed for in vivo use with rabbits. The resulting design, called the plasma separator reactor (PSR), combines plasma separation and enzymatic conversion in a single chamber. The PSR has three advantages over other studied systems: improved external mass transfer conditions, easy controlability, and simple set‐up procedures. Single pass conversion reached 52% ± 12 in suboptimal flow under simulated in vivo conditions. This reactor was also tested in vivo with hypercholesterolemic New Zealand white rabbits. A continuous conversion of up to 80% ± 6 of rabbit plasma phospholipids was observed during 90 min of blood circulation (5 mL/min). The decrease in total plasma cholesterol reached a level of 60% of the initial value and was observed to be a function of the bioreactor enzyme activity. © 1993 John Wiley & Sons, Inc.
Optimization of 2,3‐butanediol production by Klebsiella oxytoca through oxygen transfer rate control
Authors: Beronio Peter B. , Tsao George T. 
Published: December 2004

AbstractProduction of 2,3‐butanediol by Klebsiella oxytoca is influenced by the degree of oxygen limitation. During batch culture studies, two phases of growth are observed: energy‐coupled growth, during which cell growth and oxygen supply are coupled; and, energy‐uncoupled growth, which arises when the degree of oxygen limitation reaches a critical value. Optimal 2,3‐butanediol productivity occurs during the energy‐coupled growth phase. In this article, a control system which maintains the batch culture at a constant level of oxygen limitation in the energy‐coupled growth regime has been designed. Control, which involves feedback control on the oxygen transfer coefficient, is achieved by continually increasing the partial pressure of oxygen in the feed gas, which in turn continually increases the oxygen transfer rate. Control has resulted in a balanced state of growth, a repression of ethanol formation, and an increase in 2,3‐butanediol productivity of 18%. © 1993 John Wiley & Sons, Inc.
An energetic model for oxygen‐limited metabolism
Authors: Beronio Peter B. , Tsao George T. 
Published: December 2004

AbstractMicrobial production of 2,3‐butanediol by Klebsiella oxytoca occurs under conditions of an oxygen limitation. The extent to which substrate is oxidized to 2,3‐butanediol and its coproducts, (acetic acid, acetoin, and ethanol) and the relative flow rates of substrate to energetic and biosynthetic pathways are controlled by the degree of oxygen limitation. Two energetic relationships which describe the response to an oxygen limitation have been derived. The first relationship describes the coupling between growth and energy production observed under oxygen‐limited conditions. This allows calculation of energetic parameters and modeling of the cell mass and substrate profiles in terms of the degree of oxygen limitation only. The second relationship describes the average degree of oxidation and the rate of the end‐product flow. The model has been tested with both batch and continuous culture. During these kinetic studies, two phases of growth have been observed: energy‐coupled growth, which was described above; and, energy‐uncoupled growth, which arises when the degree of oxygen limitation reaches a critical value. Optimal culture performance with respect to 2,3‐butanediol productivity occurs during energy‐coupled growth. © 1993 John Wiley & Sons, Inc.
Diffusivity of Cu2+ in calcium alginate gel beads: Recalculation
Authors: Lewandowski Z. , Roe F. 
Published: December 2004

AbstractCalculations of the diffusivity of Cu2+ in calcium alginate gel beads using the shrinking core model were checked by us. Corrected results are reported here. Diffusivity was still found to increase with increasing alginate concentration, but at a lower rate than reported in the cited paper. The diffusivity increased by a factor of 2 over the range of alginate concentrations studied rather than 10. The original data is included with sample calculations. © 1994 John Wiley & Sons, Inc.
Ammonia inhibition of hybridomas propagated in batch, fed‐batch, and continuous culture
Authors: Newland Mark , Kamal Mohammed Nazlee , Greenfield Paul F. , Nielsen Lars K. 
Published: December 2004

AbstractThe nature and temporal development of ammonia inhbition were investigated in batch, fed‐batch, and continuous cultures. Significant inhibition was observed when cells were inoculated in serum‐containing or chemically defined medium containing more than 2 mM of ammonia. In contrast, no inhibition was observed at greater than 10 mM when the ammonia concentration was gradually increased over the span of a batch culture by feeding ammonium chloride. Strong growth inhibition was observed after each of five step changes (2.8 → 3.7 → 4.0 → 4.9 → 7.7 → 13.5 mM) in continuous culture. Following a period of adaptation at each higher value, the viable cell density stabilized at a new lower value. The lowering in viable cell density was caused by an increase in specific death rate and a decreased cell yield on glucose, glutamine, and oxygen. Increased ammonia concentration had little or no effect on the steady‐state specific growth kinetics or specific antibody productivity. © 1994 John Wiley & Sons, Inc.