bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parametric studies of ethanol production form xylose and other sugars by recombinant Escherichia coli
Authors: Beall David S. , Ohta K. , Ingram L. O. 
Published: December 2004

AbstractThe conversion of xylose to ethanol by recombinant Escherichia coli has been investigated in pH‐controlled batch fermentations. Chemical and environmental parameters were varied to determine tolerance and to define optimal conditions. Relatively high concentrations of ethanol (56 g/L) were produced from xylose with excellent efficiencies. Volumetric productivities of up to 1.4 g ethanol/L h were obtained. Productivities, yields, and final ethanol concentrations achieved from xylose with recombinant E. coli exceeded the reported values with other organisms. In addition to xylose, all other sugar constituents of biomass (glucose, mannose, arabinose, and galactose) were efficiently converted to ethanol by recombinant E. coli. Unusually low inocula equivalent to 0.033 mg of dry cell weight/L were adequate for batch fermentations. The addition of small amounts of calcium, magnesium, and ferrous ions stimulated fermentation. The inhibitory effects of toxic compounds (salts, furfural, and acetate) which are present in hemicellulose hydrolysates were also examined.
Modeling of hollow‐fiber capillary reactor for the production of L‐Alanine with coenzyme regeneration
Authors: Fujii Tomoyuki , Miyawaki Osato , Yano Toshimasa 
Published: December 2004

AbstractContinuous production of L‐alanine with conjugated enzyme systems of alanine dehydrogenase (AlaDH) and lactate dehydrogenase (LDH) or alcohol dehydrogenase (ADH) was carried out with NAD regeneration in an ultrafiltration hollow‐fiber capillary reactor (HFCR) which was proposed as a test bioreactor with very small scale. In the AlaDH/LDH system, pyruvate is the intermediate product for L‐alanine so that an optimal point existed in pyruvate concentration for the production rate of L‐alanine. NAD cycling number of 4850 and L‐alanine productivity of 61.7 mmol/L h were obtained at the best condition. In the AlaDH/ADH system, however, the substrate inhibition in the AlaDH reaction by pyruvate should be considered and the best results of NAD cycling number and L‐alanine productivity were 2700 and 13.5 mmol/L h, respectively. In consideration of concentration distribution and mixing in the axial direction on an HFCR, performance of the reactor was theoretically analyzed with a multistage stirred tank reactor model combined with the kinetic model based on all the elementary reactions involved. Although quantitative discrepancy existed in some cases, the present theoretical model could explain experimental results and is expected to be generally applicable to standard hollow fiber reactors.
High‐density photoautotrophic algal cultures: Design, construction, and operation of a novel photobioreactor system
Authors: Javanmardian Minoo , Palsson Bernhard O. 
Published: December 2004

AbstractA photobioreactor system has been designed, constructed and implemented to achieve high photosynthetic rates in high‐density photoautotrophic algal cell suspensions. This unit is designed for efficient oxygen and biomass production rates, and it also can be used for the production of secreted products. A fiber‐optic based optical transmission system that is coupled to an internal light distribution system illuminates the culture volume uniformly, at light intensities of 1.7 mW/cm2 over a specific surface area of 3.2 cm2/cm3. Uniform light distribution is achieved throughout the reactor without interfering with the flow pattern required to keep the cells in suspension. An on‐line ultrafiltration unit exchanges spent with fresh medium, and its use results in very high cell densities, up to 109 cells/mL [3% (w/v)] for eukaryotic green alga chlorella vulgaris. DNA histograms obtained form flow cytometric analysis reveal that on‐line ultrafiltration influences the growth pattern. Prior to ultrafiltration the cells seem to have at a particular point in the cell cycle where they contain multiple chromosomal equivalents. Following ultrafiltration, these cells divide, and the new cells are committed to division so that cell growth resumes. The Prototype photobioreactor system was operated both in batch and in continuous mode for over 2 months. The measured oxygen production rate of 4‐6 mmol/L culture h under continuous operation is consistent with the predicted performance of the unit for the provided light intensity.
A novel continuous centrifugal bioreactor for high‐density cultivation of mammalian and microbial cells
Authors: Van Wie Bernard J. , Brouns Thomas M. , Elliot Michael L. , Davis William C. 
Published: December 2004

AbstractA continuous centrifugal bioreactor (CCBR), developed to study the growth and productivity of dense suspensions cultures, has been applied to both fermentation and mammalian cell cultivation processes. With this approach, high‐density nonflocculent cultures are maintained in a tapered fluidized bed by balancing the drag forces on the cells due to following substrate with the centrifugal forces. The Sysyem was first used to produce ethanol by fermentation with Saccharomyces cerevisiae; then with H21A1 mouse hybridoma cells secreting monoclonal antibody (MoAb), lgM. Results of this research show the feasibility of using the CCBR for both production of secreted products and as a research tool for studying cell metabolism and production kinetics. Media recycle may be used to modify the behavior of the system form a plug flow apparatus to a continuous stirred reactor (CSTR).
Solute exclusion from cellulose in packed columns: Process modeling and analysis
Authors: Neuman R. P. , Walker L. P. 
Published: December 2004

AbstractIn this investigation, process modeling and analysis were used to explore the behavior of solute exclusion from cellulose in packed columns. The study focused on modeling the effects of dispersion, mass transport, and pore diffusion. Three mathematical models were used to predict the behavior of the columns: an equilibrium model, a mass transfer model, and a combined mass transfer and pore diffusion model. Computer implementations of these models were tested against experimental conditions where cellulose particle size and solution velocity were used to either amplify or minimize dispersion or skewness in the elution curves. For small cellulose particles (200–300 mesh), all three models accurately predicted the shape of the elution curve and the particle porosity. For larger particles (45‐60 mesh), the mass transfer model and the combined mass and pore diffusion model best represented the behavior of the column. At high solution velocities (0.63 cm3 min−1) and large particles, only the combined mass transfer and pore diffusion model accurately represent the column behavior. Sensitivity analysis revealed that the mass transfer coefficient had little effect on the elution curves for the range of values (10−6–10−3 cm s−1) calculated from the experimental data. The combined mass transfer and pore diffusion model presented in this article can be used to design solute exclusion measurement experiments for the larger cellulose particles found in a commercial cellulose‐to‐ethanol plant.
Emulsion stability and demulsification during the direct extraction of penicillin broth
Authors: Szabó Csaba 
Published: December 2004

AbstractIn this article, we present the factors which influence the stability of the emulsion forming under the circumstances of the direct extraction of penicillin fermentation broth and the conditions of demulsification. A laboratory method has been developed for testing demulsifiers and a quantitative evaluation of the properties determining the separation of phases has been worked out as well. It has been found that an emulsion of oil in water (o/w) forms and that this is very stable; it can be broken only by the presence of demulsifier and by using a field of centrifugal force. We have discovered that the most effective demulsifiers are cation‐active surfactants for 1–4 g/L broth concentration. Furthermore, it is advantageous if the demulsifier contains a nonionic surfactant and wetting agent as well. From the 19 surface‐active compounds studied in the laboratory, we found that the NADAR 107 A and ARMOGARD D‐5306 demulsifiers contained the best properties for the extraction of the penicillin broth.
Use of glucose starvation to limit growth and induce protein production in Escherichia coli
Authors: Tunner Joseph R. , Robertson Channing R. , Schippa Serena , Matin Abdul 
Published: December 2004

AbstractThe use of glucose starvation to uncouple the production of recombinant β‐galactosidase from cell growth in Escherichia coli was investigated. A lacZ operon fusion to the carbon starvation‐inducible cst‐1 locus was used to control β‐galactosidase synthesis. β‐Galactosidase induction was observed only under aerobic starvation conditions, and its expression continued for 6 h following the onset of glucose starvation. The cessation of β‐galactosidase expression closely correlated with the exhaustion of acetate, an overflow metabolite of glucose, from the culture medium. Our results suggest the primary role of acetate in cst‐1‐controlled protein expression is that of an energy source. Using this information, we metered acetate to a glucose‐starved culture and produced a metabolically sluggish state, where growth was limited to a low linear rate and production of recombiant β‐galactosidase occurred continuously throughout the experiment. The cst‐1 controlled β‐galactosidase synthesis was also induced at low dilution rates in a glucose‐limited chemostat, suggesting possible applications to high‐density cell systems such as glucose‐limited recycle reactors. This work demonstrates that by using an appropriate promoter system and nutrient limitation, growth can be restrained while recombinant protein production is induced and maintained.
Enzymatic reaction kinetic: Comparison in an organic solvent and in supercritical carbon dioxide
Authors: Dumont T. , Barth D. , Corbier C. , Branlant G. , Perrut M. 
Published: December 2004

AbstractMyristic acid esterification has been performed by an immobilized lipase from Mucor Miehei both in n‐hexane and in supercritical carbon dioxide (SCCO2). The enzyme is stable in SCCO2 at 15 MPa and 323 K. The reaction rate is influenced by the concentration of water and by the reaction medium composition. A reaction mechanism is proposed, and kinetic parameters are determined at 12.5 MPa and 313 K. Maxium velocity appears 1.5‐fold higher in SCCO2 than in n‐hexane; however, as solubility of myristic acid is greater in n‐hexane, it is not yet definitively clear that the supercritical medium is more favorable than the classical organic solvent for this type of enzyme reaction.
Changes in yeast amino acid pool with respiratory versus fermentative metabolism
Authors: Martíez‐force Enrique , Benítez Tahía 
Published: December 2004

AbstractThe precursors of the amino acid yeast pool are intermediates of either the glycolytic or the tricarboxilic acid pathway (TCA). Accordingly, the influence of the metabolism (fermentative or respiratory) on the internal amino acid pool of the yeast Saccharmyces cerevisiae was established by measuring the intracellular amino acid concentration of the “grande” strain IF1256 and its “petite” mutant either in steady‐state or when shifting from fermentative to respiratory conditions. Under steady‐state conditions, when the cells only respire, there is a decrease in nearly all the amino acids whose precursors are intermediates of the glycolytic pathway. When the metabolism is exclusively fermentative, the opposite change takes place. This effect is not observed in those amino acids whose precursors come from the TCA cycle. However, in continuous culture and at dilution rates lower than 0.06 h−1, there is an enormous increase in the concentration of all the amino acids in both strains, whatever their precursor, whereas, in batch cultures, both strains undergo variations in the concentration of most amino acids, when entering stationary growth phase. Results therefore indicate that, the fact that the cells ferment or respire effectively affect their amino acid pool according to their precursors coming from the glycolytic or the TCA pathway, but other parameters, such as growth rate or exponential versus stationary phase, have a much stronger effect on yeast amino acid concentration. © 1992 John Wiley & Sons, Inc.
Computer‐assisted modeling of subtilisin enantioselectivity in organic solvents
Authors: Fitzpatrick Paul A. , Ringe Dagmar , Klibanov Alexander M. 
Published: December 2004

AbstractIn order to rationalize our discovery of a marked dependence of subtilisin's enantioselectivity on the organic solvent used as the reaction medium, we empolyed the X‐ray crystal structure of the enzyme and the means of interactive computer modeling to construct the structures of the reactive enzyme‐substrate complexes. For subtilisin‐catalyzed transesterifications between vinyl butyrate and S and R enantiomers of chiral secondary alcohols XCH(OH)Y, the computer simulation data clearly explain a higher reactivity of the former enantiomer on the basis of severe steric hindrances experienced by the latter enantiomer in the active site of subtilisin. The models of binding derived by computer modeling also successfully predicted changes in subtilisin enantioselectivity as a function of the sizes of the X and Y substituents in the nucleophile and upon addition of certain inhibitors. © 1992 John Wiley & Sons, Inc.
Continuous hydrolysis of olive oil by immobilized lipase in organic solvent
Authors: Yang Dongsoo , Rhee Joon Shick 
Published: December 2004

AbstractLipase (EC 3.1.1.3) from Candida rugosa was immobilized with DEAE‐Sephadex A50, Sephadex G50, Sephadex LH‐20, Amberlite IRA94, and Amberlite XAD‐7. The enzye immobilized with DEAE‐Sephadex A50 was found to be most effective for continuous hydrolysis of olive oil in isooctane. For the continuous reaction, 0.2 g of dry immobilized enzyme was swollen with predetermined amount of water, and packed in a glass column reactor. When the organic solvent (Isooctane) containing olive oil substrate was cocurrently fed with aqueous buffer, the two phases were evenly distributed throughout the packed bed without surfactant supplement or prior mixing of the two phases. A small amount of the surfactant (AOT) was used only in packing procedure, and no additional surfactant was necessary thereafter. Effects of initial water content of the swollen gel, buffer types, and strength were examined in the continuous reaction. Our results suggest that the operational half‐life was affected by desorption of the bound enzyme. Under the conditions of 20% olive oil in isooctane and 25 mM triethanolamine buffer (pH 7.0), operational half life was 220 h at 30°C. The reactor was also operable with n‐hexane, but the operational stability of the immobilized enzyme in n‐hexane was only half of that in isooctane. Our results indicate that various enzyme carrier having hydrophilic or amphiphilic properties could be used for two‐phase continuous reaction in packed‐bed column, reactor without any surfactant supply or prior dispersion of the two immiscible phases. © 1992 John Wiley & Sons, Inc.
Stimulation of acid phosphatase induction in Saccharomyces cerevisiae by electrochemical modulation of effector concentration
Authors: Haruyama Tetsuya , Kobatake Eiry , Ikariyama Yoshihito , Aizawa Masuo 
Published: December 2004

AbstractA novel modulating method of the expression of Saccharomyces PHO 5 gene, responsible for acid phosphatase (APase), is proposed. The method is based on electrochemical modulation of an effector (inorganic phosphate) concentration, as the gene expression is initiated below a threshold concentration of phosphate and is terminated above the threshold value. By positioning the yeast in the close neighborhood of a conducting polymer, the authors show the effectiveness of the electrochemical approach toward PHO 5 induction. Based on the approach, phosphate concentration is easily modulated at the boundary concentration by taking advantage of anion doping–undoping at a conducting polymer and the resulting anion localization–delocalization in the polymer, as the local enrichment of phosphate in the polymer results in the lowering of phosphate in the vicinity of polypyrrole. External phosphate concentration is thus electrochemically modulated when the conducting polymer is positioned in the close neighborhood of the yeast cells; thereby the PHO gene is induced. Here an electrochemical approach for the APase expression as a strategy of selective induction of specific genetic information is described. © 1993 John Wiley & Sons, Inc.
Kinetic study of lipase catalyzed esterification reactions in water‐in‐oil microemulsions
Authors: Stamatis Haralambos , Xenakis Aristotelis , Menge Ulrich , Kolisis Fragiskos N. 
Published: December 2004

AbstractThe kinetics of the esterification of lauric acid by (‐)menthol, catalyzed by Penicillium simplicissimum lipase, was studied in water/bis‐(2‐ethylhexyl)sulfosuccinate sodium salt (AOT)/isooctane microemulsions. Due to their low water content, microemulsions assist in reversing the direction of lipase activity, favoring synthetic reactions. The kinetics of this synthesis follows a Ping‐Pong BiBi mechanism. The values of all apparent kinetic parameters were determined. The theoretical model for the expression of enzymic activity in reverse micelles, proposed by Verhaert et al. (Verhaert, R., Hilhorst, R., Vermüe, M., Schaafsma, T. J., Veeger, C. 1990. Eur. J. Biochem. 187: 59–72) was extended to express the lipase activity in an esterification reaction involving two hydrophobic substrates in microemulsion systems. The model takes into account the partitioning of the substrates between the various phases and allows the calculation of the intrinsic kinetic constants. The experimental results showing the dependence of the initial velocity on the hydration ratio, Wo = [H2O]/[AOT], of the reverse micelles, were in accordance with the theoretically predicted pattern. © 1993 John Wiley & Sons, Inc.
Estimation of disruption of animal cells by turbulent capillary flow
Authors: Zhang Z. , Al‐Rubeai M. , Thomas C. R. 
Published: December 2004

AbstractDisruption of animal cells in turbulent capillary flows has been predicted from a model of cell–hydrodynamic interactions using cell mechanical properties determined by micromanipulation. Eddies of sizes similar to or smaller than the cells are presumed to interact with those cells, causing local surface deformations. The proposed mechanism of cell damage is that such deformations result in an increase in membrane tension and surface energy and that a cell disrupts when its bursting membrane tension and bursting surface energy are exceeded. The surface energy of the cells is estimated from the kinetic energy of appropriately sized eddies. To test the model, cells were disrupted in turbulent flows in capillaries at mean energy dissipation rates up to 2 × 104 m2/s3. In all cases the model underestimated the cell disruption by about 15%. Such good agreement implies that the approach of the model to the complicated phenomena of cell turbulence interactions is reasonable. © 1993 John Wiley & Sons, Inc.
Engineering cellulase mixtures by varying the mole fraction of Thermomonospora fusca E5 and E3, Trichoderma reesei CBHI, and Caldocellum saccharolyticum β‐glucosidase
Authors: Walker L. P. , Belair C. D. , Wilson D. B. , Irwin D. C. 
Published: December 2004

AbstractIn this study, different mole fractions of pure Thermomonospora fusca E5 and E3, plus Trichoderma reesei CBHI were studied for reducing sugar production at 2 h, degree of synergism, and cellulose binding. In addition, the effects of introducing the Caldocellum saccharolyticum β‐glucosidase into this cellulase system were investigated. The cellulases used were purified to homogeneity. Avicel PH 102 (4% w/w solution in 0.05 sodium acetate pH 5.5 buffer) was the substrate. Reactions were run at 50°C for 2 h using total cellulase concentrations of 8.3 or 12.2 μM. A bimixture of T. fusca E3 and T. reesei CBHI was very effective in hydrolyzing microcrystalline cellulose (9.1% conversion). The addition of endoglucanase E5 to the mixture only increased conversion to 9.8%. However, when both E5 and β‐glucosidase were added, conversion increased to 14%. It was also observed that increasing total cellulase concentration beyond 8.3 μM did little to increase percent conversion of cellulose into glucose. The results of the binding studies indicate no competition for binding sites between the endo‐ and exocellulases. © 1993 John Wiley & Sons, Inc.
Study on separation of conalbumin and lysozyme from high concentration fresh egg white at high flow rates by a novel ion‐exchanger
Authors: Ming Fang , Howell John , Acosta Fernando , Hubble John 
Published: December 2004

AbstractIn this report, we show that it is possible to separate valuable proteins from egg‐white using a ProductivTM CM ion‐exchanger column operated at flow rates significantly higher than those than can be achieved using traditional particulate adsorbents. In the approach taken, sample pretreatment is restricted to a simple dilution of the egg‐white, which can then be applied to the column at superficial velocities (Vs) of up to 13.8 m/h. Under a loading of 220 mg total protein per milliliter of ion‐exchanger, the resolution (Rs) between the eluted conalbumin and lysozyme fractions was found to be almost constant during nine consecutive adsorption/desorption cycles. For all nine consecutive batches, the column average adsorption capacity was greater than 30 mg/mL, with 90% recovery of adsorbed protein being achieved in each run. The overall productivity achieved was 12.6 kg/m3 h for lysozyme and 31.2 kg/m3 h for conalbumin. © 1993 John Wiley & Sons, Inc.
Stability of antibody productivity is improved when hybridoma cells are entrapped in calcium alginate beads
Authors: Lee Gyun Min , Palsson Bernhard O. 
Published: December 2004

AbstractLoss of monoclonal antibody (MAb) productivity in long‐term, free‐suspended cell culture is often attributed to the appearance of a nonproducing population of hybridoma cell (NP) in the culture which has a growth advantage over the producing population (P). However, when an NP appears in long‐term culture of entrapped cells, it may not be able to take over the whole culture in a short period of time due to the limited growth of the entrapped cells. In order to examine the hypothesis that entrapped cells can have improved stability of MAb productivity due to limited cell growth, free‐suspended cell culture and calcium alginate–entrapped cell culture with inocula consisting of a P and an NP were compared with regard to stability of MAb productivity in a repeated fed‐batch culture. In free‐suspended cell culture, the NP appeared to take over the whole culture within three batches, and thereby MAb production completely disappeared. In entrapped cell culture, an NP appeared to outgrow the P rapidly only during an exponential growth phase, resulting in a significant decrease in specific MAb productivity, qMAb, from 11.58 μg/106 cell/day to 2.76 μg/106 cell/day. However, when the cell growth was limited in entrapped cell culture, the NP no longer outgrew the P rapidly, as indicated by the stable value of qMAb. In addition, when the cells recovered from the alginate beads by citrate buffer treatment were subcultured in free‐suspended cell culture, MAb production rapidly deteriorated and completely disappeared within two batches. Thus, the P present at a small fraction of viable cell concentration in the beginning of the free‐suspended cell culture, which were previously entrapped in alginate beads, seemed to be outgrown rapidly by the NP. Taken together, the results obtained from these experiments support the hypothesis that the limited cell growth in entrapped cell culture, which keeps an NP from taking over the whole culture, is responsible, in part, for the improved stability of MAb productivity. © 1993 John Wiley & Sons, Inc.