bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of a metabolically structured model in the study of growth, nitrification, and denitrification by Thiosphaera pantotropha
Authors: Geraats S. G. M. , Hooijmans C. M. , van Niel E. W. J. , Robertson L. A. , Heijnen J. J. , Luyben K. Ch. A. M. , Kuenen J. G. 
Published: December 2004

AbstractThiosphaera pantotropha is capable of aerobic heterotrophic nitrification and both aerobic and anaerobic denitrification. These phenomena have been studied in acetate‐limited aerobic and anaerobic continuous cultures supplied with ammonia and nitrate. The internal reaction rates were defined, based on biochemical knowledge. The observable external conversion rates are related through a linear equation on the basis of the specified internal reaction rates. The linear equation is a Pirt relation extended for microbial systems with multiple electron donors (acetate and ammonia) and electron acceptors (oxygen and nitrate). The coefficients in this equation were estimated from the continuous culture measurements, and are composed of parameters involved in ATP production and consumption by the microorganism. It is shown that with realistic values for these parameters, the metabolically structured model describes the aerobic as well as the anaerobic experiments.
Physiological, biochemical, and mathematical studies of micro‐aerobic continuous ethanol fermentation by Saccharomyces cerevisiae. II: Intracellular metabolite and enzyme assays at steady state chemostat cultures
Authors: Grosz Ron , Stephanopoulos Gregory 
Published: December 2004

AbstractIntracellular metabolite concentration and enzyme activity measurements were made to explain the new metabolic and growth phenomena seen in the micro‐aerobic, continuous yeast cultures described in Part I. The results of these assays suggested mechanisms for the observed maximum in the specific ethanol productivity as a function of the oxygen feed rate, changing ATP yields, the effects of antifoam, and the sharp changes in the biomass concentration with small changes in the oxygenation. Measured were the intracellular concentrations of ATP, NADH, glucose 6‐phosphate, pyruvate, glycerol, and ethanol, and the activities of hexokinase and alcohol dehydrogenase. Rate‐limiting steps were identified by the accumulation of metabolites upstream and the depletion of metabolites downstream of the step.A potential mechanism for the stimulation of fermentation with decreasing oxygenation was an activation of glucose transport by an accumulating intracellular ATP concentration. The inhibition of fermentation at yet lower oxygenation rates may have been caused by the continued accumulation of ATP to the point that the glycolytic kineses were inhibited. A mechanism for the changing ATP yields and intracellular ATP concentration proposed the existence of ATPases or ATP waste reactions stimulated by both oxygen and ATP. Antifoam had the effect of decreasing the resistance for glycerol transport out of the cell. The resulting stimulation of glycerol production and inhibition of ethanol production decreased the intracellular ATP content. Finally, intracellular ethanol was found not to accumulate to levels of higher than the extracellular concentration.
Immobilization can improve the stability of hybridoma antibody productivity in serum‐free media
Authors: Lee Gyun Min , Palsson Bernhard O. 
Published: December 2004

AbstractHybridoma cells (S3H5/γ2bA2) were cultivated in spinner flasks with 1% serum media and serum‐free media. Monoclonal antibody productivity was maintained in 1% serum media. However, cells in serum‐free media showed a decrease in antibody productivity, and it completely disappeared in IMDM‐based low protein medium. This loss of antibody productivity was not observed when the cells were immobilized in alginate beads. In fact, immobilization enhanced the specific MAb productivity.
A completely automated system for on‐line monitoring of the production of a growth factor secreted during fermentation of Escherichia coli
Authors: Lundström Håkan , Brobjer Michael , Österlöf Björn , Moks Tomas 
Published: December 2004

AbstractThe production of IGF‐1 (insulin‐like growth factor 1), expressed in Escherichia coli as a secreted fusion protein with affinity for the Fc region of IgG, was monitored automatically during fermentations. A sampling device was used to automatically inject filtered culture medium from the fermentor onto a small affinity column (IgG Sepharose® Fast Flow) connected to a chromatographic system. The area of the eluted peak was proportional to the concentration of the fusion protein. The relationship was linear over the range 25–630 μg/mL with relative standard deviation of around 1% at the higher concentrations. Samples could be monitored automatically every half hour during fermentation (48 h). The method of analysis is nondestructive, allowing further analysis of product quality. A complete evaluation of the monitoring system is described. With this system, fermentations based on the described expression system can be optimized on the basis of product concentration; this will lead to more effective fermentations and higher product yields. It should also be possible to monitor other secreted products with this system by using other affinity gels.
Investigation of binding site density: Effects on the interaction between cibacron blue–dextran conjugates and lysozyme
Authors: Mayes A. G. , Moore J. D. , Eisenthal R. , Hubble J. 
Published: December 2004

AbstractCibacron‐blue–dextran conjugates have been produced with a range of ligand loadings using a dextran preparation of average molecular weight of 2 × 106. The equilibrium binding capacity of these ligand conjugates for lysozyme was determined using a gel permeation procedure to separate bound from free protein. The results obtained give clear evidence for at least two types of binding showing a marked difference in affinity. For the higher‐affinity interaction the half‐saturation constant decreases with increasing ligand loading. The number of dye molecules participating in binding is proportional to loading up to 154 mol dye/mol dextran but is reduced at the highest loading used (315 mol dye/mol dextran). This may be due to steric interference or to dye stacking reducing the number of dye molecules available for binding.
An approach for the stable immobilization of proteins
Authors: Leckband Deborah , Langer Robert 
Published: December 2004

AbstractAn approach is presented for the stable covalent immobilization of proteins with a high retention of biological activity. First, chemical modification studies were used to establish enzyme structural and functional properties relevant to the covalent immobilization of an enzyme to agarose based supports. Heparinase was used as a model enzyme in this set of studies. Amine modifications result in 75–100% activity loss, but the effect is moderated by a reduction in the degree of derivatization. N‐hydroxysuccinimide, 1,1,1‐trifluoroethanesulfonic acid, and epoxide activated agarose were utilized to determine the effect of amine reactive supports on immobilized enzyme activity retention. Cysteine modifications resulted in 25–50% loss in activity, but free cysteines were inaccessible to either immobilized bromoacetyl or p‐chloromercuribenzoyl groups. Amine reactive coupling chemistries were therefore utilized for the covalent immobilization of heparinase. Second, to ensure maximal stability of the immobile protein–support linkage, the identification and subsequent elimination of the principal sources of protein detachment were systematically investigated. By using high‐performance liquid chromatography (HPLC), electrophoresis, and radiolabeling techniques, the relative contributions of four potential detachment mechanisms—support degradation, proteolytic degradation, desorption of noncovalently bound protein, and bond solvolysis—were quantified. The mechanisms of lysozyme, bovine serum albumin, and heparinase leakage from N‐hydroxysuccinimide or 1,1,1‐trifluoroethanesulfonic acid activated agarose were elucidated. By use of stringent postimmobilization support wash procedures, noncovalently bound protein loss. An effective postimmobilization washing procedure is presented for the removal of adsorbed protein and the complete elimination of immobilized protein loss.
Continuous anaerobic treatment of autoxidized bark extracts in laboratory‐scale columns
Authors: Field J. , Leyendeckers M. J. H. , Sierra‐Alvarez R. , Lettinga G. , Habets L. H. A. 
Published: December 2004

AbstractDebarking wastewaters of the forest industry contain high concentrations of tannins that are inhibitory to methane bacteria. The tannins can be polymerized to nontoxic colored compounds by the applications of an autoxidation pretreatment, enabling the anaerobic treatment of easily biodegradable components in the wastewater. The continuous anaerobic treatment of untreated and autoxidized pine bark extract was studied in laboratory‐scale columns packed with a granular sludge bed. The autoxidation doubled the conversion efficiency of bark extract COD to methane (from 19 to 40%). After 5 months of operation, anaerobic treatment of the autoxidized extracts was feasible at high influent concentrations (14 g COD/L) and loading rates (26 g biodegradable COD/L · d) with 98% elimination of the biodegradable fraction. The detoxification pretreatment polymerized the toxic tannins to poorly biodegradable high molecular weight tannins and humic compounds which were not eliminated during anaerobic treatment. Although the original tannins of the untreated extract were eliminated by 60%, they were not biodegraded to volatile fatty acids and methane but instead were transformed to phenolic degradation intermediates (phenol, p‐cresol, 3‐phenyl‐propionate, and carboxycyclohexane). Therefore, the autoxidation pretreatment did not decrease the content of readily biodegradable substrates which accounted for 53% of the extract COD. The recalcitrant COD expected in the effluents of reactors treating autoxidized debarking waste‐water can be effectively separated by calcium precipitation prior to anaerobic treatment.
The interaction of xylanases with commercial pulps
Authors: Senior D. J. , Mayers P. R. , Saddler J. N. 
Published: December 2004

AbstractWhen purified xylanases from Trichoderma harzianum E58 or from a clone of Bacillus circulans were incubated with various low‐yield wood pulps, little of the original enzyme activity could be detected in the filtrate at the end of the reaction. Partial bleaching of the pulps prior to enzymatic treatment generally resulted in an increased recovery of the xylanase activity. It appears that both nonspecific adsorption and soluble inhibitors may be responsible for the loss of much of the xylanase activity. However, xylanases from Aureobasidium pullulans and Schizophyllum commune were not as inhibited by the pulps, and the activity of the latter enzyme actually increased after incubation with several high‐yield pulps. Although a lignin preparation from spent sulfite liquor at a concentration of 0.06 mg/mL could inhibit the xylanase activity of T. harzianum and B. circulans by 65% and 50%, respectively, xylanases from Thermoascus aurantiacus, S. commune, and A. pullulans were activated at similar lignin concentrations. At higher concentrations these latter xylanases were also inhibited. Water‐soluble lignins extracted from a variety of pulps and used at a lignin concentration of 2.5 μg/mL resulted in inhibition of more than 65% of the original activity of the xylanase from T. harzianum. Kinetic studies showed that lignin from spent sulfite liquor resulted in noncompetitive inhibition of this enzyme.
Plant cell bioreactor for the production of protoberberine alkaloids from immobilized Thalictrum rugosum cultures
Authors: Facchini Peter J. , Dicosmo Frank 
Published: December 2004

AbstractCultured Thalictrum rugosum cells were immobilized using a glass fiber substratum previously shown to provide optimum immobilization efficiency based on spontaneous adhesion mechanisms. When cultivated in shake flasks, immobilized cells exhibited decreased growth and protoberberine alkaloid production rates in comparison to freely suspended cells. Since alkaloid production is growth associated in T. rugosum, the decreased specific production rate was a function of the slower growth rate. Cells immobilized on glass fiber mats appear to be amenable for extended culture periods. Maximum biomass and protoberberine alkaloid levels were maintained for at least 14 days in immobilized cultures. In contrast, fresh weight, dry weight, and total alkaloid content decreased in suspension cultures following the linear growth phase.Glass fiber mats were incorporated in to a 4.5‐L plant cell bioreactor as horizontal disks supported on a central rod. Mixing in the reactor was provided by the combined actions of a magnetic impeller and a cylindrical sparging colum. fThe magnetic impeller and a cylindrical sparging column. The entire inoculum biomass of T. rougosum, introduced as suspension, was spontaneously immobilized with in 8h. During liner phase, the growth rate of bioreactor cultivated immobilized cells (μ = 0.06 day−1) was 50% that immobilized cell viability in both systems was determined to be similar. The increase in specific production of protoberberine alklodis was initially similar in bioreactor‐and culture period. The increase in specific production of protoberberine alkaloids was initially similar in bioreactor‐and shake‐flask‐cultivated immobilized cells. However, the maximum specific production of bioreactor grown cultures was lower. The scale up potential of an immobilization strategy based on the spontaneous adhesion of immobilization strategy based on the spontaneous adhesion of cultured plant cells to glass fiber is demonstrated.
Morphology and clavulanic acid production of Streptomyces clavuligerus: Effect of stirrer speed in batch fermentations
Authors: Belmar‐Beiny M. T. , Thomas C. R. 
Published: December 2004

AbstractStreptomyces clavuligerus ATCC 20764 was grown from spore‐inocuia on a glycerol, malt extract, bacteriological peptone medium in 5‐L batch fermentations at 490, 990, and 1300 rpm. Dry cell weights, clavulanic acid production, and the morphological parameters main hyphal length, total hyphal length, number of tips, and hyphal growth unit were measured. Growth and productivity were hardly dependent on stirrer speed. After early growth fragmentation of long, highly branched mycelia to shorter, less branched fragments occurred. This was followed by regrowth and, at 1300 rpm, a second fragmentation phase. The effect of increasing stirrer speed was to accelerate the initial fragmentation phase. It was clearly possible to obtain the same biomass concentration and clavulanic acid liter, with different morphologies depending on stirrer speed. This shows that for this fermentation at least there is no direct link between morphology and productivity and, hence, that it might be possible to manipulate them independently to improve fermentor performance.
Oxidation of hydrogen sulfide by flocculated Thiobaccillus denitrificans in a continuous culture
Authors: Ongcharit Chawan , Sublette Kerry L. , Shah Y. T. 
Published: December 2004

AbstractIn a continuous fermentation, significant advantages may be gained by immobilization of microbial cells. Immobilization allows cells to be retained in the fermenter or to be readily recovered and recycled. Therefore, the hydraulic retention time and the biomass retention time are decoupled. A novel cell immobilization has been developed for the immobilization of autotrophic bacteria by coculture with floc‐forming heterotrophic bacteria with growth of the latter limited by the availability of organic carbon. The result is an immobilization matrix which grows along with the immobilized autotroph. We have previously demonstrated the utility of this approach by immobilizing the chemoautotroph Thiobacillus denitrificans in macroscopic floc by coculture with floc‐forming heterotrophs from an activated sludge treatment facility. Floc with excellent settling characteristics were produced. These floc have now been used to remove H2S from a gas stream bubbled through continuous cultures. The stoichiometry and kinetics of H2S oxidation by immobilized T. denitrificans were comparable to that reported previously for free‐cell cultures. Oxygen uptake measurements indicated the growth of both T. denitrificans and the heterotrophs although the medium contained no added organic carbon. Continuous cultures with total biomass recycle were maintained for up to four months indicating the long‐term stability of the commensal relationship between the immobilized autotroph and the heterotrophs which composed the immobilization matrix. It was observed that at any given H2S loading the biomass concentration reached a maximum and leveled out. The ultimate biomass concentration was dependent upon the H2S feed rate.
Adsorption of γ‐globulin, a model protein for antibody, on colloidal particles
Authors: Kondo Akihiko , Oku Shinya , Higashitani Ko 
Published: December 2004

AbstractThe effect of surface properties on the adsorption of bovine γ‐globulin, a model protein for antibody, was studied. Polystyrene latex (PS), hydrophilic copolymer lattices of styrene/2‐hydroxyethyl methacrylate [P(S/HEMA)], styrene/ methacrylic acid [P(S/MAA)] and methyl methacrylate/ 2‐hydroxyethyl methacrylate [P(MMA/HEMA)], and colloidal silica were used. The adsorption isotherms of γ‐globulin on these colloidal particles were measured as a function of pH and ionic strength. The hydrophilic particles showed low affinities for γ‐globulin at alkaline pH, while PS showed high affinities for γ‐globulin over the whole range of pH and ionic strength. The γ‐globulin adsorption on hydrophilic particles was highly reversible with respect to the pH and ionic strength compared with that on PS. These differences indicate that the dominant driving forces of adsorption are related to the hydrophilicity of particles. The adsorption isotherms of all colloidal particles showed the plateau values, and the order of maximum values of plateau adsorption was P(S/MAA) > PS or P(S/HEMA), silica > P(MMA/HEMA). Thus, they were also affected by the charged groups and the hydrophilicity of the surfaces. On the other hand, the plateau values of all colloidal particles were more or less symmetrical with a maximum at around the isoelectric point of γ‐globulin at an ionic strength of 0.01. This behavior is attributed to the important role of the lateral interaction between the adsorbed molecules at low ionic strength.
Effect of operating variables on biofilm formation and performance of an anaerobic fluidized‐bed bioreactor
Authors: Sreekrishnan T. R. , Ramachandran K. B. , Ghosh P. 
Published: December 2004

AbstractThe effect of various operating variables such as initial inoculum circulation, dilution rate, chemical oxygen demand (COD) loading rate, and quantity and quality of inoculum on the process of film formation on sand surface and reactor performance were studied using synthetic glucose based wastewater. It was found that the film formation process is favored by a high dilution rate, a large quantity of inoculum, and an inoculum having high methane producing capacity. Experimental observations indicate that the biofilm formation process is initiated by methanogenic bacteria.
The effect of dissolved oxygen and aeration rate on antibiotic production of Streptomyces fradiae
Authors: Chen H. C. , Wilde F. 
Published: December 2004

AbstractDifferent dissolved oxygen concentrations and aeration rates were imposed on a stable mutant of Streptomyces fradiae during the antibiotic‐producing phase. At high aeration rate (1 vvm), the tylosin yield in the fermentor broth with dissolved oxygen (DO) concentrations controlled close to 100% saturation (6–8 ppm) increased 10% as against uncontrolled. The rates of cellular growth, oil consumption, and tylosin production were severely reduced when DO concentration fell below 25% saturation, but all resumed to their initial rates when DO was raised to saturation level again. The DO concentration in combination with air flow rate affected the pattern of the antibiotics produced. At high DO levels, an additional macrolide antibiotic, macrocin, was synthesized to more than one‐third the amount of tylosin at high aeration rate (1 vvm). On the other hand, tylosin production rate remained constant and no significant amount of macrocin was produced at low aeration rate (0.2 vvm).
Flotation of Streptomyces pilosus after lead accumulation
Authors: Sadowski Z. , Golab Z. , Smith R. W. 
Published: December 2004

AbstractThe flotation of Streptomyces pilosus was studied in the absence and presence of adsorbed Pb(II) ions on the cell walls and with and without using sodium dodecylsulfate (SDS) as collector. Adsorption of SDS onto the organism in the absence and presence of Pb(II) ions was also investigated. It was found that in the absence of adsorbed Pb(II), very little flotation took place with or without the presence of SDS although SDS adsorbed to some extent on the organism. The presence of Pb(II) on the bacterium's cell walls significantly increased flotation even in the absence of the collector. Addition of SDS, however, further increased both flotation rate and recovery.
A semimechanistic mathematical model for growth of Rhizopus oligosporus in a model solid‐state fermentation system
Authors: Mitchell David A. , Do Duong D. , Greenfield Paul F. , Doelle Horst W. 
Published: December 2004

AbstractA Semimechanistic mathematical model is developed which describes the growth of Rhizopus oligosporus in a model solid‐state fermentation system. Equations are presented for the release of glucoamylase, the diffusion of glucoamylase, the hydrolysis of starch, the generation and diffusion of glucose, and the uptake of glucose and conversion into new biomass. Good agreement of the model with the experimental data was obtained only after the glucoamylase diffusivity and the maximum specific glucose uptake rate were altered from their originally determined values. The model recognizes the distributed nature of the solid‐state fermentation and therefore is able to predict the concentration profiles of the system components within the substrate. The model provides an insight into the possible rate‐limiting steps in solid‐state fermentation—the generation of glucose within the substrate and the resulting availability of glucose at the surface.
1‐Monoglyceride production from lipase‐catalyzed esterification of glycerol and fatty acid in reverse micelles
Authors: Hayes Douglas G. , Gulari Erdogan 
Published: December 2004

AbstractGlycerol‐fatty acid esterification has been conducted with lipase from R. delemar in water/AOT/isooctane reverse micellar media, with the major product being 1‐monoglyceride, a useful food‐emulsifier. 1,3‐diglyceride was also synthesized, but to a much lesser extent. For a given set of initial conditions, the reaction productivity, measured in terms of the initial product formation rate, V0, and the final or equilibrium concentration of product, is optimal for a particular concentration of each surfactant, fatty acid, glycerol, and water. Many of these optimal values correlate well with a “critical” region on the phase diagram. Also, results indicate lipase‐catalyzed esterification stops due to the achievement of kinetic equilibrium expect for a few cases where enzyme deactivation is severe. Dynamic light scattering was employed to examine the influence of water, glycerol, and fatty acid on micellar and interfacial structure. Results from this technique indicate enzyme kinetic are linked to interfacial phenomena and the presence of substrates at the interfacial region.