bluuebunny/crossref_metadata_2025_split huggingface dataset:
Urokinase bound to fibrocollagenous tubes: An in vitro kinetic study
Authors: Senatore F. F. , Bernath F. R. 
Published: December 2004

AbstractUrokinase (UK) has been immobilized to the inner surfaces of fibrocollagenous tubes (FCT) in an attempt to develop a fibrinolytic biomaterial which may be suitable for use as a small diameter vascular prosthesis. The enzyme was bound by adsorption followed by glutaraldehyde crosslinking. An in virto kinetic study of immobilized urokinase was conducted by employing the tubular material as a flow through reactor operated in a batch recycle mode in which the esterolysis of the model substrate, N‐α‐acetyl‐L‐lysine methyl ester (ALME), was monitored as a function of substrate concentration, recycle flow rate, and temperature. Results were compared with data from the soluble enzyme reaction, which was conducted in the presence and absence of 10% swine skin gelatin, in order to identify the specific effects of a collagenous microenvironment. Observed rates for the UK‐FCT catalyzed reaction were observed to be dependent on recycle flow rates below 12 mL/min (Re = 107). Apparent Michaelis–Menten rate parameters were determined by a nonlinear search technique for two flow rates: one above the critical point for external diffusion effects (Re = 282) and one within the mass‐transfer‐limited region (Re = 71). When the latter data were corrected for external diffusion by applying the Graetz correlation for laminar flow in tubes to estimate themass transfer coefficient, the corrected Km of 6.45 ± 0.38 mM agreed very closely with the diffusion free parameter (i.e. 6.13 ± 0.63). Furthermore, this value was observed to be an order of magnitude higher than that of the soluble enzyme but approximately equal to the Km of the soluble enzyme in a 10% gelatin environment (8.13 ± 1.53 mM). It is postulated that the difference in kinetic parameters between soluble and collagen immobilized UK is due to an inherent interaction between collagen and enzyme rather than to mass transfer effects. Such aninteraction is supported by the effects of collagen on thermal stability and energy of activation.
Fermentation to ethanol of pentose‐containing spent sulphite liquor
Authors: Yu Shiyuan , Wayman Morris , Parekh Sarad K. 
Published: December 2004

AbstractEthanolic fermentation of spent sulphite liquor with ordinary bakers' yeast is incomplete because this yeast cannot ferment the pentose sugars in the liquor. This results in poor alcohol yields, and a residual effluent problem By using the yeast Candida shehatae (R) for fermentation of the spent sulphite liquor from a large Canadian alcohol‐producing sulphite pulp and paper mill, pentoses as well as hexoses were fermented nearly completely, alcohol yields were raised by 33%, and sugar removal increased by 46%. Inhibitors were removed prior to fermentation by steam stripping. Major benefits were obtained by careful recycling of this yeast, which was shown to be tolerant both of high sugar concentrations and high alcohol concentrations. When sugar concentrations over 250 g/L (glucose: xylose 70:30) were fermented, ethanol became an inhibitor when its concentration reached 90 g/L. However, when the ethanol was removed by low‐temperature vacuum distillation, fermentation continued and resulted in a yield of 0.50 g ethanol/g sugar consumed. Further improvement was achieved by combining enzyme saccharification of sugar oligomers with fermentation. This yeast is able to ferment both hexoses and pentoses simultaneously, efficiently, and rapidly. Present indications are that it is well suited to industrial operations wherever hexoses and pentoses are both to be fermented to ethanol, for example, in wood hydrolysates.
Deterministic interpretation of the temperature response of microbial growth
Authors: Fiolitakis Emmanuel , Grobbelaar Johan U. , Hegewald Eberhard , Soeder Carl J. 
Published: December 2004

AbstractA deterministic approximation of the thermal deactivation process is undertaken by structuring growth kinetics of cell populations on the activity level. Growth data of the green microalga Scenedesmus obliquus under forced periodic conditions of light intensity have been used for model verification. The model considers a straightforward extension of normal growth kinetics in such a way that different growth activities can be adjusted in the context of a thermal damage and repair mechanism. The nonlinear fitting of the measured response renders parameter values as a function of the light availability per unit biomass.
Selectivity enhancement of an Escherichia coli bacterial electrode using enzyme and transport inhibitors
Authors: Corcoran C. A. , Kobos R. K. 
Published: December 2004

AbstractThe feasibility of using specific enzyme and transport inhibitors to minimize the glutamine response of a potentiometric microbial sensor is demonstrated. The glutamine response of a bacterial electrode prepared with Escherichia coli as the biocatalyst in conjunction with an ammonia gas‐sensing electrode was greatly reduced by treating the electrode with the enzyme inhibitor 6‐diazo‐5‐oxo‐L‐norleucine (DONL) and the transport inhibitor γ‐L‐glutamylhydrazide. Each inhibitor effectively decreased glutamine response to a level sufficiently low to be considered negligible in clinical studies. Although the sensor ultimately recovered from the effects of a single exposure to an inhibitor, continuous exposure at an optimum concentration maintained a low response to glutamine. Furthermore, the treatment of the sensor with both inhibitors simultaneously resulted in a negligible response to glutamine of <1 mV, indicating that both inhibitors are necessary for optimum inhibition of glutamine response. This approach is promising as a means of enhancing the selectivity of microbial sensors.
Production of biosurfactants from sugar alcohols and vegetable oils catalyzed by lipases in a nonaqueous medium
Authors: Chopineau Joel , McCafferty Frank D. , Therisod Michel , Klibanov Alexander M. 
Published: December 2004

AbstractPorcine pancreatic and Chromobacterium viscosum lipases catalyze transesterification reactions between a number of sugar alcohols and various plant and animal oils in dry pyridine. The products of this process have been identified as primary monoesters of sugar alcohols and fatty acids. These enzymatically prepared sugar alcohol esters have been found to be excellent surfactants in terms of their ability to reduce interfacial and surface tensions and to stabilize emulsions.
Alginate as immobilization material: I. Correlation between chemical and physical properties of alginate gel beads
Authors: Martinsen A. , Skjåk‐Bræk G. , Smidsrød O. 
Published: December 2004

AbstractCalcium alginate gel beads were prepared from a range of well characterized alginates. The physical properties of beads depended strongly on the composition, sequential structure, and molecular size of the polymers. Beads with the highest mechanical strength, lowest shrinkage, best stability towards monovalent cations, and highest porosity were made from alginate with a content of L‐guluronic acid higher than 70% and an average length of the G‐blocks higher than 15. For these “high G” alginates the critical overlap intrinsic viscosities have been determined, and for molecular weight higher than 2.4 × 105, the gel strength was independent of the molecular weight.
An algorithm for operating a fed‐batch fermentor at optimum specific‐growth rate
Authors: Agrawal Pramod , Koshy George , Ramseier Michael 
Published: December 2004

AbstractAn algorithm for operating a fed‐batch fermentor at an optimum specific fermentation rate is proposed. It does not require on‐line measurement of nutrient concentration in the culture medium. An on‐line estimate of the specific fermentation rate is sufficient for implementation of this scheme. The algorithm is model independent and works well even with poor estimates of the product yields and the specific fermentation rate. Results of a detailed simulation study are presented for a simple case of optimization of cell‐mass production in a fed‐batch fermentor. The results clearly demonstrate the efficacy of this algorithm under a wide range of fermentation situations.
Effect of surface potential on consumption of charged substrates
Authors: Skowlund Christopher T. , Kirmse Dale W. 
Published: December 2004

AbstractDue to the surface charge inherent on all microorganism cell surfaces, the consumption of charged molecules by these microorganisms will be affected by the electrostatic interactions between the substrate and the cell surface. This article derives an equation that shows that these electrostatic interactions result in a change in the Monod half‐velocity constant. The resulting rate of consumption is affected and can be either higher or lower than the rate of consumption of an uncharged substrate molecule.
Study of gaseous substrate fermentations: Carbon monoxide conversion to acetate. 2. Continuous culture
Authors: Vega J. L. , Antorrena G. M. , Clausen E. C. , Gaddy J. L. 
Published: December 2004

AbstractThe fermentation of gaseous substrates such as CO, H2, and CO2 may be performed in a continuous stirred tank reactor, as well as the traditional batch reactor. In this article, the conversion of carbon monoxide by Peptostreptococcus productus is demonstrated in a stirred tank reactor under both mass transfer‐controlled and nonmass transfer‐controlled conditions. Utilizing a non‐steady‐state procedure, intrinsic rates are evaluated under non‐mass transfer‐controlled conditions in a time period of only 5–6 hours. A steady‐state procedure was used to evaluate CSTR performance under mass transfer‐controlled conditions. The mass transfer coefficient was calculated, followed by the development of a model to predict CSTR behavior for this gas phase substrate.
Effects of pH and added metabolites on bioconversions by immobilized non‐growing Clostridium acetobutylicum
Authors: Reardon Kenneth F. , Bailey James E. 
Published: December 2004

AbstractThe bioconversion activity of calcium alginate‐immobilized Clostridium acetobutylicum ATCC 824 was investigated in a continuous reactor system utilizing a defined feed medium which did not support cell growth. The changes in biocatalytic activity with time were studied at different pH values as well as when different metabolites (butyric, acetic, and acetoacetic acids) were present in the feed stream. Although the nongrowing cells were metabolically active, the product distribution was shifted from solvent production to acidogenesis. Overall activity losses occurred due to cell lysis, sporulation, and the effects of nitrogen level on macromolecular turnover. These effects were minimized under some operating conditions (e.g., pH 6), resulting in significantly longer productivity lifetimes.
Effect of induction temperature on the production of malaria antigens in recombinant E. coli
Authors: Okita B. , Arcuri E. , Turner K. , Sharr D. , Del Tito B. , Swanson J. , Shatzman A. , Zabriskie D. 
Published: December 2004

AbstractAs part of a process development campaign, studies have been conducted to determine the influence of induction temperature on the expression of two different malaria antigens, RN1 and RT2. Single‐step temperature inductions, in which growth at 32.0°C is followed by a shift in temperature to a desired setpoint, show that there exists an optimum duration and temperature of induction which is product specific. Between an induction temperature of 39.5 and 44.5°C RN1 yield is constant at ca. 0.20 g/g total soluble protein (TSP). RT2 yield approaches 0.20 g/g TSP only at elevated induction temperatures. The optimum temperature of induction for RN1 production is 39.5°C, whereas, that for RT2 production is 41.0°C. Above the optimum temperature of induction antigen concentration decreases owing to decreases in biomass. Furthermore, the maximum concentration of these two antigens differ by a factor of four. With increasing temperature of induction the extent of proteolysis of the products also appears to increase.
Performance of the anaerobic baffled reactor under steady‐state and shock loading conditions
Authors: Grobicki A. , Stuckey D. C. 
Published: December 2004

AbstractThe anaerobic baffled reactor (ABR) contains a granulated, mixed anaerobic culture segregated into compartments. Operation of four reactors under a range of hydraulic retention times showed that this novel reactor design offers highly efficient performance in the conversion of carbon in the feed stream to methane and carbon dioxide. The design parameter varied was the number of compartments. COD removal at 20 h retention time was routinely over 95% in all reactors, with low washout of biomass. Very high specific reaction rates were achievable (although with a loss of efficiency) at low biomass concentrations and high loading rates. In order to optimize volumetric reaction rates, a tradeoff has to be made between high biomass concentration, granule size, and the resulting mass transfer limitations. Formate is shown to be an important intermediate in the process under conditions of high loading.
Measurement of bacterial random motility and chemotaxis coefficients: II. Application of single‐cell‐based mathematical model
Authors: Ford Roseanne M. , Lauffenburger Douglas A. 
Published: December 2004

AbstractA quantitative description of bacterial chemotaxis is necessary for making predictions about the migratory behavior of bacterial populations in applications such as biofilm development, release of genetically engineered bacteria into the environment, and in situ bioremediation technologies. The bacterial chemotactic response is characterized by a mathematical model which relates individual cell properties such as swimming speed and tumbling frequency to population parameters, specifically the random motility coefficient and the chemotactic sensitivity coefficient. Our model includes a nonlinear dependence of the chemotactic velocity on the attractant gradient as well as a dependence of the random motility coefficient on the temporal and spatial attractant gradients, both of which previous analyses have neglected. As we will show, these aspects are critical for interpreting the results from experiments like those performed in the stopped‐flow diffusion chamber (SFDC) because the initial temporal and spatial gradients are very steep. Our analysis demonstrates that values for the random motility coefficient and chemotactic sensitivity coefficient can be obtained from experimental plots of net cell redistribution from initial conditions versus the square root of time. Values for these parameters are determined from experimental measurements of bacterial population distributions in the SFDC as described in the companion article. Using parameter values determined from independent experiments, μ = 1.1 ± 0.4 ± 10−5 cm2/s and χ0 = 8 ± 3 ± 10−5 cm2/s, excellent agreement is found between theoretically predicted bacterial density profiles and actual experimental profiles for Escherichia coli K12 responding to fucose over two orders of magnitude in initial attractant concentration. Thus, our model captures the concentration dependence of this behavioral response satisfactorily in terms of cell population parameters which are derived from individual cell properties and will therefore be useful for making predictions about the migratory behavior of bacterial populations in the environment.
Mass production of human epidermal growth factor using fed‐batch cultures of recombinant Escherichia coli
Authors: Shimizu Norio , Fukuzono Shinichi , Harada Yoshinori , Fujimori Kiyoshi , Gotoh Kenichi , Yamazaki Yoshio 
Published: December 2004

AbstractFed‐batch cultures of recombinant E. coli HB101 harboring expression plasmid pTRLBT1 or pTREBT1, with acetate concentration monitoring, are investigated to obtain high cell density and large amounts of human epidermal growth factor (hEGF). The expression plasmid pTRlBT1 contains a synthetic hEGF gene attached downstream of the N‐terminal fragment of the trp L gene preceded by the trp promoter. The expression plasmid pTREBT1 contains the same coding sequence attached downstream of the N‐terminal fragment of the trp E gene preceded by the trp promoter, trp L gene, and attenuator region. E. coli harboring pTREBT1 produces 0.56 mg/L hEGE and immediately degrades it. On the other hand E. coli harboring pTRLBT1 produces 6.8 mg/L hEGF and does not decompose it. Prominent inclusion bodies are observed in E. coli cells harboring pTRLBT1 using an election microscope. To Cultivate E. coli harboring pTRLBT1, a fed‐batch culture system, divided into a cell growth step and an hEGF production step, is carried out. The cells grow smoothly without acetate‐induced inhibition. Cell concentration and hEGF quantity reach the high values of 21 g/L and 60 mg/L, respectively.
Cleaning of inorganic membranes after whey and milk ultrafiltration
Authors: Daufin G. , Merin U. , Labbé J. P. , Quémerais A. , Kerhervé F. L. 
Published: December 2004

AbstractCleaning of an inorganic ultrafiltration membrane has been quantified through hydraulic, physicochemical, and spectroscopic (infrared and x‐photoelectron spectroscopy) analyses. An efficient cleaning sequence of nitric acid followed by sodium hypochlorite has been proposed for cleaning of defatted whey protein concentrate and milk ultrafiltration membranes. The influence of reversed sequence and time reduction are discussed together with the action of both cleaning chemicals. In spite of residual fouling left after every cleaning sequence studied, hydraulic cleanliness of the membrane was achieved, particularly after the standard procedure.
Hepatocyte culture on biodegradable polymeric substrates
Authors: Cima Linda G. , Ingber Donald E. , Vacanti Joseph P. , Langer Robert 
Published: December 2004

AbstractThe interactions of primary rat liver cells with biodegradable polymeric substrates were investigated in vitro to assess the suitability of the polymer materials for use in cell transplantation devices. The kinetics of cell adhesion to, and the growth and biochemical function of cells maintained on, films formed from poly (D,L‐lactic‐co‐glycolic acid, 88: 12) (PLGA) or from a 50/50 (w/w) blend of PLGA and poly (L‐lactic acid) (PLLA) were evaluated in comparison to two control substrates, matrigel coated or collagen‐coated polystyrene petri dishes. The rate of cell adhesion to both types of polymeric substrates was similar to the rate of adhesion to the collagen control substrate, but of the two polymers, only the blend was suitable for extended culture. Hepatocytes maintained on the polymer blend films showed retention of differentiated cell function as measured by the rate of albumin secretion–the rate of albumin secretion by cells on the films was the same as the rate for cells on matrigel and reached a level in the range of reported in vivo levels (140–160 μg/106 cells/24 h). In contrast, albumin secretion by hepatocytes maintained on collagen‐coated polystyrene culture dishes declined over five days to a level one third that of the initial level and one fifth that of cells maintained on the polymer blend films on day five. Such retention of differentiated cell function by hepatocytes in culture has previously been observed only when hepatocytes were cultured in the presence of exogenous extracellular matrix proteins or were cocultured with another cell type. In addition to retention of differentiated function, the cells maintained on the polymer blend films also displayed rates of DNA synthesis similar to controls maintained on collagen‐coated polystyrene, a substrate optimal for DNA synthesis.
Comments on the communication: On the calculation of shear rate and apparent viscosity in airlift and bubble column bioreactors
Authors: Allen D. Grant , Robinson Campbell W. 
Published: December 2004

AbstractThe determination of the shear rate in bubble column and airlift bioreactors is an important question from both the perspective of cell damage and the correlation of hydrodynamic parameters in non‐Newtonian fluids in these contractors. In the context of correlating hydrodynamic parameters in non‐Newtonian fluids, a common approach involves assuming that there exists an average shear rate in the column that is proportional to the superficial gas velocity. This average shear rate is then used to evaluate an effective viscosity of the non‐Newtonian fluid that is subsequently used to quantify the fluid's rheological behavior in correlation. Contrary to a recent communication, this report illustrates that this approach, which has mainly been applied to bubble columns, can also be applied to external loop airlift contractors, replacing the superficial gas velocity by the superficial gas velocity by the superficial gas velocity supplied to the riser of the contractor. This extension is based upon consideration of the relevant characteristic velocity in the active zone (i.e., the riser section) of the reactor.
A new biosensor for specific determination of sucrose using an oxidoreductase of Zymomonas mobilis and invertase
Authors: Park Je‐Kyun , Ro Hyeon‐Su , Kim Hak‐Sung 
Published: December 2004

AbstractA new biosensor for specific determination of sucrose was developed using an oxidoreductase of Zymomonas mobilis and invertase. Cells of Z. mobilis were permeabilized with toluene in order to utilize the enzymes of glucose–fructose oxidoreductase and gluconolactonase inside the intact cells. Permeabilized cells and invertase were coimmobilized in a gelatin membrane, and a whole cell enzyme electrode was constructed by fixing the membrane on a pH electrode. The production of hydrogen ion was detected using the biosensor‐connected microcomputer, and the concentration of sucrose was determined by using both the initial rate and the steady‐state methods. Optimum conditions for biosensor response were pH 6.2 and temperature 35°C. The effect of interfering compounds on the electrode response was investigated, and the interference by various sugars was eliminated by determining sucrose concentration using the steady‐state method. The biosensor developed is simple and reproducible, and the calibration curve for sucrose is linear up to 70 g/L.
A model for light‐limited continuous cultures: Growth, shading, and maintenance
Authors: Evers E. G. 
Published: December 2004

AbstractLight‐limited growth in continuous cultures of phototrophic organisms is modeled. It is assumed that light energy up‐take rate depends hyperbolically on light intensity and that the maintenance costs are proportional to biomass. Modeling the light distribution caused by shading within the vessel is necessary to explain the existence of steady state in light‐limited chemostats. The model fits well to experimental data from literature on light‐limited chemostats and turbidostats. Attention is given to the implications of the model for the estimation of the specific maintenance rate constant in light‐limited continuous cultures.
Use of coimmobilized biological systems to degrade toxic organic compounds
Authors: Lin Jian‐Er , Wang Henry Y. , Hickey Robert F. 
Published: December 2004

AbstractThe concept of coimmobilizing cell mass (and/or enzyme) and adsorbent in a hydrogel matrix for biodegradation of toxic organic chemicals was introduced. Under defined experimental conditions, the coimmobilized system using activated carbon and Phanerochaete chrysosporium was compared with nonimmobilized systems for the degradation of pentachlorophenol (PCP). It was demonstrated that the coimmobilized system degraded PCP more effectively than the nonimmobilized system. A solid substrate included in the coimmobilized system could support the biodegradation. Isolation of the degrading agents from a model interrupting microorganism by the coimmobilized capsule membrane reduced the interference on the biodegradation. In simulated contaminated soil extract and sand, the coimmobilized system also exhibited higher degradative ability and stability than the nonimmobilized systems.