bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic modeling of the hydrolysis of sucrose by invertase
Authors: Bowski L. , Saini R. , Ryu D. Y. , Vieth W. R. 
Published: May 2005

AbstractThe kinetics of the enzymatic hydrolysis of sucrose by invertase have been examined, with particular emphasis on high substrate concentration. Initial rates of reaction were determined by following the production of glucose directly as a function of time over a wide range of substrate concentrations (0.04M to 2.06M). The resulting data reveal a reaction rate that increases gradually until the sucrose concentration reaches about 0.29M, after which the reaction velocity decreases with increasing sucrose concentration. Previous workers (e.g., Nelson and Schubert1) have reported a peak reaction velocity as determined by indirect polarimetric measurements of glucose, at a sucrose concentration of about 0.17M. These measurements, however, neglect the intermediate oligosaccharides formed by the transferase action of invertase,8–10 and assume equal amounts of glucose and fructose. According to Anderson et al.,10 these oligosaccharides interfere by producing an erroneously low reaction rate. Experimental results of this work confirm Anderson's observations, and show a further reaction rate increase of nearly 20% between sucrose concentrations of 0.177M and 0.285M under the same conditions of temperature, pH, and enzyme‐concentration.Effects of substrate diffusion, solution viscisity, water concentration, and substrate inhibition were experimentally studied and the results incorporated into a kinetic model that has proven satisfactory in modeling the experimental results. This model takes into account inhibition by primary substrate, with concentration of the secondary substrate water, as a rate limiting factor at sucrose concentrations greater than 0.285M.The effects of the mixing, in terms of volumetric power input, on the relation rate have been tested. Approximately 40‐fold increase in volumetric power input caused on increase in the reaction rate. These experiments have shown that bulk mass transfer is not a rate limiting factor under the experimental conditions.
Hydrocarbon fermentations using Candida lipolytica. I: Basic growth parameters for batch and continuous culture conditions
Authors: Moo‐Young M. , Shimizu T. , Whitworth D. A. 
Published: May 2005

AbstractCandida lipolytica (strain ATCC 8661) was grown on a simple defined medium with n‐dodecane as sole carbon source under batch and continuous fermentation conditions. The composition of cellular material recovered from the fermentations, the oxygen demand of the cells, and the effect of operating conditions on cell growth were evaluated experimentally. These basic data are presented and discussed.
Hydrocarbon fermentations using Candida lipolytica. II: A model for cell growth kinetics
Authors: Moo‐Young M. , Shimizu T. 
Published: May 2005

AbstractA mechanistic model is presented for the growth kinetics of a yeast grown by submerged aerobic fermentation using a liquid hydrocarbon as sole carbon source. The model is based on the assumption that cell growth is governed by the extent of probable cell attachment at the hydrocarbon oil‐droplet surfaces in a four‐phase dispersion. An analytical expression has been developed for the model. It is shown that for the case of relatively small oil droplets, the model predicts the present and previous experimental data for growth of yeasts (Candida species) in n‐alkane systems. The model is further examined for maximal growth in terms of substrate dilution rate and agitation power consumption for a continuous fermentation process.
Growth of microbes in an oil‐continuous environment
Authors: Coty V. F. , Gorring R. L. , Heilweil I. J. , Leavitt R. I. , Srinivasan S. 
Published: May 2005

AbstractThe growth of microorganisms in fermentations where oil had been maintained as the continuous phase was examined to determine whether advantage could be gained from the increased solubility of oxygen in hydrocarbon. Although cell concentrations were highest in the aqueous phase of oil‐continuous systems, due to the large oil fraction, productivities achieved per unit fermenter volume were generally equivalent to those obtained from water‐continuous systems. With the oil‐continuous emulsions, the power requirement for aeration and mixing was less, and phase reversal resulted in a threefold concentration of cells in the aqueous medium, thereby facilitating their recovery.
A pilot plant apparatus for continuous phased culture—some observations on oxygen usage by Candida utilis during the cell cycle
Authors: Dawson P. S. S. 
Published: May 2005

AbstractAn inexpensive scale‐up of the cyclone column apparatus (Can. J. Microbiol., 11, 893 (1965)) is described which is suitable for pilot plant studies on the 10 liter scale. Details of its construction and operation are given.Experimental with phased cultures of C. utilis growing in the equipment are reported during which studies of dissolved oxygen and oxygen uptake were made over the cell cycle. Changes in both oxygen parameters occurred during the cycle and were useful as monitors of the growth. Cell of C. utilis were found to be very sensitive to changes in oxygen supply during the early stages of the cell cycle.
Discussion on entrained droplets in fermenters used for the cultivation of single‐celled mircoorganisms
Authors: Hamer G. 
Published: May 2005

AbstractThe validity of regarding the liquid phase in vigorously agitated sparged fermenters during the cultivation of single‐celled aerobic microorganisms as essentially homogeneous is examined. Droplet formation from bursting bubbles and physical effects of the spray environment on single‐celled microorganisms are discussed. The implications of droplet removal from the head space of fermenters by collision with and drainage down the walls are considered, particularly factors concerned with wall growth above the liquid level in fermenters.
Parameter adaptation and control in a biochemical reactor
Authors: Weinrich S. D. , Lapidus L. 
Published: May 2005

AbstractA discrete optimally sensitive controller is developed which yields steady‐state feedback control of a three‐stage biochemical reactor system in spite of system parameter variations. A feedback law is implemented that estimates those variations which cause the output states to deviate from nominal, and adjusts the control policy in light of these variations.
A kinetic model for microbial growth on solid hydrocarbons
Authors: Chakravarty M. , Amin P. M. , Singh H. D. , Baruah J. N. , Iyengar M. S. 
Published: May 2005

AbstractA kinetic model has been presented to explain the growth of microorganism on solid hydrocarbons. The model is based on the assumption that metabolite produced by the growing cells helps the dissolution of the solid substrate in the aqueous medium. The linear behavior of the growth curve predicted by the model is verified experimentally.
Effect of mercury on algal growth rates
Authors: Hannan Patrick J. , Patouillet Constance 
Published: May 2005

AbstractIn experiments with one freshwater (Chlorella pyrenoidosa) and three marine organisms (Phaeodactylum tricornutum, Cyclotella nana, and Chaetoceros galvestonensis), mecury was more toxic than the other metals tested (silver, cadmium, lead, and copper); and its toxicity is comparatively irreversible. Growth was monitored by changes in fluorescence of the cultures over a 3‐day test period. The toxicity of the mercury varied inversely with the concentrations of nutrients present. Preliminary experiments indicate that mercury in the form of mercuric chloride is more than as dimethylmercury.
Continuous culture of Pseudomonas fluorescens with sodium maleate as a carbon source
Authors: Edwards Victor H. , Kinsella John E. , Sholiton David B. 
Published: May 2005

AbstractPseudomonas fluorescens (ATCC 11150) was grown in batch and continuous culture in minimal media with sodium maleate as growth‐limiting sole organic carbon source. Growth was followed by turbidity and dry weight measurements. Gross composition of washed cells (relative amounts of protein, lipid, RNA, and DNA) and the distribution of amino acids in protein hydrolyses of the cells were determined for cells grown in continuous culture at various dilution rates. Extracellular concentrations of the original carbon source and a number of metabolites were monitored by a total carbon analysis, ion exchange chromatography, and ultraviolet‐visible scans of cell‐free supernatants and chromatographic fractions, thereof.Substrate inhibition by maleate was a major factor in the growth kinetics of both batch and continuous cultures. Excessive maleate concentration caused instability in continuous cultures. By appropriate operation, much higher specific growth rates (0.305/hr) could ultimately be achieved in continuous culture compared to batch culture (0.174/hr). Adaptation was responsible for only part of the differences between batch and continuous cultures; the differing distribution of metabolites were also major factors.
A radial flow hollow fiber bioreactor for the large‐scale culture of mammalian cells
Authors: Tharakan John P. , Chau Pao C. 
Published: May 2005

AbstractA radial flow hollow fiber bioreactor has been developed that maximizes the utilization of fiber surface for cell growth while eliminating nutrient and metabolic gradients inherent in conventional hollow fiber cartridges. The reactor consists of a central flow distributor tube surrounded by an annular bed of hollow fibers. The central flow distributor tube ensures an axially uniform radial convective flow of nutrients across the fiber bed. Cells attach and proliferate on the outer surface of the fibers. The fibers are pretreated with polylysine to facilitate cell attachment and long‐term maintenance of tissuelike densities of cell mass. A mixture of air and CO2 is fed through the tube side of the hollow fibers, ensuring direct oxygenation of the cells and maintenance of pH. Spent medium diffuses across the cell layer into the tube side of the fibers and is convected away along with the spent gas stream. The bioreactor was run as a recycle reactor to permit maximum utilization of nutrient medium. A bioreactor with a membrane surface area of 1150 cm2 was developed and H1 cells were grown to a density of 7.3 × 106 cells/cm2.
Study of lignin biotransformation by Aspergillus fumigatus and white‐rot fungi using 14C‐labeled and unlabeled kraft lignins
Authors: Kadam Kiran L. , Drew Stephen W. 
Published: May 2005

AbstractThe biodegradation of lignin by fungi was studied in shake flasks using 14C‐labeled kraft lignin and in a deep‐tank fermentor using unlabeled kraft lignin. Among the fungi screened, A. fumigatus—isolated in our laboratories—was most potent in lignin biotransformation. Dialysis‐type fermentation, designed to study possible accumulation of low MW lignin‐derived products, showed no such accumulation. Recalcitrant carbohydrates like mi‐crocrystalline cellulose supported higher lignolytic activity than easily metabolized carbohydrates like cellobiose. An assay developed to distinguish between CO2 evolved from lignin and carbohydrate substrates demonstrated no stoichiometric correlation between the metabolism of the two cosubstrates. The submerged fermentations with unlabeled lignin are difficult to monitor since chemical assays do not give accurate and true results. Lignolytic efficiencies that allowed monitoring of such fermentations were defined. Degraded lignins were analyzed for structural modifications. A. fumigatus was clearly superior to C. versicolor in all aspects of lignin degradation; A. fumigatus brought about substantial demethoxylation and dehydroxylation, whereas C. versicolor degraded lignins closely resembled undegraded kraft lignin. There was a good agreement among the different indices of lignin degradation, namely, 14CO evolution, OCH3 loss, OH loss, and monomer and dimer yield after permanganate oxidation.
Protein separation by potential barrier chromatography
Authors: Ruckenstein E. , Lesins V. 
Published: May 2005

AbstractPotential barrier chromatography (PBC) is a liquid chromatographic method in which the adsorption and desorption of proteins are controlled by modifications of repulsive double‐layer and attractive van der Waals interactions between the proteins and the adsorbent through changes in mobile phase composition. In this review PBC is compared and contrasted to the more traditional chromatographic methods, namely, ion exchange, gel permeation, hydrophobic interaction, and affinity chromatography. The physical forces that underlie PBC (as well as the other methods) are discussed in terms of their effects on chromatographic behavior. Experimental results are presented to illustrate the use and simplicity of the method.
The adsorption of Thiobacillus ferrooxidans on coal surfaces
Authors: Bagdigian Robert M. , Myerson Allan S. 
Published: May 2005

AbstractThe adsorption of Thiobacillus ferrooxidans to coal surfaces has been studied. Adsorption experiments were conducted on coal samples from eight different Eastern coal fields. In all cases the adsorption process was at least 90% complete within the first two minutes following inoculation. The results of these experiments were used to test the validity of two proposed adsorption models. The first model assumes that bacterial adsorption follows second‐order irreversible kinetics of the second kind with respect to the concentration of bacteria and substratum surface area in the system. The second model allows for the contribution of reversible adsorption detected in desorption experiments. It was found that the combined reversible–irreversible model more accurately describes the initial stages of adsorption. Rate constants in both models were calculated for each coal sample. The relation of each of these constants to the pyrite concentration in coal is presented and the significance of these relations is discussed.Scanning electron micrographs of inoculated coal samples sho that Thiobacillus ferrooxidans selectively adsorb to exposed pyrite phases dispersed throughout the organic coal matrix. Preferential attachment was also observed along topographical faults in the caol surface. Mercury contact angle measurements on coal indicate that the selective adsorption of Thiobacillus ferrooxidans may be attributable to the lower surface free energy of pyrite relative to the organic coal matrix.
Alkali‐explosion pretreatment of straw and bagasse for enzymic hydrolysis
Authors: Puri V. P. , Pearce G. R. 
Published: May 2005

AbstractSugarcane bagasse and wheat straw were subjected to alkali treatment at 200°C for 5 min and at 3.45 MPa gas pressure (steam and nitrogen), followed by an explosive discharge through a defibrating nozzle, in an attempt to improve the rate and extent of digestibility. The treatment resulted in the solubilization of 40–45% of the components and in the production of a pulp that gave saccharification yields of 80 and 65% in 8 h for bagasse and wheat straw, respectively. By comparison, alkali steaming at 200°C (1.72 MPa) for 5 min gave saccharification yields of only 58 and 52% in 48 h. The increase in temperature from 140 to 200°C resulted in a gradual increase in in vitro organic matter digestibility (IVOMD) for both the substrates. Also, the extent of alkalinity during pretreatment appears to effect the reactivity of the final product towards enzymes. Pretreatment times ranging from 5 to 60 caused a progressive decline in the IVOMD of bagasse and wheat straw by the alkali explosion method and this was accompanied by a progressive decrease in pH values after explosion. In the alkali‐steaming method, pretreatment time had no apparent effect with either substrate. An analysis of the alkali‐exploded products showed that substantial amounts of hemicellulose and a small proportion of the lignin were solubilized. The percentage crystallinity of the cellulose did not alter in either substrate but there was a substantial reduction in the degree of polymerization. The superiority of the alkali‐explosion pretreatment is attributed to the efficacy of fiber separation and disintegration; this increases the surface area and reduces the degree of polymerization.
Direct evidence for a xylose metabolic pathway in Saccharomyces cerevisiae
Authors: Batt C. A. , Caryallo S. , Easson D. D. , Akedo M. , Sinskey A. J. 
Published: May 2005

AbstractXylose transport, xylose reductase, and xylitol dehydrogenase activities are demonstrated in Saccharomyces cerevisiae. The enzymes in the xylose catabolic pathway necessary for the conversion of xylose to xylulose are present, although S. cerevisiae cannot grow on xylose as a sole carbon source. Xylose transport is less efficient than glucose transport, and its rate is dependent upon aeration. Xylose reductase appears to be a xylose inducible enzyme and xylitol dehydrogenase activity is constitutive, although both are repressed by glucose. Both xylose reductase and xylitol dehydrogenase activities are five– to tenfold lower in S. cerevisiae as compared to Candida utilis. In vivo conversion of 14C‐xylose in S. cerevisiae is demonstrated and xylitol is detected, although no significant levels of any other 14C‐labeled metabolites (e. g., ethanol) are observed.
A mathematical model for cell separation technique of centrifugal elutriation
Authors: Barford J. P. 
Published: May 2005

AbstractA mathematical model for the cell separation technique of centrifugal elutriation is developed. The model simulates both steady and non‐steady‐state operation of the elutriator. The model can be used to predict the required set of flow rates of elutriating liquid necessary to fractionate a cell culture, the required time of sampling before steady state is achieved, and the range of cell size/cell density combinations contained in any fraction. The model predictions were verified experimentally. Variations in cell density and cell size due to the suspending environment have a significant effect on the accuracy (although not the trends) of the model predictions. Quantification of these variations will lead to significantly more accurate model predictions. An enhanced separation method was developed using the model, to yield finer separation of a cell culture than previously possible. The use of the centrifugal elutriator may now be given a firm theoretical basis, with the quality of separation understood in terms of the basic theory of operation.
Immobilization of trypsin on alginic acid–poly (glycidyl methacrylate) graft copolymer
Authors: Reddy C. Raghuram , Reddy C. Rami , Raghunath K. , Joseph K. Thomas 
Published: May 2005

AbstractTrypsin was immobilized onto alginic acid–poly(glycidyl methacrylate) graft copolymer (AAGMA). The resulting immobilized enzyme showed 65% of the soluble enzymatic activity. The temperature optimum was shifted by 5°C to a higher value. The pH optimum of immobilized enzyme has also been shifted by 0.5 units toward the alkaline side when compared to that of soluble enzyme. The pH stability and thermal stability are better than that of soluble enzyme.
Hexokinase activity as marker to assess time of harvest of foot‐and‐mouth disease virus in BHK21 Cl13 cell cultures
Authors: Suryanarayana V. V. S. , Banumathi N. , Rao B. U. 
Published: May 2005

AbstractHexokinase (B.C. 2.7.1.1) activity as a marker enzyme during FMD viral infection has been observed spectrophotometrically in a system coupled with glucose‐6‐phosphate dehydrogenase, in supernatants of BHK21Cl13 suspension as well as anchored cell culture at a minimum of 104 infective virus particles/ml. Specific activity increased with virus concentration in culture supernatants and abruptly decreased with a fall in virus titer, as has been noted by TCID/50,146 S concentration, and enzyme‐linked immunosorbent assay (ELISA) readings.
Immobilized phenylalanine hydroxylase through the SH groups
Authors: Koizumi Shinich , Takeuchi Tomio , Umezawa Hamao , Nagatsu Toshiharu 
Published: May 2005

AbstractPurified rat liver phenylalanine hydroxylase [L‐phenylalanine:tetrahydropteridine:oxygen oxidoreductase (4‐hydroxylating), EC 1.14.16.1] was immobilized with activated thiol‐Sepharose 4B via disulfide bond formation, which is expected to immobilize the enzyme in its activated form through the SH modification. This immobilized enzyme was more stable against thermal denaturation than the free enzyme. When tetrahydrobiopterin was used as the natural cofactor, the Km value for phenylalanine was decreased and that for the cofactor was increased. Constant conversion from phenylalanine to tyrosine was demonstrated continuously for over 8 h at 25°C.
Sugar cane bagasse as a possible source of fermentable carbohydrates. II. Optimization of the xylose isomerase reaction for isomerization of xylose as well as sugar cane bagasse hydrolyzate to xylulose in laboratory‐scale units
Authors: Olivier S. P. , du Toit P. J. 
Published: May 2005

AbstractBoth the forward and backward reactions of xylose isomerase (Sweetzyme Q) with xylose and glucose as substrates have been studied in terms of kinetics and thermodynamics. The relationship between the two reactions can thus be determined. Much attention has been given to the reaction with xylose as substrate. The optimal conditions of the xylose reaction in terms of pH, buffer, metal ions, substrate concentration, temperature, and ionic strength have been determined. These findings did not differ much from those reported for the glucose reaction. Equilibrium constants for the aldose to ketose conversion were more favorable in the case of glucose. The results obtained with continuous isomerization of xylose in columns packed with either Sweetzyme Q or Taka‐Sweet were very similar to those obtained from batch isomerization processes. Particle size had a definite effect on reaction rate, which indicates that diffusion limitations do occur with the immobilized enzyme particles. Heat stability of Sweetzyme Q was good with t1/2 of 118, 248, and 1200 h at 70, 55, and 40°C, respectively. A novel method for the separation of xylose–xylulose mixtures with water as eluant on a specially prepared Dowex 1 × 8 column was developed. This technique has the capability of producing pure xylulose for industrial or research applications. A writ for a patent regarding this technique is at present prepared.
Granulation of biomass in thermophilic upflow anaerobic sludge blanket reactors treating acidified wastewaters
Authors: Wiegant W. M. , de Man A. W. A. 
Published: May 2005

AbstractThe development of granular sludge in thermophilic (55°C) upflow anaerobic sludge blanket reactors was investigated. Acetate and a mixture of acetate and butyrate were used as substrates, serving as models for acidified waste‐waters. Granular sludge with either Methanothrix or Methanosarcina as the predominant acetate utilizing methanogen was cultivated by allowing the loading rate to increase whenever the acetate concentration in the effluent dropped below 200 and 700 mg COD/L, respectively. The highest methane generation rates, up to 162 kg CH4‐COD/m3 day, or 2.53 mole CH4/L day, were achieved at hydraulic retention times down to 21 min, with granules consisting of Methanothrix. The formation of Methanothrix granules did not depend on the type of seed material, nor on the addition of inert support particles. The growth of granules proceeded rapidly with adapted seed material, even when the reactors were inoculated with low concentrations. With mesophilic seed materials growth of granules took much longer. Thermophilic Methanothrix granules strongly resemble mesophilic granules of the “filamentous” type. Some factors governing the thermophilic granulation process are discussed.