bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of physical and physicochemical pretreatments of wood for SCP production with Chaetomium cellulolyticum
Authors: Chahal D. S. , Moo‐Young M. , Vlach D. 
Published: December 2004

AbstractRelatively poor SCP production (4.2 mg/L h) was obtained using C. cellulolyticum and ground aspen wood treated with steam at atmospheric pressure for 1 h. The percentage of protein in the final product increased to 21.4% at a specific growth rate of 0.15 h−1 when the wood sample was treated with steam at a higher pressure (280 psig for 4 min) according to the "Stake" process. Alkali treatment (10% and 15% w/w at 121°C for 30 min), known to solubilize hemicelluloses and some of the lignin, gave intermediate results. More complete delignification of wood using NaClO2 increased the protein composition in the final product to 37.9%, at a specific growth rate of 0.19 h−1. Cellulose utilization was lowest (12.4%) in the case of the wood treated with steam at atmospheric pressure; it was higher at 75.3 and 78.5% for wood treated with NaOH at 10 and 15% w/w levels, respectively. The cellulose utilization was highest (90%) for wood treated with NaClO2.
Kinetic modeling of a multiple immobilized enzyme system. I. Development and testing of the model
Authors: Mercer D. G. , O'Driscoll K. F. 
Published: December 2004

AbstractA kinetic model for the reaction sequence catalyzed by coimmobilized invertase and glucose oxidase with a sucrose substrate in a tubular reactor has been developed. The computerized mathematical model employs and orthogonal collection technique for solving oxidase were coimmobilized in poly(2‐hydroxyethlmethacrylate) gels and used in a continuous flow packed‐bed tubular reactor system. In addition to describing the development of the kinetic model, this article compares experimentally determined reactor effluent concentrations for various sucrose feed solutions to those predicted by the model. Variations between experimental and predicted reactor effluent concentrations were found to be on the micromolar level for sucrose feed concentrations as low as 1.38mM.
γ‐Ray‐induced degradation of lignocellulosic materials
Authors: Han Y. W. , Timpa J. , Ciegler A. , Courtney J. , Curry W. F. , Lambremont E. N. 
Published: December 2004

AbstractLignocellulosic plant materials were treated with various swelling agents and exposed to γ radiation from 60Co or 137Cs. At dosages of 50 Mrad or above, lignocellulosic materials were extensively degraded and solubilized in water. Addition of water, NaOH, or H2SO4 to the substrate increased the degree of solubilization. Complete solubilization was achieved for samples of sugarcane bagasse, newspaper, cotton linters, cotton cloth, sawdust, and α‐cellulose powder. About 35% total sugar and 5% reducing sugar per dry weight of sugarcane bagasse could be obtained by this method. Most of the soluble carbohydrates seemed to be disaccharides or larger molecules and glucose degradation products. Solubilization of cellulose was dosage dependent and although the rate of solubilization was increased by adding alkali, released sugar was further decomposed by the alkali and by high dosage of radiation.
Kinetics of thermal denaturation of antithrombin III
Authors: Mitra G. , Schneider P. M. , Lundblad J. L. 
Published: December 2004

AbstractPurified antithrombin III (AT III), a single‐chain human plasma glycoprotein, molecular weight 58,000 daltons, and one of the major serine protease inhibitors, was heated in the 60–70°C range for inactivating possible contaminations by hepatitis B virus (HBV). Loss of inhibitory activity, unfolding of tertiary structure, and the rate of aggregate formation of AT III were monitored experimentally during heatig. Sucrose and sodium citrate were demonstrated to stabilize the protein. From the rate data the calculated activation energies (E) showed Etert. struct. < Ebiol. act. < Eaggreg. indicating the order (lower activation energy process first) in which heat causes these changes in the protein molecule. The activation energy corresponding to denaturation of HBV was estimated to be at least fourfold lower than that associated with the unfolding of the tertiary structure of the protein. Purified AT III, thus stabilized and pasteurized, should be therapeutically effective, and the risk for transmission of hepatitis B should be decreased significantly.
Effect of surface shear stress on the attachment of Pseudomonas fluorescens to stainless steel under defined flow conditions
Authors: Duddridge J. E. , Kent C. A. , Laws J. F. 
Published: December 2004

AbstractThe application of the radial‐flow growth chamber to the study of the initial stages of bacterial adhesion to surfaces under flowing conditions is reported. The adhesive properties of the bacterium Pseudomonas fluorescens (NCIB 9046) to stainless steel (type AISI 316) were found to be highly dependent on surface shear stress and the time and concentration of cells used in the incubation procedure. Maximum levels of adhesion occurred in zones of lowest surface shear stress, particularly less than 6–8 Nm−2. Adhesion was still noticeable at shear stresses even up to 130 Nm−2. Significant detachment of cells from a monolayer attached under static conditions was found to occur at surface shear stresses in excess of 10–12 Nm−2.
Production of surfactant by Arthrobacter paraffineus ATCC 19558
Authors: Duvnjak Z. , Cooper D. G. , Kosaric N. 
Published: December 2004

AbstractA. paraffineus ATCC 19558 grown in MMSM (modified mineral salts medium) containing hydrocarbon produced surfactant, with a maximum CMC−1 value obtained by using hexadecane as the carbon source. No activity of surface active agent in whole broth was observed when glucose was used in the MMSM instead of hexadecane. The biomass concentration obtained with glucose was about 40% of that obtained with hexadecane. Glucose (4%) in the medium contaning hexadecane caused a 27 and 21% decrease of biomass and surfactant concentrations, respectively. In the process of surfactant production, glucose can be used as a carbon source for growth, and hexadecane added later can serve for production of the surface active agent. The optimum temperature for production of surfactant is 27°C.
Strategies for penicillin fermentation in tower–loop reactors
Authors: König Burghard , Schügerl Karl , Seewald Christian 
Published: December 2004

AbstractSince it has not been possible to produce penicillin in tower–loop reactors with highly viscous filamentous molds ofPenicillium chrysogenumwhich are employed in stirred‐tank reactors, a new strategy has been developed to avoid the formation of this morphology and to use the pellet form of the fungi. When employing definite impeller speeds in the subculture in connection with definite inoculum amounts and substrate concentrations in the main culture (bubble column), it is possible to generate a suspension of isolated small pellets, which shows a low broth viscosity up to a sediment content of 45% over the entire fermentation time. Volumetric mass‐transfer coefficientskLasare by a factor of 4 to 5 higher in these pellet suspensions than in filamentous broths. It was easy to maintain the necessary oxygen supply for penicillin production in these pellet suspensions. Under these conditions the specific penicillin productivities were higher with regard to power input (up to 90%), biomass, and consumed substrate than in the stirred‐tank reactors with highly viscous filamentous morphology of the fungi. Under nonoptimized operating conditions the absolute penicillin production in the tower loop was 35% lower than in the stirred‐tank reactor due to lower possible biomass concentrations. The separation of the biomass, and therefore the penicillin recovery, is much simpler when employing pellets. It is shown how the particular mass transfer resistances at the gas/liquid and liquid/pellet interfaces and within the pellets change with the pellet diameter. There should be a particular pellet diameter at which penicillin productivity has its maximum. These investigations indicate that the use of tower‐loop reactors can, in the future, be an alternative for more economical penicillin production methods.
Properties of hydrocarbon‐in‐water emulsions stabilized by Acinetobacter RAG‐1 emulsan
Authors: Zosim Zinaida , Gutnick David , Rosenberg Eugene 
Published: December 2004

AbstractEmulsan is a polymeric extracellular emulsifying agent produced by Acinetobacter RAG‐1. Hydrocarbon‐in‐water emulsions (Vf of hydrocarbon of 0.01–0.10) were stabilized by small quantities of emulsan (0.02–0.2 mg/mL). Although both aliphatic and aromatic hydrocarbon emulsions were stabilized by emulsan, mixtures containing both aliphatics and aromatics were better substrates for emulsan than the individual hydrocarbon by themselves. The emulsan remained tightly bound to the hydrocarbon even after centrifugation as determined by (a) residual emulsan in the aqueous phase and (b) the fact that the resulting “cream” readily dispersed in water to reform stable emulsions. With hexadecane‐to‐emulsan weight ratio of 39 and 155, the noncoalescing oil droplets had average droplet diameters of 2.0 and 4.0 μm, respectively. Dialysis studies showed that the water‐soluble dye Rhodamine B adsorbed tightly to the interface of hexadecane–emulsan droplets although the dye did not bind to either hexadecane or emulsan alone. At saturating concentrations of dye, 2.2 μmol of dye were bound per mg emulsan.
Conversion of D‐xylose to ethanol by the yeast Pachysolen tannophilus
Authors: Slininger P. J. , Bothast R. J. , Van Cauwenberge J. E. , Kurtzman C. P. 
Published: December 2004

AbstractThe yeast Pachysolen tannophilus was found to be capable of converting D‐xylose to ethanol. Batch cultures initially containing 50 g/L D‐xylose yielded 0.34 g of ethanol per gram of pentose consumed. Aerobic conditions were required for cell growth but not for ethanol production. Both alcohol formation and growth were optimum when incubation temperature was 32°C, when pH was near 2.5, and when D‐xylose and ethanol concentrations did not exceed 50 and 20 g/L, respectively.
Fuel alcohol biosynthesis by Zymomonas anaerobia: Optimization studies
Authors: Kosaric N. , Ong S. L. , Duvnjak Z. 
Published: December 2004

AbstractThe optimum operating conditions for growth and ethanol production of Zymomonas anaerobia ATCC 29501 were established. The optimum pH range and temperature were found to be 5.0–6.0 and 35°C, respectively. Based on the results obtained from the temperature optimization study, an Arrhenius‐type temperature relationship for the specific growth rate was developed. The growth and ethanol production of this microbe also have been optimized in terms of concentrations of glucose, essential nutrients, and minerals. With optimum medium and operating conditions, an ethanol concentration of 96 g/L was obtained in 23 h. Both growth and ethanol yield coefficients in dependence on initial glucose concentrations were determined.
Diffusion resistance and enzyme activity decay in a pellet
Authors: Verhoff F. H. , Goldstein W. E. 
Published: December 2004

AbstractThe effective enzyme activity decay can be decreased by diffusion limitation in the immobilized pellet. Thiele modulus changes and/or poisoning of various enzyme forms are two phenomena which are influenced by diffusion limitation. This article considers these effects on enzyme decay as applied to glucose isomerase.
Kinetics of the acid precipitation of soya protein in a continuous‐flow tubular reactor
Authors: Virkar P. D. , Hoare M. , Chan M. Y. Y. , Dunnill P. 
Published: December 2004

AbstractThe acid precipitation of soya protein was studied in a continuous‐flow tubular reactor under conditions of turbulent flow. Preliminary batchwise experiments of a semiquantitative nature were also carried out on a bench‐scale reactor to better define the parameters affecting precipitate growth. The experiments indicated the dominant growth mechanism to be the aggregation of primary precipitate particles produced by the contacting of the protein and acid streams. The rate of particle growth was observed to rise with an increase in the protein concentration as well as with greater intensity of turbulence. The final mean particle size decreased with increased intensity of turbulence. A theoretical model was set up to simulate the growth of the precipitate particles.
The mechanism of thorium biosorption by Rhizopus arrhizus
Authors: Tsezos M. , Volesky B. 
Published: December 2004

AbstractInactive cells of Rhizopus arrhizus have been documented to exhibit a high thorium biosorptive uptake (170 mg/g) from aqueous solutions. The mechanism of thorium sequestering by this biomass type was investigated following the same method as for the uranium biosorption mechanism. The thorium sequestering mechanism appeared somewhat different from that of uranium. Experimental evidence is presented which indicates that, at optimum biosorption pH (4), thorium coordinates with the nitrogen of the chitin cell wall network and, in addition, more thorium is absorbed by the external section of the fungal cell wall. At pH 2 the overall thorium uptake is reduced. The kinetic study of thorium biosorption revealed a very rapid rate of uptake. Unlike uranium at optimum solution pH, Fe2+ and Zn2+ did not interfere significantly with the thorium biosorptive uptake capacity of R. arrhizus.
Immobilized enzymes: Electrokinetic effects on reaction rates in a porous medium
Authors: Ruckenstein Eli , Kalthod Dilip G. 
Published: December 2004

AbstractThe effect of the internal diffusion and electrical surface charge on the overall rate of a reaction catalyzed by an enzyme immobilized on a porous medium are examined. Effectiveness factors have been calculated which compare the global reaction rate to that existing in the absence of the internal diffusion and/or the electrical field. The surface charge, assumed to arise from the dissociation equilibria of the acidic and basic surface groups of the enzyme, generates an electrical double layer at the pore surface. The double‐layer potential is governed by the Poisson‐Boltzmann equation. It is shown that the diffusion potential can be characterized by a modulus which depends upon the surface reaction rate, the charges and diffusivities of the substrate and products, the ionic strength, and the pore dimensions. The flux of a charged species in the pore occurs under the influences of the concentration gradient and the electrical potential gradient. The governing equations are solved by an iterative numerical method. The effects of pH, enzyme concentration, and substrate concentration on the rates of two different hydrolysis reactions catalyzed by immobilized papain are examined. The release of H+ in one of the reactions causes the lowering of internal pH, and also a constancy of the internal pH when the external pH in creases beyond a certain value. The latter reaction also shows a maximum in the reaction rate with respect to enzyme concentration. The reaction not involving H+ as a product shows a maximum in the reaction rate with respect to external pH, but a monotonic increase in the reaction rate as the enzyme concentration increases.
Kinetics and activation energetics of death in Saccharomyces cerevisiae induced by sulfur dioxide
Authors: Anacleto J. , van Uden N. 
Published: December 2004

AbstractDeath of Saccharomyces cerevisiae induced by sulfur dioxide (K2S2O2 was used as the SO2 source) followed saturation kinetics. The enthalpy of activation of death was not affected by concentration over the range tested (5–150) mg/L of (K2S2O2 at pH 3.4) and averaged 3.6 × 104 cal/mol as compared with 8.5 × 104 cal/mol for ΔH‡ of thermal death. The entropy of activation of death was hyperbolic function of the sulfur dioxide concentration, extrapolated at zero concentration to ΔS0‡ = 36.8 cal mol−1 K−1 and tended to ΔΔSmax‡ = 13.2 cal mol−1 K−1 at saturating concentration, yielding a dis0sociation constant of 5.8 × 10−1 M sulfur dioxide. As was predicted from these results, In Kd (the specific rate of death induced by sulfur dioxide) was hyperbolic function of concentration under isothermic conditions and extrapolated toa finite value at zero concentration. The Arrhenuis plots and the ΔS± plot versus concentration revealed the occurrence of substrate inhabitation of the death effect at high concentrations (above 60 mg/L K2S2O2 at pH 3.4). A model is presented involving two types of receptor sites for sulfur dioxide on the cell surface, on directly connected with the death process, the other modulating its entropy of activation.
Anaerobic fluidized bed whey treatment
Authors: Boening Paul H. , Larsen Vidar F. 
Published: December 2004

AbstractAnaerobic treatment of moderate strength lactic casein why permeate [2000–7000 mg/L soluble chemical oxygen demand (SCOD)] is possible in fluidized bed reactors. Removal efficiencies up to 90% were obtained at organic removal rates of 7.7 kg SCOD M−3 day−1 and efficiencies of 70% were obtained at organic removal rates of 19.5 kg SCOD M−3 day−1, both at 35°C. A removal rate of 3.0 kg SCOD M−3 day−1 at 50% removal efficiency was obtained at 15°C. Nutrient requirements were much lower than for CSTR systems, and no supplemental nitrogen or phosphorus was required. Removal rates increased and removal efficiency decreased as the organic loading increased. Microorganism concentration increased with decreasing temperature, compensating for reduced reaction rates at lower temperatures.
Competition between two microbial populations in a nonmixed environment: Effect of cell random motility
Authors: Lauffenburger D. , Calcagno P. B. 
Published: December 2004

AbstractIn a nonmixed environment, bacterial population growth can be influenced significantly by cell motility properties as well as by growth kinetic properties. Therefore, in a situation of competition between two bacterial populations for a single chemical nutrient in a nonmixed environment, the outcome may depend upon the respective cell motility properties. In this article, the authors have presented a simple mathematical model for competitive growth of two randomly motile (i.e., possessing no chemotactic behavior) populations in a finite nonmixed region. An understanding of the behavior of this model should provide insight into the behavior of a number of common microbial competition problems. Analysis of this model yields the following results: (1) There may be as many as three possible non‐trivial steady‐state (or long‐time) configurations: when species 1 survives, species 2 dies out; when species 2 survives, species 1 dies out; and species 1 and species 2 coexist. (2) The coexistence state can exist even though one species possesses a smaller intrinsic growth rate constant at all nutrient concentrations, if that same species is sufficiently less motile than the other species. (3) In fact, the species with the smaller maximum specific growth rate may grow to a larger population than the other. (4) The possibility of coexistence can be decided essentially from the results for single population growth.
Fuel ethanol and high protein feed from corn and corn–whey mixtures in a farm‐scale plant
Authors: Gibbons William R. , Westby Carl A. 
Published: December 2004

AbstractDistiller's wet grain (DWG) and 95% ethanol were produced from corn in a farm‐scale process involving batch cooking–fermentation and continuous distillation–centrifugation. The energy balance was 2.26 and the cost was $1.86/gal (1981 cost). To improve the energy balance and reduce costs, various modifications were made in the plant. The first change, back‐end (after liquefaction) serial recycling of stillage supernatant at 20 and 40% strengths, produced beers with 0.2 and 0.4% (v/v) more ethanol, respectively, than without recycling. This increased the energy balance by 0.22–0.43 units and reduced costs by $0.07–$0.10/gal. The DWGs from back‐end recycling had increased fat. The second change, increasing the starch content from 17–19% to 27.5%, increased the ethanol in the beer from 10.5–14.9% at a cost saving of $0.41/gal. The energy balance increased by 1.08 units. No significant change was seen in DWG composition. The third change, using continuous cascade rather than batch fermentation, permitted batch‐levels of ethanol (10%) in the beer but only at low dilution rates. Both the cost and energy balance were decreased slightly. The DWG composition remained constant. The last change, replacing part of the corn and all of the tap water in the mash with whole whey and using Kluyveromyces fragilis instead of Saccharomyces cerevisiae during fermentation, resulted in an energy balance increase of 0.16 units and a $0.27/gal cost reduction. Here, 10% ethanolic beers were produced and the DWGs showed increased protein and fat. Recommendations for farm‐scale plants are provided.
Alkaline peroxide delignification of agricultural residues to enhance enzymatic saccharification
Authors: Gould J. Michael 
Published: December 2004

AbstractApproximately one‐half of the lignin and most of the hemicellulose present in agricultural residues such as wheat straw and corn stover are solubilized when the residue is treated at 25°C in an alkaline solution of hydrogen peroxide. The delignification reaction is most efficient when the ratio of hydrogen peroxide to substrate is at least 0.25 (w/w) and the pH is 11.5. The supernatant fraction from a given pretreatment, after addition of makeup peroxide and readjustment of the pH, can be recycled to treat at least six additional batches of substrate, resulting in a substantial concentration of hemicellulose and soluble lignin degradation products. Hydrolysis of the insoluble fraction with Trichoderma reesei cellulase after alkaline peroxide treatment yields glucose with almost 100% efficiency, based upon the cellulose content of the residue before treatment. These data indicate that alkaline peroxide pretreatment is a simple and efficient method for enhancing the enzymatic digestibility of lignocellulosic crop residues to levels approaching the theoretical maximum.
Mathematical modeling of diffusion and reaction in the hydrolysis of vegetable protein in an immobilized enzyme recycle reactor
Authors: Adu‐Amankwa B. , Constantinides A. 
Published: December 2004

AbstractExperimental investigation is by far the most effective approach for studying the behavior of physical systems. However, an enzymatic solubilization of vegetable protein is a complex combination of intrinsic problems, of which many are not easily adaptable to experimental investigation. Experimental designs to study enzyme vegetable protein reactions yield data which describe the extramembraneous activity of the immobilized enzyme. In a continuous recycle immobilized enzyme reactor, the microenvironment concentration of the substrate or product in the membrane phase, or the concentrations along the reactor axial length in the bulk phase are not discernible to the experimenter. However, the knowledge of such concentration profiles is important in weighing the significance of such factors as intermembrane diffusion, enzyme loading, wet membrane size, and the mode of operation of the reactor. The simulation of mathematical models, which describe the physical system within the constraints imposed, yields information which is vital to the understanding of the process occurring in the reactor. The kinetics and diffusion of an immobilized thermophilic Penicillium duponti enzyme at pH 3.4–3.7 and 50°C was modeled mathematically. The kinetic parameters were evaluated by fitting a model to experimental data using nonlinear regression analysis. Simulation profiles of the effects of reactor geometry, substrate concentration, membrane thickness, and enzyme leading on the hydrolysis rate are presented. From the profiles generated by the mathematical model, the best operational reactor strategy is recommended.