bluuebunny/crossref_metadata_2025_split huggingface dataset:
A segregated model of recombinant multicopy plasmid propagation
Authors: Wittrup K. D. , Bailey J. E. 
Published: December 2004

AbstractA segregated model of multicopy plasmid propagation has been formulated which incorporates plasmid replication and partition functions, as well as the effect of plasmid presence on host growth rate. Growth of plasmid‐free cells in selective medium is explicitly analyzed. The model parameters can be determined from experimentally measurable quantities. Propagation of a recombinant multicopy plasmid in the yeast Saccharomyces cerevisiae is analyzed using this model.
Elucidation of enzyme control mechanisms using macroscopic measurements in a mixed substrate fermentation system
Authors: Pih Norman , De Bernardez Eliana , Dhurjati Prasad 
Published: December 2004

AbstractThe objective of this work was to relate macroscopically measurable on‐line fermentation parameters such as dissolved oxygen, off‐gas oxygen and carbon dioxide, and cell mass, to the controlled production of key intracellular enzymes under carbon limited conditions. Both batch and perturbed batch aerobic fermentations were performed using two different strains of Escherichia coli, with glucose and lactose as the sole carbon sources. The two strains differed from each other only in the lac operon region of their genome. The parent strain, E. coli 3000, was inducible for the enzyme β‐galactosidase. The other strain, E. coli 3300, was a constitutive mutant in the production of β‐galactosidase. In all experiments, off‐line assays of sugars and β‐galactosidase activity were performed. It was observed that there is a clear relationship between the macroscopic on‐line measurements, dissolved oxygen tension, carbon dioxide evolution rate and oxygen uptake rate, and the microscopic control phenomena of catabolite repression, catabolite inhibition, and inducer repression.
Hydrolysis of beet pulp polysaccharides by extracts of solid‐state cultures of Pencicillium capsulatum
Authors: Considine P. J. , O'Rorke A. , Hackett T. J. , Coughlan M. P. 
Published: December 2004

AbstractExtracts of solid‐state cultures of Penicillium capsulatum grown on beet pulp exhibit cellulolytic, hemicellulolytic, and pectinolytic activities. Such extracts catalyzed extensive solubilization of untreated beet pulp. The effects of pH, temperature, and endproducts on the saccharification process were investigated.
Synthesis and characterization of a water‐soluble affinity polymer for trypsin purification
Authors: Luong J. H. T. , Male K. B. , Nguyen A. L. 
Published: December 2004

AbstractA specific ligand bound polymer has been synthesized for the purpose of purification and stabilization of trypsin, an easily autodigestible enzyme. The affinity polymer was formed by copolymerizing N‐acryloyl‐m‐aminobenzamidine, a strong trypsin inhibitor, and acrylamide in the absence of oxygen. Kinetic studies on the trypsin inhibition revealed that there was a strong binding between this enzyme and the polymer and the mechanism was of a competitive manner with an inhibition constant of 0.6 × 10−3M. Such an affinity polymer was also very effective in preventing trypsin from auto‐digestion at 4°C.Based on this finding and the principle of cross flow filtration, a new process has been developed for purification of trypsin from a solution containing chymotrypsin. The experimental data indicated that trypsin was bound to the polymer (MW > 105) and remained in the retentate while unbound chymotrypsin was collected in the filtrate. This purification process has a capability of recovering 98% pure trypsin at 90% yield.
MPS: An artificially intelligent software system for the analysis and synthesis of metabolic pathways
Authors: Seressiotis Alex , Bailey James E. 
Published: December 2004

AbstractThe concepts of artificial intelligence have been applied for the development of a software system for metabolic pathway synthesis (MPS). An easily expandable data base system for storing enzyme and substance descriptions is used by a search algorithm for the identification of possible ways to interconvert carbon‐carrying metabolites. A versatile screening capability permits the user to identify all pathways which contain or exclude any combination of enzymes, substrates, and/or products. Information provided by MPS can be used to predict on a qualitative basis the effects of adding or deleting enzymatic activities to or from the cellular environment, to classify pathways with respect to cellular objectives, and to extract information about metabolic regulation. MPS can be used subsequently to aid the identification of appropriate genotypes or genetic modifications that will redirect metabolism towards amplified production of desirable bioproducts. Two examples illustrating the capabilities of MPS are presented. In the first example, which considers the conversion of glucose 6‐phosphate to pyruvate, MPS synthesized the classical catabolic pathways (EMP, pentose phosphate and ED) along with possible variations. A route for the biosynthesis of L‐alanine that does not incorporate the enzyme alanine aminotransferase was revealed by MPS during synthesis of alternative pathways which produce L‐alanine from pyruvate.
Organosolv pretreatment for enzymatic hydrolysis of poplars: I. Enzyme hydrolysis of cellulosic residues
Authors: Chum H. L. , Johnson D. K. , Black S. , Baker J. , Grohmann K. , Sarkanen K. V. , Wallace K. , Schroeder H. A. 
Published: December 2004

AbstractAspen (Populus tremuloides) and black cottonwood (Populus trichocarpa) organosolv pulps produced in a wide range of solvent composition (between 30 and 70% by volume of methanol) and catalysts (H2SO4 and H3PO4) such that the cooking liquor pH ⩽ 3 are easily digested by enzymes. The total yields of hydrolysis residues (pulps) are in the 40–60% range; the acid‐catalyzed delignification followed by enzyme hydrolysis can generate 70–88% of the original six‐carbon sugars contained in the wood. Glucomannan and arablnogalactan are dissolved into the pulping liquor in the pH range of 2–4.5. Lower pH (⩽3) leads to additional solubilization of six‐carbon sugars. These sugars may be fermented directly. From the insoluble hydrolysis residues, 36–41% conversions of wood into fermentable sugars were obtained after enzyme hydrolysis; the starting feedstocks contain 50.8 and 46.6% hexosans, respectively, for aspen and black cotton‐wood. The kinetics of enzymatic hydrolysis of cellulose can be formally treated as two simultaneous pseudo‐first‐order reactions in which fast and slow hydrolyses of cellulose occur. Correlations between the glucan digestibility and the effect of the pretreatment have been made. The higher residual xylan content reduces the amount of the rapidly hydrolyzable glucan fraction and lowers the glucan digestibility. The proposed simple kinetic treatment is very helpful in assessing the effect of the pretreatment on pulp enzyme hydrolyzability.
pH and trace‐elements content in raisin extract industrial‐scale alcoholic fermentation
Authors: Akrida‐Demertzi K. , Demertzis P. G. , Koutinas A. A. 
Published: December 2004

AbstractThe ability of all kinds of Greek raisins for the industrial‐scale fermentation related to pH and trace‐element contents is discussed. In the case of raisin extracts of pH 3.2 larger ethanol productivities, yields, and a continuous use of the same yeast culture at a level of 300 batches was obtained. Metals such as Co, Fe, Zn, Cu, Cd, and Pb in all kinds of raisins have been determined using atomic absorption spectroscopy. The raisin variety Trechumena contains the smallest amount of Cu, and the variety Psilla contains 7 times higher concentration than Trechumena. This is in agreement with the fact that Psilla is the worst kind of raisin and Trechumena the best for spirit production. This observation is related with experimental results obtained by alcoholic fermentation in a series of synthetic media containing sacharose and different concentrations of copper.
Two‐Liquid phase reactor studies of 11α‐hydroxylation of progesterone by Aspergillus ochraceus
Authors: Ceen E. G. , Dunnili P. , Herrmann J. P. R. 
Published: December 2004

AbstractThe 11α‐hydroxylation of progesterone by free cells of Aspergillus ochraceus has been examined in a reactor with an aqueous and a natural oil phase. As the proportion of oil is increased, the point of inversion from a continuous aqueous phase is affected by the cell concentration, as is the optimum ratio of the phases for conversion. High oil ratios are not productive because of poor mass transfer to the concentrated cells in the aqueous phase. The cells are stable in the presence of oleic acid for at least 24 h.
The effective diffusive permeability of a nonreacting solute in microbial cell aggregates
Authors: Libicki Shari B. , Salmon Peter M. , Robertson Channing R. 
Published: December 2004

AbstractAggregates of Escherichia coli confined within hollowfiber reactors were either formed in place by culturing cells within the reactors, or were prepared by injecting a cell suspension that had been concentrated by centrifugation. The effective diffusive permeability of an uncharged nonreacting tracer, nitrous oxide, within the cell aggregates was calculated from measurements of the tracer flux through the aggregates. Estimates of the hydraulic permeability were also obtained for the aggregates that were grown in place. The effective diffusive permeability was found to decrease with increasing cell volume fraction to a value, for aggregates comprising 95% cells, of ca. 30% that obtained for cell‐free buffer solution. The dependence on the cell volume fraction was described adequately by the well‐known HashinShtrikman bounds for a two‐phase medium. The transport properties of aggregates cultivated in place were not significantly different from those of aggregates prepared by centrifugation. Furthermore, the effective diffusive permeabilities of the tracer in aggregates prepared from cells treated with detergent or disrupted by dehydration and grinding differed only slightly from the values obtained for aggregates formed from untreated cells. The results suggest that the method of formation of the cell aggregate and the details of the structure of the cells have little influence on the effective diffusive permeability. These findings should be applicable to the transport of other small uncharged solutes, such as oxygen, that can diffuse through cells. The hydraulic permeability estimates for the aggregates cultured in place were several orders of magnitude larger than the values predicted by a theory formulated with the assumption that the cells are impervious to flow and homogeneously distributed within the aggregates. Two possible reasons for this discrepancy are, first, that there is some flow through the cells themselves, and second, that the cells may form discrete clusters separated by relatively open regions.
Bacterial leaching of a sulfide ore by Thiobacillus ferrooxidans and Thiobacillus thiooxidans: I. Shake flask studies
Authors: Lizama Hector M. , Suzuki Isamu 
Published: December 2004

AbstractBacterial leaching of a sulfide ore containing pyrite, chalcopyrite, and sphalerite was studied in shake flask experiments using Thiobacillus ferrooxidans and Thiobacillus thiooxidans strains isolated from mine sites. The Fe2+grown T. ferrooxidans isolates solubilized sphalerite preferentially over chalcopyrite leaching 7–10% Cu, 68–76% Zn, and 10–22% Fe from the ore in 18 days. The sulfur grown T. thiooxidans isolates leached Zn much more slowly and very little Fe, with a Cu–Zn extraction ratio twice the value obtained with T. ferrooxidans. The ore adapted T. ferrooxidans started solubilizing Cu and Zn without a lag period. The ore‐adapted T. thiooxidans extracted Cu as well as T. ferrooxidans, but the extraction of Zn or Fe was still much slower in the low‐phosphate medium, while in the high‐phosphate medium it approached the value obtained with T. ferrooxidans. A high Cu–Zn extraction ratio of 0.34 was obtained with T. thiooxidans in the low phosphate medium. In the mixed‐culture experiments with T. ferrooxidans and T. thiooxidans, the culture behaved as T. thiooxidans in the low‐phosphate medium with a higher Cu–Zn extraction ratio and as T. ferrooxidans in the high‐phosphate medium with a lower Cu–Zn extraction ratio. It is concluded that T. ferrooxidans and T. thiooxidans solubilize sulfide minerals by different mechanisms.
Immobilization of glucose oxidase on polymer membranes treated by low‐temperature plasma
Authors: Kawakami Mitsuyasu , Koya Hidekazu , Gondo Shinichiro 
Published: December 2004

AbstractLow‐temperature plasma was employed for activation of polymer membranes as a carrier for enzyme immobilization. Glucose oxidase was immobilized on polypropylene (PP), polyvinylidene fluoride (PVDF), or polytetrafluoroethylene (PTFE) membrane surfaces treated by nitrogen or ammonia gas plasma using glutaraldehyde as a linking agent. Enzyme activity was evaluated by the response of glucose sensor composed of the immobilized enzyme membrane and a dissolved oxygen electrode. The sensor response was found to depend on the kind of carrier membrane and to become maximum at suitable conditions of plasma treatment.
Effect of ethanol on glucose transport, key glycolytic enzymes, and proton extrusion in Saccharomyces cerevisiae
Authors: Pascual Carlos , Alonso Alberto , Garcia Isabel , Romay Cheyla , Kotyk Arnošt 
Published: December 2004

AbstractThe effect of ethanol on the activities of the key enzymes of the glycolytic pathway and on two membrane functions related with fermentation, the glucose uptake system, and proton extrusion rate are examined. The results indicate that ethanol, up to 2M, does not cause any change of the glucose uptake velocity nor any substantial change in the key glycolytic enzyme activities while the fermentation rate is reduced by about 50%. In a cell extract 3M ethanol as well as incubation of yeast cells with 4M ethanol caused a considerable decrease of pyruvate kinase and hexokinase activities. Phosphofructokinase remained unchanged even at higher ethanol concentrations. Transmembrane proton flow was found to be the most sensitive of the functions tested toward ethanol, and it could represent the first target of ethanol action on fermentation.
Effect of hydrogen and carbon dioxide partial pressures on growth and sulfide production of the extremely thermophilic archaebacterium Pyrodictium brockii
Authors: Parameswaran A. K. , Schicho R. N. , Soisson J. P. , Kelly R. M. 
Published: December 2004

AbstractThe effect of hydrogen and carbon dioxide partial pressure on the growth of the extremely thermophilic archaebacterium Pyrodictium brockii at 98°C was investigated. Previous work with this bacterium has been done using an 80:20 hydrogen‐carbon dioxide gas phase with a total pressure of 4 atm; no attempt has been made to determine if this mixture is optimal. It was found in this study that reduced hydrogen partial pressures affected cell yield, growth rate, and sulfide production. The effect of hydrogen partial pressure on cell yield and growth rate was less dramatic when compared to the effect on sulfide production, which was not found to be growth‐associated. Carbon dioxide was also found to affect growth but only at very low partial pressures. The relationship between growth rate and substrate concentration could be correlated with a Monod‐type expression for either carbon dioxide or hydrogen as the limiting substrate. The results from this study indicate that a balance must be struck between cell yields and sulfide production in choosing an optimal hydrogen partial pressure for the growth of P. brockii.
Continuous production of maltotetraose using immobilized Pseudomonas stutzeri amylase
Authors: Kimura Takashi , Ogata Masafumi , Yoshida Masahiro , Nakakuki Teruo 
Published: December 2004

AbstractA continuous production process of maltotetraose was investigated by using immobilized maltotetraose (G4)‐ forming amylase (1,4‐α‐D‐glucan maltotetraohydrolase, EC3.2.1.60) from Pseudomonas stutzeri adsorbed on a macroporous hydrophobic resin. The maximum reaction rate was obtained at 55°C and the activation energy of hydrolysis by immobilized G4‐forming amylase was calculated to be 8.45 kcal/mol. The maltotetraose yield was greatly influenced by the flow rate of substrate solution, its concentration, and the immobilized enzyme activity. The newly defined factor “specific space velocity” was successfully introduced to normalize the operating parameters. Using this factor, the immobilized enzyme reactor then can be simulated and the operating dynamics can be determined.
Immobilization of proteins on organic polymer beads
Authors: Ampon Kamaruzaman , Means Gary E. 
Published: December 2004

AbstractA new method is described for the immobilization of biologically active proteins onto several types of organic polymer beads. First, the soluble protein is modified by reaction with an excess of a hydrophobic imidoester, for example methyl 4‐phenyl‐butyrimidate, at ca. pH 9 and 0°. Excess imidoester and side products resulting from imidoester hydrolysis are separated from the hydrophobic protein derivative by exclusion chromatography or dialysis. A suspension of polymer beads (e.g. Amberlite XAD‐7) is then added to a solution of the modified protein at room temperature or below and stirred gently for 1‐2 h. The polymer beads are allowed to settle, separated from the solution by decantation or filtration, washed, and resuspended in an appropriate buffer. Quantitative adsorption of protein to the polymer beads is observed under such conditions. The synthesis of seven hydrophobic imidoesters and their use for the immobilization of trypsin onto several types of porous polymer beads is described. The immobilizations of trypsin, yeast alcohol dehydrogenase, and E. coli asparaginase by this procedure with high recoveries of catalytic activity, suggests that it will be applicable to a large number of biologically active proteins.
Microalgae production: Technical and economic evaluations
Authors: Tapie P. , Bernard A. 
Published: December 2004

AbstractA review of the various literature data for large‐scale algae production costs is described. Costs were updated and recomputed in order to compare the different schemes. Total production costs of a nonprocessed biomass range from US$0.15 to US$4.0 kg−1, according to various authors. Process performance hypotheses and proposed technologies are analyzed to explain these variations. A cost analysis for a tubular bioreactor system is then presented that shows that, assuming a productivity of 60 tons/ha yr, production costs would range from FF24 to FF29 kg−1 for such a system. Operating costs as well as fixed charges account for approximately 50% of the cost. Parametric sensitivity of these costs is then analyzed: If productivity would be 30, 45, or 90 tons/ha yr, total cost would be around FF48, FF33 and FF19 kg−1. Advantages and disadvantages of the proposed tubular technology are finally discussed.
Optimization of enzymatic lysis of yeast
Authors: Liu Lee‐Cheng , Prokopakis George J. , Asenjo Juan A. 
Published: December 2004

AbstractIn enzymatic lysis of yeast for the recovery of intracellular proteins, the rupture of whole cells is caused by the action of a lytic system consisting primarily of protease and glucanase. A first‐principles mechanism for the lytic reaction based on a two‐layer model of the wall structure and a burst model for the disruption of cells is pre sented. The fed‐batch model results in a dynamic optimization problem, with the enzymes, activities being the control variables. Orthogonal collocation is applied to discretize the state equations, and the resulting non linear program is solved using successive quadratic pro gramming to determine the enzyme and protease inhibitor add‐in rates and pH control profiles that maximize the recovery of intracellular protein. Applying the proposed approach, optimal profiles were determined such that a significant increase of the production of proteins in a fed‐batch reactor is realized. Also, the optimal control policies in a series of continuous‐flow stirred tank reactors (CFSTRs) are determined.
Production of catalytic cells for formaldehyde production and alcohol oxidase by a catabolite repression‐insensitive mutant of a methanol yeast Candida boidinii A5
Authors: Tani Yoshiki , Sawai Tohru , Sakai Yasuyoshi 
Published: December 2004

AbstractA catabolite repression‐insensitive mutant of Candida boidinii A5, strain ADU‐15, was investigated as to alcohol oxidase production and the production of cells exhibiting the maximum catalytic activity for formaldehyde production. The mutant strain ADU‐15 showed higher cell productivity and higher alcohol oxidase activity when grown on mixed substrates (glucose–methanol), especially with a high concentration of glucose in the medium. Thus, even under substrate (glucose–methanol)‐limited chemostat conditions, where the glucose concentration was low, partial derepression of alcohol oxidase by glucose in mutant strain ADU‐15 was detected. The chemostat culture conditions with the glucose–methanol medium were optimized for alcohol oxidase production and the production of cells exhibiting the maximum catalytic activity for formaldehyde production, respectively. By means of chemostat culturing on mixed substrates, we improved the alcohol oxidase productivity 5.0‐fold and the productivity of cells exhibiting the maximum catalytic activity for formaldehyde production 3.8‐fold, in comparison with the parent strain chemostat cultured with methanol as the single substrate.
Simplified models for packed‐bed biofilm reactors
Authors: Skowlund Christopher T. , Kirmse Dale W. 
Published: December 2004

AbstractFor a packed‐bed biofilm reactor two reactor models are proposed. One model is for the limiting case of a biofilm with a constant biofilm thickness in which diffusion within the biofilm is shown to be negligible. The second model assumes that the thickness of the biofilm is limited by the concentration of substrate within the biofilm. The analytical solutions for these reactor models are shown to agree very well with the numerical solutions to the exact differential equations.
Cell growth and α‐amylase production characteristics of Bacillus amyloliquefaciens
Authors: Roychoudhury Siddhartha , Parulekar Satish J. , Weigand William A. 
Published: December 2004

AbstractGrowth and α‐amylase production characteristics of Bacillus amyloliquefaciens strain F (ATCC 23350) in batch cultures are examined using glucose or maltose as the carbon source. While the cell growth is rapid when glucose is used as the carbon source, higher cell mass, higher total and specific enzyme activities, and higher enzyme production rates are obtained when maltose is used as the carbon source. The overall specific enzyme activity decreases with an increase in the initial concentration of carbon source. The oxygen requirement and carbon dioxide generation vary linearly with the maximum amount of cell mass produced. For experiments conducted using glucose as the carbon source, the kinetics of cell growth and glucose consumption are described using a special form of the Vavilin equation. For a given amount of initial carbon source, the enzyme synthesis capability is retained by the microorganism, although at a substantially reduced level, under severe oxygen limitation.