bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of solute hydrophobicity and phospholipid composition on permeability of composite membranes containing phospholipids
Authors: Sada Eizo , Katoh Shigeo , Terashima Masaaki , Yamana Shuichi , Ueyama Nobuhiko , Nagaya Mitsuru 
Published: December 2004

AbstractPermeabilities of several solutes through the composite membranes containing phospholipids have been measured. They were inversely proportional to the content of the phospholipids in the membrane. Both the permeability of solutes and the degree of permeability change around the phase transition temperature of the phospholipids for the hydrophobic solutes such as n‐butanol and salicylamide were larger than those for the hydrophilic solutes such as amino acids and pyridoxine. These results suggest thatthe permeation path of hydrophobic solutes is different from that of hydrophilic ones. The addition of phosphatidyl ethanolamine, phosphatidyl serine, or phosphatidic acid to the composite membrane influenced the solute permeability due to the introduced negative charge and/or the change in the molecular packing of phospholipid.
Biosorption of uranium and lead by Streptomyces longwoodensis
Authors: Friis N. , Myers‐Keith P. 
Published: December 2004

AbstractBiosorption of uranium and lead by lyophilized cells of Streptomyces longwoodensis was examined as a function of metal concentration, pH, cell concentration, and culture age. Cells harvested from the stationary growth phase exhibited an exceptionally high capacity for uranium (0.44 g U/g dry weight) at pH 5. Calculated values of the distribution coefficient and separation factor indicated a strong preference of the cell mass for uranyl ions over lead ions. The specific uranium uptake was similar for the cell wall and the cytoplasmic fraction. Uranium uptake was associated with an increase in hydrogen ion concentration, and phosphorus analysis of whole cells indicated a simple stoichiometric ratio between uranium uptake and phosphorus content. It is proposed that metal ions are bound to phosphodiester residues present both in the cell wall and cytoplasmic fractions. Based on this model, it was shown that uranium accumulation exhibits a maximum at pH 4.6 that is supported by experimental data from previous investigations.
Role of water activity in ethanol fermentations
Authors: Jones Rodney P. , Greenfield Paul F. 
Published: December 2004

AbstractA separate role for water activity in the conversion of sugars to ethanol by two strains of yeast is identified. During fermentation of both single and mixed sugar substrates, the water activity was shown to remain constant during the logarithmic growth phase. This is despite the changes in concentration of substrates and product, the constancy reflecting the fact that the greater influence of ethanol on the solution activity is counterbalanced, in the early stages of the fermentation, by its low yield. The end of the log phase of growth coincides with the start of a period of gradually decreasing water activity. For the more ethanol‐tolerant strain UQM66Y, growth was found to cease at a constant value of water activity while that for the less tolerant strain UQM70Y depended on both ethanol concentration and water activity. It is argued that water activity is a more appropriate variable than ethanol concentration for describing some of the nonspecific inhibitory effects apparent in ethanol fermentations. A straightforward method for the calculation of water activity during such fermentations based on the use of solution osmolality is presented.
The production of cellulase in a spouted bed fermentor using cells immobilized in biomass support particles
Authors: Webb C. , Fukuda H. , Atkinson B. 
Published: December 2004

AbstractContinuous cellulase production by Trichoderma viride QM 9123, immobilized in 6 mm diameter, spherical, stainless steel biomass support particles, has been achieved using a medium containing glucose as the main carbon source. Experiments were carried out in a 10‐L spouted bed fermentor. In this type of reactor‐recycled broth is used to create a jet at the base of a bed of particles, causing the particles to spout and circulate. During the circulation, particles pass through a region of high shear near the jet inlet. This effectively prevents a buildup of excess biomass and thus enables steady‐state conditions to be achieved during continuous operation. Continuous production of cellulase was achieved at significantly higher yield and productivity than in conventional systems. At a dilution rate of 0.15 h−1 (nominal washout rate for freely suspended cells is 0.012 h−1), the yield of cellulase on glucose was 31% higher than that measured during batch operation, while the volumetric productivity (31.5 FPA U/L· h) was 53% greater than in the batch system. The specific cellulase productivity of the immobilized cells was more than 3 times that of freely suspended cells, showing that diffusional limitations can be beneficial. This offers significant opportunity for the further development of biomass support particles and associated bioreactors.
Periodic optimization of continuous microbial growth processes
Authors: Abulesz E‐M , Lyberatos G. 
Published: December 2004

AbstractSteady‐state operation of continuous bioreactors is not necessarily the optimum type of operation. The method of π‐criterion is used in this work to determine whether periodic variation of the dilution rate can enhance the performance of continuous fermentation processes. It is found that the presence of time delay in the dynamic response of the chemostat renders a periodic operation of bioreactors, used for biomass production, superior to any steady‐state operation. Also, employing Williams' structured model it is shown that cycling improves the average protein productivity.
Enzymatic production of ethanol from cellulose using soluble cellulose acetate as an intermediate
Authors: Downing Kim M. , Ho Chester S. , Zabriskie D. W. 
Published: December 2004

AbstractA two‐stage process for the enzymatic conversion of cellulose to ethanol is proposed as an alternative to currently incomplete and relatively slow enzymatic conversion processes employing natural insoluble cellulose. This alternative approach is designed to promote faster and more complete conversion of cellulose to fermentable sugars through the use of a homogeneous enzymatic hydrolysis reaction. Cellulose is chemically dissolved in the first stage to form water‐soluble cellulose acetate (WSCA). The WSCA is then converted to ethanol in a simultaneous saccharification‐fermentation with Pestal‐otiopsis westerdijkii enzymes (containing cellulolytic and acetyl esterase components) and yeast.Water‐soluble cellulose acetate was successfully prepared from purified wood cellulose (Solka Floe) and chemical reagents. Enzyme pretreatment of WSCAto form metabolizable sugars was a necessary step in achieving practical conversion of WSCA to ethanol using yeast. The results showed that WSCA has a low enzyme requirement and a high convertibility to reducing sugars with enzymes from P. westerdijkii fungus. Pestalotiopsis westerdijkii enzymes were found to be superior to enzymes from Trichoderma viride in producing metabolizable glucose from WSCA. The yeast utilized 55–70% of the hydrolyzate sugars that were produced by P. westerrlijkii enzymes on WSCA and produced ethanol. The acetate that was liberated into solution by the action of acetyl esterase enzymes on WSCA was found to have a stimulatory effect on ethanol production in yeast. This is an important feature that can be used to advantage in manipulating the conversion to maximize the production of ethanol. Hence, the simultaneous saccharification‐fermentation of WSCA to ethanol using P. westerdijkii enzymes and yeast has features that are highly desirable for developing an economical cellulose conversion process.
Kinetics of ethanol fermentations in membrane cell recycle fermentors
Authors: Lee Chang Woo , Chang Ho Nam 
Published: December 2004

AbstractEthanol fermentation by yeast was carried out in a cell filtration recycle system with a hollow‐fiber membrane filter. Maximum biomass concentrations up to 210 g dry wt/L were obtained, but in normal operation concentrations they were between 100 and 150 g/L. The ethanol productivity using 14% glucose feed was 85 g/L h, with an ethanol concentration of 65 g/L and an ethanol yield of over 90%. The ethanol productivity and yeast growth rate decreased as the cell concentration increased beyond a certain level. The cell mass in the reactor was maintained by a proper manipulation of diluticn rate and bleed ratio depending on the growth rate.
Effects of cellobiose and glucose on cellulose hydrolysis by both growing and resting cells of Bacteroides cellulosolvens
Authors: Murray William D. 
Published: December 2004

AbstractThe cellulase system of Bacteroides cellulosolvens was subjected to both catabolite repression and feedback inhibition by cellobiose. Cellulose‐solubilizing activity was 50% inhibited at a cellobiose concentration of 2.6 g/L and completely inhibited by 12 g/L. Glucose at 12 g/L (the highest concentration tested) had no effect on cellulase activity. Supplementation of B. cellulosolvens cellulase with β‐glucosidase resulted in increased conversion of cellobiose to glucose; however, a constant cellobiose pool size of approximately 7 g/L was maintained.
Pullulan from peat hydrolyzate fermentation kinetics
Authors: Boa Jacques M. , LeDuy Anh 
Published: December 2004

AbstractThe Luedeking–Piret equation was used to fit the kinetic data of pullulan fermentations from peat hydrolyzate substrate. In batch mode, the kinetic parameters m, n, α, and β varied as a function of fermentation conditions: aeration rate, agitation speed, and temperature. In constant‐feed fed‐batch mode, the parameters Varied according to the feed rates. In peat hydrolyzate medium, the polysaccharide synthesis was strongly growth associated in batch and continuous fermentations but entirely growth associated in fedbatch fermentations. The fed‐batch mode of fermentation with an appropriate feed rate is more advantageous with respect to batch and continuous fermentations. Therefore, if the fermentation is started batchwise and then followed by fed‐batch mode at a constant feed rate, the overall polysaccharide productivity (g pullulan/L h) is significantly higher than those obtained with batch or continuous fermentations using the same total medium volume.
Kinetics of enzymatic lysis and disruption of yeast cells: I. Evaluation of two lytic systems with different properties
Authors: Hunter J. B. , Asenjo J. A. 
Published: December 2004

AbstractMany microorganisms produce enzymes which lyse the walls of yeasts, fungi, and bacteria. The proportions of different enzyme activities present in the lytic system, their action patterns, synergism, and dependence on inhibitors, constitute the activity profile of the lytic system. Taken together, the activity profile and process conditions for lysis determine the reaction rate and the distribution of products from lysis of any given type of cells. Kinetics of glucan hydrolysis, proteolysis, and lysis of brewer's yeast were compared for two extracellular yeast–lytic enzyme systems with different properties. The enzyme sources used were filtered culture broths from Cytophaga sp. NCIB 9497 grown in batch culture and from Oerskovia xanthineolytica LL‐G109, grown under carbon limitation in continuous culture. Rate and extent of cell hydrolysis, and the accumulation of soluble proteins, peptides, and carbohydrates from the lysed yeast cells, are discussed in terms of the activity profiles and potential applications of the two enzyme systems.
Kinetics of enzymatic lysis and disruption of yeast cells: II. A simple model of lysis kinetics
Authors: Hunter J. B. , Asenjo J. A. 
Published: December 2004

AbstractA simple two‐step model is proposed to describe the kinetics of the two lytic systems examined in the preceding article. The model predicts concentrations of yeast solids, soluble proteins, peptides, and carbohyrates. In the first reaction step, yeast cell mass is solubilized; in the second, the released protein can be hydrolyzed to peptides. Kinetics for both yeast lysis and the subsequent protein breakdown are based on Michaelis–Menten expressions. Terms have been included for competitive inhibition of yeast lysis by substances in the Cytophaga enzyme preparation, and for incomplete hydrolysis of cells by the Oerskovia enzyme system. Parameters have been independently determined for all reactions except Oerskovia proteolysis, where they were fit by a leastsquares method to data from model test runs. The model has been verified for yeast concentrations between 0.7 and 70 g/L yeast (dry basis) and 4–40% crude enzyme solution.
Evaluation of the effectiveness factor along immobilized enzyme fixed‐bed reactors: Design of a reactor with naringinase covalently immobilized into glycophase‐coated porous glass
Authors: Manjón A. , Iborra J. L. , Gómez J. L. , Gómez E. , Bastida J. , Bódalo A. 
Published: December 2004

AbstractA design equation is presented for packed‐bed reactors containing immobilized enzymes in spherical porous particles with internal diffusion effects and obeying reversible one‐intermediate Michaelis–Menten kinetics. The equation is also able to explain irreversible and competitive product inhibition kinetics. It allows the axial substrate profiles to be calculated and the dependence of the effectiveness factor along the reactor length to be continuously evaluated. The design equation was applied to explain the behavior of naringinase immobilized in Glycophase‐coated porous glass operating in a packed‐bed reactor and hydrolyzing both p‐nitrophenyl‐α‐L‐rhamnoside and naringin. The theoretically predicted results were found to fit well with experimentally measured values.
Mathematical analysis of two‐phase mass transfer in a batch reactor for the chemical transformation of a steroid
Authors: Pereira Vincent , Tigli Husevin , Gryte Carl C. 
Published: December 2004

AbstractA reactor is described for the conversion of the slightly water‐soluble steroid testosterone (T) to 4‐androstene‐3, 17‐dione (4‐AD) by enzyme in the presence of excess cofactor. Since the enzyme is subject to substrate inhibition, reaction rates are strong functions of aqueous substrate concentration. High concentrations of the substrate, testosterone, per unit reactor volume are maintained within poly(dimethylsiloxane) beads that are suspended in the aqueous enzyme solution. Mass transfer (controlled by bead size, polymer to water volume ratio, enzyme loading) is used to control the degree and rate of conversion. The reactor dynamics are predicted over a wide range of reaction conditions. The product steroid is recovered in the polymeric beads from the enzyme solution.
Affinity partitioning: Development of mathematical model describing behavior of biomolecules in aqueous two‐phase systems
Authors: Cordes A. , Flossdorf J. , Kula M.‐R. 
Published: December 2004

AbstractA mathematical model describing the affinity partitioning of macromolecules in aqueous two‐phase systems has been derived. The model was used to calculate binding parameters that were compared against values deter mined by means of ultracentrifugation and fluorescence titration. The mathematical model and its modifications were found to describe satisfactorily the partition behavior of macromolecules with differing numbers of binding sites. It could be shown that in solutions containing PEG the binding behavior of FDH is changed fundamentally. The dissociation constants of FDH with PEG‐blue in the presence and absence of PEG are different.
Feedback optimization of fed‐batch fermentation
Authors: Modak J. M. , Lim H. C. 
Published: December 2004

AbstractThe problem of feedback optimization of the feed rate for fed‐batch fermentation processes is formulated in the framework of singular control theory and switching hypersurfaces. Using four differential balance equations that describe a general class of fedbatch processes and a general objective function to be minimized, it is shown that under certain restrictions the feedback optimization of the feed rate can be realized as a nonlinear function of the state variables, such as the concentrations of cell mass, substrate and product, and the fermentor volume. The restrictions on the initial conditions, the fermentation kinetics and the objective function, that are needed for realization of the feedback optimization, are provided. Fed‐batch fermentation models of lysine and alcohol are used to construct switching curves and to illustrate the feedback optimization of the feed flow rates.
A fermentor for study of sauerkraut fermentation
Authors: Fleming H. P. , McFeeters R. F. , Humphries Ervin G. 
Published: December 2004

AbstractA fermentor was designed and constructed for study of the physical, microbiological, and chemical changes that occur during the sauerkraut fermentation. The fermentor has some essential features that include restriction in volume of the sauerkraut bed, construction of clear plastic to permit visual determination of liquid‐level changes as a result of gas entrapment within the sauerkraut bed, and a gas‐lift device for use in nitrogen purging of the fermenting brine. Fermentations exhibited two distinct stages, the first one gaseous and the second non‐gaseous. The gaseous stage was characterized by rapid CO2 and acid production due to growth by hetero‐fermentative lactic acid bacteria with resultant gas entrapment within the sauerkraut bed and a rise in liquid level. Also, rapid disappearance of fructose and rapid appearance of mannitol occurred during this stage. The nongaseous stage was characterized by growth of homo‐fermentative lactic acid bacteria with little or no CO2 production and a gradual increase in lactic acid until all fermentable sugars were metabolized. Nitrogen purging appeared to offer several potential advantages, including a means for brine circulation, removal of CO2 from the brine, and anaerobiosis to ensure retention of ascorbic acid, desirable color, and other oxygen‐sensitive traits in sauerkraut.
Treatment of leachate from a solid waste landfill site using a two‐stage anaerobic filter
Authors: Wu Y. C. , Hao O. J. , Ou K. C. , Scholze R. J. 
Published: December 2004

AbstractRaw leachate was treated using a two‐stage upflow anaerobic filter process. Leachate from a solid waste landfill site, which received both municipal and industrial wastes, contained high organic matter (17–21 g/L COD, 13–14 g/L BOD, and 3.5–4.6 g/L volatile acids), and low metal (Zn and Fe) concentrations. Depending on sampling time, leachate composition and characteristics varied considerably. At an organic loading up to 4 g COD/day2 media area, the BOD and COD removal percentages were 98 and 91%, respectively. The biofilters were also effective for metal removal. However, the filter effluent contained a high concentration of ammonia. System overloading was characterized by the accumulation of large quantities of volatile acids and by a now ratio of alkalinity/volatile acids, resulting in low COD removal and reduced gas production. Once the first filter was upset, the second stage could only partially respond to the volatile acids accumulated in the effluent of first filter.
High‐temperature alkaline α‐amylase from Bacillus iicheniformis TCRDC‐B13
Authors: Bajpai Pratima , Bajpai Pramod K. 
Published: December 2004

AbstractA bacterial strain, Bacillus licheniformis, has been isolated and identified which produces high‐temperature alkaline α‐amylase. Cultural conditions, such as types of carbon and nitrogen sources, temperature, pH, and time of reaction, have been optimized for production of α‐amylase in shake flask and fermenter. The enzyme produced was quite active even at 100°C; however, it showed optimum activity at 90°C. It exhibited optimum activity in the broad pH range 5.5–10. The effects of Na+ and Ca2+ ions on enzyme activity was also studied.
A study of methanol transport/uptake by a methanol‐utilizing bacteriumL3in a batch bioreactor
Authors: Agrawal Pramod , Flores Gary E. 
Published: December 2004

AbstractTwo novel, nitrogen‐limited and oxygen‐limited, perturbed transient experiments were performed to examine the presence of active transport of methanol and study the effect on methanol uptake by a methanol‐utilizing bacterium,L3, in a batch bioreactor. Transient limitations of both ammonium ions and O2in batch cultures were found to cause methanol leakages out of the cells, suggesting the presence of an active transport of methanol inL3. Such experimental results were used to indirectly estimate the intracellular levels of methanol during a batch growth ofL3. The results of our analysis indicate that the intracellular methanol level is high and show an increasing trend during the unbalanced phase, but falls to a constant low level in the balanced phase of a typical batch growth8ofL3. A simple modelling analysis suggests that a four‐parameter “pump‐and‐extrusion” model could be used to adequately describe the transport of methanol between the extra cellular and intracellular phases of batch cultures ofL3.
On‐line titration method for monitoring buffer capacity and total volatile fatty acid levels in anaerobic digesters
Authors: Powell G. E. , Archer D. B. 
Published: December 2004

AbstractThe construction and use of an automatic on‐line titration unit for routine or event‐ initiated monitoring of alkalinity, buffer capacity, and volatile fatty acid (VFA) levels is presented. Under computer control a sample of digester liquor is pumped into the titration vessel and weighed. A sequence of titration, sparging, and back‐titration operations are then initiated during which the pH and weight are recorded continuously and a titration curve constructed. From the curve, estimates of the alkalinity, buffer capacity to any desired pH endpoint, and total VFA levels are computed. The data is stored to disk and output as hard copy together with the titration curve itself. Monitoring and control of the titration apparatus is effected by a microcomputer via two analog input lines and eight digital output lines, respectively. The system is suitable for downloading to a small, inexpensive dedicated microprocessor‐based system. The apparatus is constructed from standard and widely available equipment and the titration sequence, being under software control, is fully adaptable to particular requirements. The use of this facility in the on‐line monitoring, control and optimization of the anaerobic digestion process is discussed.
Measurement of oxygen solubility in fermentation media: A colorimetric method
Authors: Slininger P. J. , Petroski R. J. , Bothast R. J. , Ladisch M. R. , Okos M. R. 
Published: December 2004

AbstractMethods of measuring oxygen solubility in culture media are scarce, and those available are tedious to apply. A simple colorimetric assay was developed and applied to the analysis of oxygen solubility during alcoholic fermentation. The method was based on the consumption of oxygen by glucose oxidase activity and the production of the pink quinone of syringaldazine by coupled peroxidase activity. Color formation at 526 nm progressed through an optimum that was a linear function of the oxygen added to the assay. Sensitivity was maximized by operating at pH 7 and limiting the medium sample volume added. Each assay took 10–15 min to prepare and react. Reaction time was minimized by using abundant glucose and enzyme concentrations. Data obtained by the assay developed showed good agreement with published oxygen solubilities in water and selected media at various temperatures. Subsequent analyses of fermentation broths indicated falling sugar concentration to be primarily responsible for increases in oxygen solubility during fermentation. For example, during fermentations started with 230 g/L xylose or glucose, oxygen solubility could increase by 41% due to sugar consumption alone. This procedure can provide the solubility data needed to accurately calibrate in‐line electronic probes for monitoring dissolved oxygen concentration during fermentation processes.