bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth models of the continuous bacterial leaching of iron pyrite by Thiobacillus ferrooxidans
Authors: Chang Yun Chea , Myerson Allan S. 
Published: December 2004

AbstractThe leaching of iron pyrite by Thiobacillus ferrooxidans was studied in a continuous stirred tank reactor at a variety of dilution rates (0.012–0.22 h−1), pyrite surface areas (18–194 m2/L), and inlet soluble substrate (Fe2+) concentrations (0–3000 ppm). The bacterial leaching rate was found to increase with increasing pyrite surface area, dilution rate, and inlet Fe2+ concentration. The concentration of bacteria in solution was related to the concentration of bacteria attached to the pyrite surface by a Langmuir‐type adsorption‐desorption relation. Fitting the experimental data to this relation yielded a value for the area occupied per bacterium of 86 μm2. This result is consistent with the concept of preferential bacterial attachment of certain sites on the solid. A bacterial growth model was developed that included both bacterial growth in solution and growth of bacteria attached to the pyrite surface. The specific growth rate of the attached bacteria was calculated from this model and was found to increase with increasing solid dilution rate and to decrease with increasing pyrite surface area and soluble substance concentration. An explanation of these results based on an active‐inactive site mechanisms was also developed.
Hydrogen fluoride saccharification of wood: Lignin fluoride content, isolation of α‐D‐glucopyranosyl fluoride and posthydrolysis of reversion products
Authors: Hardt Haim , Lamport Derek T. A. 
Published: December 2004

AbstractWood chips from bigtooth aspen (Populus grandidentata Michx.) were saccharified by reaction with liquid hydrogen fluoride either anhydrous or containing up to 10% v/v water. The reaction products were separated into a solid lignin fraction and a water‐soluble saccharide fraction. The fluoride content of the lignin (determined after alkaline fusion) was initially about 1 mg/g wood, but was lowered to 0.1 mg/g wood by grinding and washing. Thus little or no chemical binding of fluoride to lignin occurred during hydrogen fluoride (HF) solvolysis. Analysis of the water‐soluble fraction by gel filtration on Biogel P2 columns showed a range of low‐molecular‐weight oligosaccharides and only 10–20% sugar monomers. Thus considerable reversion occurred during HF evacuation. Posthydrolysis conditions were optimized for these reversion products by varying temperature and acid concentration. Optimal conditions at 1 h were 140°C with 100mN sulfuric acid or 225mN Hydrofluoric acid resulting in monomer yields of > 90% for 0.5% sugar solutions and > 80% for 10% sugar solutions. After reaction of pure cellulose (Filter paper) with hydrogen fluoride in the absence of water, and terminating the reaction with calcium carbonate, the reaction intermediate α‐D‐glucopyranosylfluoride was isolated with a maximal yield of 0.2 g/g paper. Upon purification via paper chromatography glucosylfluoride was identified by its specific rotation and also by gas chromatography‐mass spectrometry of its tetra‐O‐trimethylsilyl derivative.
Ethanol production from Jerusalem artichoke tubers (Helianthus tuberosus) using Kluyveromyces marxianus and Saccharomyces rosei
Authors: Margaritis Argyrios , Bajpai Pratima 
Published: December 2004

AbstractThis article examines the potential of Jerusalem artichoke as a source for ethanol and single‐cell protein SCP. In addition, experimental results are presented on batch fermentation kinetics employing two strains of Kluyveromyces marxianus and one strain of Saccharomyces rosei grown on the extract derived from the tubers of Jerusalem artichoke. Of the three cultures examined, Kluyveromyces marxianus UCD (FST) 55–82 was found to be the best producer of ethanol grown in a simple medium at 35°C. The ethanol production was found to be growth‐associated having a μmax = 0.41. h−1 and the ethanol and biomass yields were determined to be Yp/s = 0.45 (88% of the theoretical) and Yx/s = 0.04 with 92% of the original sugars utilized. On the basis of carbohydrate yields of Jerusalem artichoke reported in the literature and these batch kinetic studies with K. maxxianus, the calculated ethanol yields were found to range from 1400 kg ethanol acre −1 yr−1to a maximum of 2700 kg ethanol acre −1 yr−1. The SCP yields for K. marxianus were calculated to range between 130 to 250 kg dry wt cell acre −1 yr−1. The potential for developing an integrated process to produce ethanol and SCP is also discussed.
The effects of temperature, inlet pollutant concentration, and microorganism concentration on the rate of aerobic biological treatment
Authors: Vavilin V. A. 
Published: December 2004

AbstractSystematic errors obtained in using traditional models of aerobic waste treatment processes are discussed. These errors are observed to arise due to the lack of matching of traditional models to experimental data in the case of broad variations of process parameters, for instance, organic loading. It is shown that the generalized models of waste treatment proposed earlier by the author permit these errors to be eliminated.
Cellulase production from immobilized growing cell composites prepared by radiation polymerization
Authors: Kumakura Minoru , Kaetsu Isao , Nisizawa Kazutosi 
Published: December 2004

AbstractThe cellulase production from immobilized Trichoderma reesei composites prepared by radiation polymerization at low temperature was studied. The production of cellulase from the cells irradiated by radiation was slightly retarded at the initial stage of the culture, but was immediately recovered. The production of cellulase resulting from the growth of the immobilized cells proceeds efficiently in the composite having a porous polymer matrix, in which the productivity of cellulase varied with the hydrophilicity, the shape of the composite, monomer, and cell concentration. It was found that cellulase produced by immobilized growing cell composites effectively hydrolyzed cellulosic wastes such as newspaper and chaff which are pretreated by irradiation and crushing.
A kinetic model for the hydrolysis and synthesis of maltose, isomaltose, and maltotriose by glucoamylase
Authors: Beschkov V. , Marc A. , Engasser J. M. 
Published: December 2004

AbstractKinetic results on the glucomylase‐catalysed hydrolysis of maltose and maltotriose, and glucose polymerization into maltose and isomaltose up to 450 g/L total sugar concentration are presented. Whereas the enzyme has a faster hydrolytic and synthetic activity on α‐(1→4) than on α‐(1→6) linkages, at equilibrium, on the contrary, the isomaltose level which represents 15% (w/w) of the total sugar concentration at the highest investigated concentrations is much higher than the corresponding maltose level. Under a wide range of initial conditions, experimental results are adequately described by a new kinetic model with simple first‐ and second‐order, or Michaelian‐type, rate expressions for the reversible hydrolysis of maltotriose, maltose, and isomaltose. The model also accounts for the inhibition of hydrolysis by glucose, but does not consider the concentration of water which, under the present conditions, was not found kinetically limiting.
The development of an immobilized lactate oxidase system for lactic acid analysis
Authors: Cannon John J. , Chen Li‐Fu , Flickinger Michael C. , Tsao George T. 
Published: December 2004

AbstractAn enzyme designated as lactate oxidase was purified from Acetobacter peroxydans by using the partition methods of separation. A DE‐52 cellulose column was used for the primary purification of lactate oxidase, and the purified enzyme was covalently bound to a porous cellulose bead matrix in which benzoquinone was used as the coupling reagent. The physicochemical properties of the native and immobilized enzymes were determined including molecular weight, cofactor requirements, and optimal reaction conditions. Lactate oxidase was shown not to be subject to product inhibition, and to require Mg2+ as a metal cofactor. Analysis of an immobilized lactate oxidase packed‐bed reactor indicated that this system may not be subject to internal diffusional limitations. Molecular oxygen appeared to be a cosubstrate of the enzyme, and a reaction mechanism was postulated to predict the kinetic behavior of the immobilized reactor system. Applications of the immobilized lactate oxidase reactor for the pulse‐flow analysis of lactic acid in whole milk and in a yeast fermentation system were considered.
Characterization of heterogeneous immobilized enzyme subpopulations using EPR spectroscopy
Authors: Clark Douglas S. , Bailey James E. 
Published: December 2004

AbstractDirect evidence was obtained for the existence of two distinct forms of active α‐chymotrypsin immobilized on CNBr‐activated Sepharose 4B. Electron paramagnetic resonance (EPR) spectra of five different spin‐labeled immobilized enzyme formulations in the presence of indole were all resolved into the same two spectral components. Both subpopulation spectra were approximately identified experimentally, and the subpopulation exhibiting greatly restricted spin‐label motion was shown also to be relatively inaccessible to solvent. Using overall specific activity data and subpopulation fractions from EPR spectral analysis, the specific activity of the more constricted immobilized enzyme active form was shown to be approximately 15 times smaller than that of the other class of immobilized enzyme molecules with an indole EPR spectrum similar to that of chymotrypsin in solution. Variations in overall specific activity of formulations with different loadings and different supports results entirely from changes in the proportions of the same two subpopulations of immobilized enzyme molecules.
A kinetic model for methanogenesis of acetic acid in a multireactor system
Authors: Bhadra Amit , Mukhopadhyay S. N. , Ghose T. K. 
Published: December 2004

AbstractBioconversion of acetic acid to methane by a crude culture of methanogens in a continuous multireactor system was investigated. Culture of methanogens was drawn from an active cow‐dung digester (12 days) and was grown in a semisynthetic medium (pH 6.3, 37°C) with acetic acid as the sole carbon source. The solubilities of CO2, HCO3−, and CO32− increased with the rise in pH and exercised considerable influence on the gas composition. Various mechanisms for methanogenesis of acetic acid based on the available pathways were considered. Experimental data were compared with these mechanisms, the best fit was determined, and the corresponding rate expression was identified. This mechanism predicted that, of the total methane produced, 72%;comes from acetic acid directly and 28%;via the CO2 reduction route.
Bioengineering of photosynthetic membranes. Requirement of magnesium for the conversion of chlorophyllide a to chlorophyll a during the greening of etiochloroplasts in vitro
Authors: Daniell Henry , Rebeiz Constantin A. 
Published: December 2004

AbstractThe massive conversion of δ‐aminolevulinic acid (ALA) to protochlorophyllide (Pchlide) and the massive conversion of chlorophyllide a (Chlide a) to chlorophyll a (Chl a) are two essential conditions for the ALA‐dependent assembly of photosynthetic membranes in vitro. In this work, we describe the development of a cell‐free system capable of the forementioned biosynthetic activities at rates higher than in vivo, for the first 2 h of dark‐incubation. The cell‐free system consisted of (1) etiochloroplasts prepared from kinetin and gibberellic‐acid‐pretreated cucumber cotyledons, and (2) cofactors and additives described elsewhere and which are needed for the massive conversion of ALA to Pchlide, (3) high concentrations of ATP, MgCl2, and an isoprenol alcohol such as phytol, were required for the massive conversion of Chlide a to Chl a. An absolute and novel requirement of Mg2+ for the conversion of Chlide a to Chl a was also demonstrated. In addition to the role of phytol as a substrate for the conversion of Chlide a to Chl a, the data suggested that this alcohol may also be involved in the regulation of the reactions between ALA and Pchlide. It is proposed that during greening, the conversion of Chlide a to Chl a may follow different biosynthetic rates, having different substrate and cofactor requirements, depending on the stage of plastid development.
Plasmid stability in budding yeast populations: Steady‐state growth with selection pressure
Authors: Hjortso Martin A. , Bailey James E. 
Published: December 2004

AbstractPlasmid gene product accumulation in a cell population depends on the fraction of plasmid‐containing cells and the distribution of single‐cell plasmid content. These important population properties have been related to plasmid replication regulation and kinetics and to plasmid segregation rules at the single‐cell level using population balance mathematical models. Budding yeast populations are considered in detail because of the practical potential of yeast host–vector systems and because of the model complications introduced by the asymmetric division pattern observed for Saccharomyces cerevisiae at all but the largest growth rates. Solutions are presented for several different reasonable models of plasmid replication and segregation. The results offer potential for identification of important qualitative features of yeast plasmid replication and of model parameter values from average and segregated experimental data on yeast populations.
Enzymatic hydrolysis of sodium‐hydroxide‐pretreated sallow in an ultrafiltration membrane reactor
Authors: Ohlson Ingrid , Trägårdh Gun , Hahn‐Hägerdal Bärbel 
Published: December 2004

AbstractAn ultrafiltration membrane reactor was used to investigate the recovery of biocatalysts during enzymatic hydrolysis of pretreated sallow. Product inhibition could be eliminated by continuous removal of products through the ultrafiltration membrane, thus retaining the macromolecular substrate and enzymes. In this way, the degree of conversion was improved from 40% in a batch hydrolysis to 95% (within 20 h), and the initial hydrolysis rate was increased up to seven times. The recovery studies were focused on mechanical deactivation and irreversible adsorption on to the nonconvertible fraction of the substrate. Cellulase deactivation during mechanical agitation was not significant, and the loss of activity was attributed mainly to strong adsorption of the enzymes onto undigested material. This process was studied in semicontinuous hydrolyses, where fresh substrate was added intermittently. The amount of reducing sugars produced in this experiment was 25.7 g/g enzyme, compared to 4.7 g/g enzyme in a batch hydrolysis.
Invertase covalent grafting onto corn stover
Authors: Monsan P. , Combes D. , Alemzadeh I. 
Published: December 2004

AbstractThe covalent coupling of an invertase from baker's yeast onto an agricultural by‐product, corn grits, has been developed. The optimal conditions for each step of the chemical modification of the support have been determined: oxidation with sodium metaperiodate, amination with ethylenediamine, reduction with sodium cyanoborohydride, and activation with glutaraldehyde. Activities up to 7.2 × 104 μmol reducing sugars produced/min g support could thus be achieved. Invertase coupling onto corn grits yields a derivative with a 25 times higher activity than when coupling this enzyme onto porous silica. The operational stability of invertase immobilized onto corn stover was found to be very high, with a half‐life of up to 365 days at 40°C when using a 2M sucrose solution as substrate. This immobilization method could be easily scaled up to the preparation of 10 kg of invertase derivative.
DNA immobilized onto an acyl‐azide derivative of collagen membranes for use as immunoadsorbent
Authors: El Habib Raphaelle , Coulet Pierre R. , Sanhadji Kamel , Gautheron Danielle C. , Laville Maurice , Traeger J. 
Published: December 2004

AbstractSingle‐ and double‐stranded DNA were immobilized on films of highly polymerized collagen by a covalent process. The coupling was efficient at an acidic pH with an optimum at pH 5, while preventing the collagen film from any damage. In addition, no leakage occurred, so it was possible to use this DNA‐coated collagen film as an immunoadsorbent. Therefore the findings reported here suggest that the acyl‐azide procedure is also suitable for DNA binding on a proteinic support. Promising results in specific clearance of DNA antibodies were obtained in vitro.
Microbial oxidation of dibenzothiophene by the thermophilic organism Sulfolobus acidocaldarius
Authors: Kargi Fikret , Robinson James M. 
Published: December 2004

AbstractThe refractory organic sulfur compound dibenzothiophene (DBT) has been oxidized by the thermophilic, sulfur oxidizing organism Sulfolobus acidocaldarius. Sulfate ions were released into the medium as the oxidation product. The kinetics of this oxidation have been investigated on the basis of sulfate released as a result of oxidation. Dibenzothiophene was found to be inhibitory to the organisms for initial concentrations over 500 mg/L. The organism may prove to be capable of oxidizing thiophene compounds present in oil refinery wastewater, coal, and crude oil.
Mechanisms for the acoustic conditioning of protein precipitates to improve their separation by centrifugation
Authors: Bell D. J. , Dunnill P. 
Published: December 2004

AbstractA theoretical description of a low‐frequency, dual‐source acoustic treatment of protein precipitates is presented. Two mechanisms for the potential improvement of the centrifugal separation of precipitates are proposed. They are acoustic aggregation, which causes an increase in particle size, and aggregate deformation, which results in an increase in aggregate density. Experiments with isoelectric soya protein precipitate indicated that the extent of ageing prior to acoustic conditioning is important. Support for both aggregation and dewatering was found and a maximum increases in the particle settling velocity of 20% was observed.
The influence of fluid mixing upon respiratory patterns for extended growth of a methylotroph in an air‐lift fermenter
Authors: Fields Peter R. , Slater Nigel K. H. 
Published: December 2004

AbstractThe influence of methanol dispersion and fluid mixing upon respiratory patterns observed during unlimited fedbatch growth of the methylotrophic bacterium Methylophilus methylotrophus has been investigated. A concentric tube air‐lift fermenter was employed for which the mixing and fluid circulation patterns have been well characterized. Respiratory quotients showed a marked dependence upon the position in the vessel at which methanol was injected, the volumetric rate of such methanol addition, the fluid circulation time, and the local mixing behavior; the latter two factors of which are both determined by the air throughput. Such variations are discussed on the basis of simple mixing concepts and observations of fluid dispersion.
Improved biocatalyst effectiveness by controlled immobilization of enzymes
Authors: Borchert A. , Buchholz K. 
Published: December 2004

AbstractNonuniform enzyme distributions can be obtained by kinetic control of the immobilization process. Such heterogeneous biocatalysts exhibit higher effectiveness compared to conventional immobilization procedures, when the mass transfer of substrates or products is limiting. Model calculations provide some insight into the relative weight of the immobilization parameters with respect to optimal control of the enzyme distribution. Experimental results and model calculations show that considerably improved effectiveness of biocatalysts can be obtained. The role of external mass transfer is emphasized.
Ethanol fermentation in a continuous tower fermentor
Authors: Jones Stephen T. , Korus Roger A. , Admassu Wudneh , Heimsch Richard C. 
Published: December 2004

AbstractA mutant of Saccharomyces cerevisiae, which forms large, multicellular flocs in liquid culture, rapidly fermented media containing high concentrations of glucose (100–180 g/L) in a continuous nonaerated tower fermentor at 30°C. The fermentor operated continuously for seven months. Batch and tower fermentor data were fitted to a kinetic model incorporating linear ethanol inhibition and Monod dependence on glucose. Conversion, ethanol yield, and ethanol productivity were related to the apparent fermentation time for initial glucose concentrations of 130 and 180 g/L. Productivities of 8–12 g ethanol/L h were achieved through the yeast bed giving conversions exceeding 90% of the theoretical yield.
Continuous growth kinetics of Candida utilis in pineapple cannery effluent
Authors: Prior B. A. 
Published: December 2004

AbstractCandida utilis was grown on a pineapple cannery effluent as the sole carbon and energy source in a chemostat at dilution rates between 0.10 and 0.62 h−1 to determine the growth kinetics. The principal sugars in the effluent were sucrose, glucose, and fructose. The cell yield coefficient on carbohydrate varied with dilution rate and a maximum value of 0.63 was observed at a dilution rate of 0.33 h−1. The steady‐state concentrations of carbohydrate, reducing sugar, and chemical oxygen demand (COD) appeared to follow Monod saturation kinetics with increasing dilution rate, although none of the measured parameters represented a pure substrate. The maximum specific growth rate and reducing sugar saturation constant were 0.64 h−1 and 0.060 g/L, respectively. A maximum cell mass productivity of 2.3 g/L h was observed at a dilution rate of 0.51 h−1. At this dilution rate, only 68% of the COD was removed. A 95% COD removal was attained at a dilution rate of 0.10 h−1. Optimal yeast productivity and COD reduction occurred at a dilution rate of 0.33 h−1.
Pilot‐and production‐scale containment of cytotoxic and oncogenic fermentation processes
Authors: Flickinger M. C. , Sansone E. B. 
Published: December 2004

AbstractProper design of fermentation facilities and equipment modification can control the risks associated with largescale production and purification of microbially produced cytotoxic agents and oncogenic viruses. The primary biohazard risks to operators and the environment are generation of aerosols and accidental spills. Fermentation and recovery facilities can be constructed to contain these agents by installing fermentation equipment within a HEPA‐filter‐exhausted biological barrier. Within this barrier system, large‐scale processing that generates potentially hazaradous areosols (filtration, centrifugation of transformed cells or crystal slurries, and banding of viruses) should be isolated from other operations. Isolation of equipment is often required, with provision for both chemical and biological decontamination of process wastes. Failsafe fermentor over‐pressure sensors, parallel exhaust gas filtration, welded transfer lines, and modified sampling systems for elimination of aerosols can be installed on most fermentation equipment. Aerosol and spill containment by proper equipment design, coupled with appropriate personnel protective equipment and medical monitoring, make possible safe production of experimental growth factors and viruses from large‐scale culture of transformed mammalian cells and production of cytotoxic antitumor antibiotics.
A comparison of two empirical models for the enzymatic hydrolysis of pretreated poplar wood
Authors: Holtzapple Mark T. , Caram Hugo S. , Humphrey Arthur E. 
Published: December 2004

AbstractTwo empirical models for the enzymatic hydrolysis of cellulose are used to analyze the same set of experimental data to determine if one model is superior to the other. Both models adequately describe the data. The parameters in both models may be correlated to the hydrolysis conditions of enzyme, substrate, and product inhibitor concentrations. Both empirical models have features which are consistent with theoretical models of cellulose hydrolysis.