bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic studies of corn stover saccharification using sulphuric acid
Authors: Bhandari Nandan , Macdonald Douglas G. , Bakhshi Narendra N. 
Published: December 2004

AbstractThe kinetics of crystalline cellulose and hemicellulose hydrolysis in corn stover were studied with a nonisothermal technique. Reactions were arrested at temperatures between 160 and 240°C and product sugars were analyzed using a Bio‐Rad HPX‐85 liquid chromatographic column. A simple first‐order series reaction model was used for both cellulose and hemicellulose hydrolysis reactions. Kinetic parameters were obtained for three different sulphuric acid concentrations (0.49, 0.92, and 1.47 wt %). Activation energies remained constant over this acid concentration range but the preexponential factors showed an increase with acid concentration. Relationships were obtained between the preexponential factors and acid concentrations. Cellulose hydrolysis and glucose degradation reactions were observed to be of higher order with respect to acid concentration in comparison with the previous studies with other raw materials.
Cellobiose hydrolysis using Pichia etchellsii cells immobilized in calcium alginate
Authors: Jain D. , Ghose T. K. 
Published: December 2004

AbstractThe rate of celluose degradation, limited due to the inhibition by cellobiose, can be increased by the hydrolysis of cellobiose to glucose using immobilized β‐glucosidase. Production of β‐glucosidase in four yeasts was studied and a maximum activity of 1.22 IU/mg cells was obtained in cells of Pichia etchellsii when grown on 3% cellobiose as the sole carbon source. A study of the immobilization of β‐glucosidase containing cells of Pichia etchellsii on various solid supports was conducted and immobilization by entrapment in calcium alginate gel beads was found to be the most simple and efficient method. A retention of 96.5% of initial activity after ten sequential batch uses of the immobilized preparation was observed. The pH and temperature optima for free and immobilized cells were the same, i.e., 6.5 (0.05M Maleate buffer) and 50°C, respectively. Even though the temperature optimum was found to be 50°C, the enzyme exhibits a better thermal stability at 45°C. Beads stored at 4°C for six months retain 80% of their activity. Kinetic studies performed on free and immobilized cells shown that glucose is a noncompetitive product inhibitor.The immobilized preparation was found to be limited by pore diffusion but exhibited no film‐diffusion resistance during packed bed column indicated by a low dispersion number of 0.1348. A model for reaction with pore diffusion for a noncompetitive type of inhibited system was developed and applied to the cellobiose hydrolysis system. The rate of reaction with diffusional limitations was determined by using the model and effectiveness factors were calculated for different particle sizes. An effectiveness factor of 0.49 was obtained for a particle diameter of 2.5 mm. The modified rate expression using the effectiveness factor represented batch and packed bed reactor operation satisfactorily. The productivity in the packed bed column was found to fall rapidly with increase in conversion rate indicating that the operating conditions of the column would have to be a compromise between high conversion rates and reasonable productivity. A half‐life of over seven days was obtained at the operating temperature of 45°C in continuous operation of the packed bed reactor. However, the half‐life in the column was found to be greatly affected by temperature, increasing to over seventeen days at a temperature of 40°C and decreasing to less than two days at 50°C.
Production of 2,3‐butanediol from D‐xylose by Klebsiella oxytoca ATCC 8724
Authors: Jansen Norman B. , Flickinger Michael C. , Tsao George T. 
Published: December 2004

AbstractIt is known that 2,3‐butanediol is a potentially valuable chemical feedstock that can be produced from the sugars present in hemicellulose and celluose hydrolysates. Klebsiella oxytoca is able to ferment most pentoses, hexoses, and disaccharides. Butanediol appears to be a primary metabolite, excreted as a product of energy methabolism. The theoretical maximum yield of butanediol from monosaccharides is 0.50 g/g. This article describes the effects of pH, xylose concentration, and the oxygen transfer rate on the bioconversion of D‐xylose to 2,3‐butanediol. Product inhibition by butanediol is also examined. The most important variable affecting the kinetics of this system appears to be the oxygen transfer rate. A higher oxygen supply favors the formation of cell mass at the expense of butanediol. Decreasing the oxygen supply rate increases the butanediol yield, but decreases the overall conversion rate due to a lower cell concentration.
Immobilization of yeast pyridoxaminephosphate oxidase to halogenoacetyl polysaccharides
Authors: Tsuge H. , Okada T. 
Published: December 2004

AbstractPyridoxaminephosphate oxidase (EC 1.4.3.5, deaminating) that was partially purified about 40‐fold from dry baker's yeast was immobilized to iodo‐ and bromoacetyl polysaccharides. The most effective carrier was an iodoacetyl cellulose, to which almost complete activity of pyridoxine 5′‐phosphate oxidase was immobilized in 0.02M potassium phosphate buffer (pH 8.5) containing 2M ammonium sulfate at 4°C. The immobilized enzyme was more stable than the purified, soluble enzyme against heat and pH change. It was confirmed that N‐(5′‐phosphopyridoxyl)‐L‐serine was degradedly oxidized to pyridoxal 5′‐phosphate and L‐serine by the immobilized enzyme as comparable rate as pyridoxine 5′‐phosphate, whereas N‐(5′‐phosphopyridoxyl)‐D‐serine did not serve as substrate, as in the purified, soluble enzyme.
Estimation and control techniques for continuous culture fermentation processes
Authors: Gallegos Jaime Alvarez , Gallegos Joaquin Alvarez 
Published: December 2004

AbstractThis article presents results obtained when some modern estimation and control techniques are applied to a simulated fermentation process. The control structure uses a particular observer of the substrate concentration and assumes the biomass concentration is measurable. The overall structure has been tested for both external and parametric disturbances, with very good results.
Peroxidase‐catalyzed color removal from bleach plant effluent
Authors: Paice M. G. , Jurasek L. 
Published: December 2004

AbstractEffluent from the caustic extraction stage of a bleach plant is highly colored due to the presence of dissolved products from lignin chlorination and oxidation. Color removal from the effluent by hydrogen peroxide at neutral pH was catalyzed by addition of horseradish peroxidase. The catalysis with peroxidase (20 mg/L) was observed over a wide range of peroxide concentrations (0.1mM–500mM), but the largest effect was between 1mM and 100mM. The pH optimum for catalysis was around 5.0, while the basal rate of noncatalyzed peroxide color removal simply increased with pH within the range tested (3–10). Peroxidase catalysis at pH 7.6 reached a maximum at 40°C in 4 h assays with 10mM peroxide, and disappeared above 60°C. Compared with mycelial color removal by Coriolus versicolor, the rate of color removal by peroxide plus peroxidase was initially faster (first 4 h), but the extent of color removal after 48 h was higher with the fungal treatment. Further addition of peroxidase to the enzyme‐treated effluent did not produce additional catalysis. Thus, the peroxide/peroxidase system did not fully represent the metabolic route used by the fungus.
A dynamic mathematical model for microbial removal of pyritic sulfur from coal
Authors: Kargi Fikret , Weissman Jeffrey G. 
Published: December 2004

AbstractA dynamic mathematical model has been developed to describe microbial desulfurization of coal by Thiobacillus ferrooxidans. The model considers adsorption and desorption of cells on coal particles and microbial oxidation of pyritic sulfur on particle surfaces. The influence of certain parameters, such as microbial growth rate constants, adsorption‐descrption constants, pulp density, coal particle size, initial cell and solid phase substrate concentration on the maximum rate of pyritic sulfur removal, have been elucidated. The maximum rate of pyritic sulfur removal was strongly dependent upon the number of attached cells per coal particle. At sufficiently high initial cell concentrations, the surfaces of coal particles are nearly saturated by the cells and the maximum leaching rate is limited either by total external surface area of coal particles or by the concentration of pyritic sulfur in the coal phase. The maximum volumetric rate of pyritic sulfur removal (mg S/h cm3 mixture) increases with the pulp density of coal and reaches a saturation level at high pulp densities (e.g. 45%). The maximum rate also increases with decreasing particle diameter in a hyperbolic form. Increases in adsorption coefficient or decreases in the desorption coefficient also result in considerable improvements in this rate. The model can be applied to other systems consisting of suspended solid substrate particles in liquid medium with microbial oxidation occurring on the particle surfaces (e.g., bacterial ore leaching). The results obtained from this model are in good agreement with published experimental data on microbial desulfurization of coal and bacterial ore leaching.
Utilization of light for the assimilation of organic matter in Chlorella sp. VJ79
Authors: Lalucat J. , Imperial J. , Parés R. 
Published: December 2004

AbstractChlorella sp. strain VJ79 was isolated from a total heterotrophic count of a wastewater collector. It grows autotrophically, heterotrophically, and mixotrophically on a variety of organic substrates. Glucose and serine promote a mixotrophic growth from which the yield is higher than the sum of autotrophic and heterotrophic yields, but serine assimilation requires light. The interaction of glucose and light was studied in proliferating and nonproliferating cells by respirometry (IRGA and Warburg) and growth experiments. Glucose inhibits the photosynthetic CO2 fixation ten‐fold and modifies the pigmentary system as it does in heterotrophic cultures. Light inhibits glucose uptake and assimilation, but under mixotrophic conditions maximal utilization of glucose is obtained. Mutants defective in autotrophic growth were isolated by mutagenesis with nitrosoguanidine. They show a degenerated pigmentary system and a mixotrophic growth yield equal to that of the heterotrophic growth. The analysis of the mixotrophic system shows that light energy, dissipated during autotrophic growth, is used under mixotrophic conditions. From the increase in growth, the increase in photosynthetic efficiency can be calculated as ca. sixfold.
Mechanical control of foaming in a bubble column
Authors: Ohkawa Akira , Sakai Nobuyuki , Imai Hiroshi , Endoh Kazuo 
Published: December 2004

AbstractThis study was performed to evaluate the effects of the air sparge rate, working liquid volume, liquid feed rate onto the disk, and disk diameter on the foam‐breaking performance of foam‐breaking apparatus with a rotating disk (FARD) installed in the bubble column. Experimental results showed that the smaller the air sparge rate and working liquid volume were, and the larger the liquid feed rate and disk diameter, the lower the critical disk rotational speed required for reduced foam‐breaking. The presence of the effective ranges of the disk diameter and liquid feed rate for foam breaking was also confirmed. Furthermore, the quantitative predictions of the upper limits of the liquid feed rate, foam‐breaking regions, and the required foam‐breaking power were carried out, based on the results obtained above. Comparison of the FARD with two conventional mechanical foam‐breaking spray‐type apparati also demonstrated the highest level of the FARD in respect not only to foam‐breaking performance but also to power requirements.
Application of a statistical procedure for the control of yeast production
Authors: Kishimoto Michimasa , Sawano Toshihiro , Yoshida Toshiomi , Taguchi Hisaharu 
Published: December 2004

AbstractIn many cases of fermentation processes, it is difficult to measure all of the state variables needed to indicate the culture state and to predict state changes. We propose the use of time‐series data of measurable state variables instead of unmeasurable to describe the fermenatation process. We also employ a discrimination method of independent variables of regression analysis using statistical measures, PSS and AIC. These statistical procedure were applied to fed batch culture for yeast production under aerobic conditions, and the effectiveness was ascertained experimentally.
Enzyme immobilization in porous solid supports—penetration of immobilized enzyme
Authors: Do D. D. 
Published: December 2004

AbstractThe process of enzyme immobilization under the diffusion‐controlled regime (i.e., fast attachment of enzyme compared to its diffusion) is modeled and theoretically solved in this article. Simple and compact solutions for the penetration depth of immobilized enzyme and the bulk enzyme concentration versus time are presented. Furthermore, the conditions for the validity of our solutions are also given in this article so that researchers can discover when the theoretical solutions can be applied to their systems.
Hydrolysis of wheat straw hemicellulose with trifluoroacetic acid. Fermentation of xylose with Pachysolen tannophilus
Authors: Fanta G. F. , Abbott T. P. , Herman A. I. , Burr R. C. , Doane W. M. 
Published: December 2004

AbstractTreatment of wheat straw with 1N trifluoroacetic acid (TFA) for 7 h at reflux temperature yielded 23% xylose based upon initial straw weight. This corresponds to about an 80% xylose yield based on the xylan content of the hemicellulose. The cellulose component of wheat straw was largely unaffected, as evidenced by low glucose yields. Decomposition of xylose by prolonged refluxing (23 h) was minimal in 1N TFA compared to 1N HCl. Treatment of wheat straw with refluxing 1N TFA converts about 10% of the lignin initially present in straw into water‐soluble lignin fragments. Fermentation of the xylose‐rich wheat straw hydrolyzate to ethanol with Pachysolen tannophilus was comparable to the fermentation of reagent grade xylose, indicating that furfural and toxic lignin by‐products were not produced by 1N TFA in sufficient amounts to impair cell growth and ethanol production. Cellulase treatment of the wheat straw residue after TFA hydrolysis resulted in a 70–75% conversion of the cellulose into glucose.
Peptide synthesis in aqueous–organic solvent mixtures with α‐chymotrypsin immobilized to tresyl chloride‐activated agarose
Authors: Nilsson Kurt , Mosbach Klaus 
Published: December 2004

Abstractα–Chymotrypsin was immobilized with a high coupling yield (up to 80%) to tresyl chloride activated Sepharose CL‐4B.The immobilized enzyme was tested for its ability to synthesize soluble peptides from N‐acetylated amino acid esters as acyl donors and amino acid amides as acceptor amines in water–water‐miscible organic solvent mixtures. It was found that the yield of peptide increased with increasing concentration of organic cosolvent. Almost complete synthesis (97%) of Ac–Phe–Ala–NH2 was obtained from Ac–Phe–OMe using a sixfold excess of Ala–NH2. The rate of peptide formation in aqueous–organic solvent mixtures was good. Thus, 0.1M peptide was formed in less than 2 h in 50 vol% DMF with 0.1 mg immobilized chymotrypsin/mL reaction mixture. The immobilized enzyme distinguished between the L and D configurations of acceptor amino acid amides even in high concentration of nonaqueous component (90% 1,4‐butanediol). The effect of temperature was studied. It was found that both the yield of peptide and the stability of immobilized enzyme increased when the temperature was lowered. Experiments could be performed at subzero temperatures in the aqueous–organic solvent mixtures resulting in very high yield of peptide. After three weeks continuous operation at 4°C in 50% DMF, the immobilized enzyme retained 66%of its original synthetic activity. The activity of the immobilized enzyme was better conserved with a preparation made from agarose with a higher tresyl group content compared to a preparation made from a lower activated agarose, indicating that multiple point of attachment has a favorable effect on the stability of the enzyme in aqueous–organic solvent mixtures. The major advantage of using water‐miscible instead of water‐immiscible organic solvents to promote peptide syntheses appears to be the increased solubility of substrates and products, making continuous operation possible.
Feed component inhibition in ethanolic fermentation by Saccharomyces cerevisiae
Authors: Maiorella B. L. , Blanch H. W. , Wilke C. R. 
Published: December 2004

AbstractInhibition by secondary feed components can limit productivity and restrict process options for the production of ethanol by fermentation. New fermentation processes (such as vacuum or extractive fermentation), while selectively removing ethanol, can concentrate nonmetabolized feed components in the remaining broth. Stillage recycle to reduce stillage waste treatment results in the buildup of nonmetabolized feed components. Continuous culture experiments are presented establishing an inhibition order: CaCl2, (NH4)2×SO4 > NaCl, NH4Cl > KH2PO4 > xylose, MgCl2 > MgSO4 > KCl. Reduction of the water activity alone is not an adequate predictor of the variation in inhibitory concentration among the different components tested. As a general trend, specific ethanol productivity increases and cell production decreases as inhibitors are added at higher concentration. We postulate that these results can be interpreted in terms of an increase in energy requirements for cell maintenance under hypertonic (stressed) conditions. Ion and carbohydrate transport and specific toxic effects are reviewed as they relate to the postulated inhibition mechanism. Glycerol production increases under hypertonic conditions and glycerol is postulated to function as a nontoxic osmoregulator. Calcium was the most inhibitory component tested, causing an 80%decline in cell mass production at 0.23 mol Ca2+/L and calcium is present at substantial concentration in many carbohydrate sources. For a typical final cane molasses feed, stillage recycle must be limited to less than onethird of the feed rate; otherwise inhibitory effects will be observed.
Studies on on‐line bioreactor identification. I. Theory
Authors: Stephanopoulos Gregory , San Ka‐Yiu 
Published: December 2004

AbstractAn integrated approach is presented for the on‐line estimation of the state of a biochemical reactor from presently attainable real‐time measurements. Elemental and macroscopic balances are used for the determination of the total rate of growth and state‐of‐the‐art estimation techniques are subsequently employed for the elimination of process and measurement noises and the estimation of state variables and unknown culture parameters. The proposed approach is very flexible in that as new sensors become available they can be easily incorporated within the present framework to estimate new variables or improve the accuray of the old ones. The method does not require any model for the growth kinetics and is very successful in accurately estimating the above variables in the presence of intense noise and under both steady‐state and transient conditions. State estimates obtained by the presented method can be used for the development of adaptive optimal control schemes as well as for basic studies of the characteristic properties of microbial cultures.
Studies on on‐line bioreactor identification. IV. Utilization of pH measurements for product estimation
Authors: San Ka‐Yiu , Stephanopoulos Gregory 
Published: December 2004

AbstractRelationships between the total rate of biomass growth and the rate of ammonia addition to a fermentor for pH control are presented. These equations make use of the concept of reaction invariants and provide the additional information needed for bioreactor identification. They are especially useful when the RQ measurement is not sufficient for this purpose, such as when sensitivities arise with the measured values of the respiratory quotient or when fermentation products are formed. The cases of batch, fed‐batch and continuous fermentations, forming products with or without acidic/basic properties are considered. The derived relationships were successfully tested with nonbiological acid‐base continuous flow reaction systems and subsequently applied to the identification of the continuous yeast fermentation of glucose to ethanol. Results of these experimental studies are also presented.
Invertase immobilization via its carbohydrate moiety
Authors: Marek M. , Valentová O. , Káš J. 
Published: December 2004

AbstractAfter periodate oxidation of its glycosidic component, invertase was covalently bound onto three types of modified solid supports: glycidyl methacrylate, styrene–divinylbenzene copolymers, and bead cellulose. Direct reaction of the invertase aldehyde groups that were formed with amino groups of the support and use of the modified Ugi reaction have been employed as immobilization procedures. Apart from binding methods, the important effects of the buffer, support, conditions of periodate oxidation, and the length of the spacer on the activity of the enzyme conjugate have been investigated. Superior conjugate activity was obtained, via modified Ugi reaction, by the immobilization of a suitably oxidized invertase to a styrene–divinylbenzene copolymer having free amino groups.
Ease of removal of barnacles from various polymeric materials
Authors: Becka Ann , Loeb George 
Published: December 2004

AbstractThe forces required to remove living, fully attached barnacles from the surface of a number of polymeric solids were measured. The forces were related to the surface energy components of the materials. The results indicate a positive correlation between polymer surface energy and force required for barnacle removal. The nonpolar component of the surface energy was more closely related to the removal force than the polar component, although the polar component is significant. Adherence to some composite materials was greater than was consistent with the correlation for noncomposites.
Mixed populations of marine microalgae in continuous culture: Factors affecting species dominance and biomass productivity
Authors: Regan D. L. , Ivancic N. 
Published: December 2004

AbstractMarine microalgae were grown in multispecies continuous cultures. Under carbon dioxide limitation, blue–green algae dominated. Under nitrate and light limitation, species dominance depended on the initial conditions. When the inoculum consisted primarily of blue–green algae with smaller amounts of other species, blue–green algae and pennate diatoms dominated. When the inoculum consisted of equal amounts of all species, green flagellates and pennate diatoms dominated. Green flagellates and blue–green algae were incompatible and never shared dominance. When nutrient limitations were overcome, the productivity of seawater was increased 100‐fold before light limitation occurred. The productivity could be further increased by reducing photorespiration in the culture. The dilution rates studied (0.1, 0.2, and 0.4 day−1) had no effect on species dominance, nor did the higher dilution rates select for smaller cells. The maximum productivity occurred at a dilution rate of 0.2 day−1. Temperature had the greatest effect on species dominance, with green flagellates, pennate diatoms, and blue–green algae dominating at 20°C and only blue–green algae dominating at 35°C. The productivity at 35°C was lower than that at 20°C because of the lower solubility of carbon dioxide at higher temperatures. At 10% salinity, green flagellates and pennate diatoms dominated. The productivity at this salinity was 50% that obtained at the salinity of seawater (3.5%). At 25% salinity, only the green flagellate, Dunaliella salina, survived at a productivity of 1% that obtained at the salinity of seawater.