bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrodynamics and mass transfer in Aspergillus niger fermentations in bubble column and loop bioreactors
Authors: Allen D. Grant , Robinson Campbell W. 
Published: December 2004

AbstractThe influence of Aspergillus niger broth rheology, bioreactor geometry, and superficial gas velocity on the volumetric liquid phase oxygen transfer coefficient (kLaL), riser gas holdup (εGR), and circulating liquid velocity (uLR) was studied in a bubble column (BC) and two external‐circulation‐loop airlift (ECLAL) bioreactors. The results are compared to those of previous studies on homogeneous fluids and in particular with a recent study on non‐Newtonian carboxymethylcellulose (CMC) solutions conducted in the same contactors used for the A. niger fermentations. As expected from the CMC‐based studies, in the heterogeneous broths of A. niger εGR, kLaL, and uLR decreased with increasing broth apparent viscosity; εGR and kLaL decreased with increasing downcomer‐to‐riser cross‐sectional area ratio, Ad/Ar, whereas uLR increased with increasing Ad/Ar. Gas holdup data in the airlift fermentations of A. niger were well predicted by the CMC‐based correlation. However, the CMC‐based correlations produced conservative estimations of kLaL and overestimates of uLR compared to the observed values in the A. niger broths.
Intramolecular esterification by lipase powder in microaqueous benzene: Effect of moisture content
Authors: Yamane Tsuneo , Kojima Yoshikazu , Ichiryu Takayuki , Nagata Masahiro , Shimizu Shoichi 
Published: December 2004

AbstractIn view of the biochemical reaction catalyzed by enzyme powder suspended in a water‐insoluble organic solvent, an equation was derived to estimate the amount of water bound to the enzyme powder. With this equation, an apparent adsorption isotherm between free water (water freely dissolved in benzene) and bound water (water bound to crude lipase powder of Pseudomonas fluorescens) was obtained. A direct lactonization reaction (synthesis of cyclopentadenolide from 15‐hydroxypen‐tadecanoic acid) catalyzed by crude lipase powder of Pseudomonas fluorescens was carried out batchwise in microaqueous benzene at 40oC. A kinetic model of the enzymatic reversible lactonization reaction was derived, from which the effect of moisture content on the initial reaction rate with a fully hydrated enzyme was mathematically expressed. The observed initial reaction rate first increased, then decreased with increasing moisture content, giving rise to the maximum rate at a certain level of the moisture content. The drop in the reaction rate at lower moisture content was due to a lesser hydration of the enzyme molecule (hydration‐limited) and the decrease in the reaction rate at higher moisture content was attributed to the dependence of the true initial rate of the reversible reaction on the moisture content (true reversible reaction limited), and could be simulated by the kinetic model. The equilibrium yield approached 100% at a lower moisture content.
Calculation of the heat of growth of Escherichia coli K‐12 on succinic acid
Authors: Battley Edwin H. 
Published: December 2004

AbstractUsing data from the literature, a method is adopted for determining the empirical composition and the unit carbon formula for dried Escherichia coli K‐12 cells by summing the quantities of C, H, O, N, P, and S in each of the major classes of macromolecular substances comprising the cellular biomass. With these data and the molar growth yield of cells on succinic acid, equations are written representing the anabolism and catabolism of E. coli K‐12 on this quantity of substrate. The enthalpy change accompanying catabolism can be calculated directly using standard enthalpies of formation because there is no term representing cellular substance. The enthalpy change accompanying anabolism is calculated to be very small or zero using microcalorimetric and other data from which the enthalpy of formation of a unit quantity of living cellular substance can be obtained. This indicates that the net enthalpy change accompanying the growth process (anabolism plus catabolism) is the same as that calculated for catabolism alone, in agreement with the same conclusion by several investigators using direct microcalorimetry. The method described here of determining the unit carbon formula and the quantity of ash remaining after cellular combustion is compared to that conventionally used in which cellular P and S is considered either to be negligible or to be a part of the ash. It is concluded that equations representing anabolism and the growth process can be written more accurately using the presently described method, leading to more accurate thermodynamic calculations.
Effect of continued exposition to ethanol on activity of the ammonium and fructose transport systems in Saccharomyces cerevisiae var. ellipsoideus
Authors: Iglesias R. , Ferreras J. M. , Arias F. J. , Muñoz R. , Girbés T. 
Published: December 2004

AbstractEthanol and cycloheximide inhibited the function of the ammonium transport system in growing cultures of Saccharomyces cerevisiae var. ellipsoideus measured as methylamine uptake. The effect was reversible with ethanol and irreversible with the antibiotic. The kinetic data are consistent with a reduction of the number of active carrier molecules located in the plasma membrane. In contrast, neither ethanol nor cycloheximide affected the specific rate of fructose uptake.
Measurement of bacterial random motility and chemotaxis coefficients: I. Stopped‐flow diffusion chamber assay
Authors: Ford Roseanne M. , Phillips Bret R. , Quinn John A. , Lauffenburger Douglas A. 
Published: December 2004

AbstractBacterial chemotaxis, the directed movement of a cell population in response to a chemical gradient, plays a critical role in the distribution and dynamic interaction of bacterial populations in nonmixed systems. Therefore, in order to make reliable predictions about the migratory behavior of bacteria within the environment, a quantitative characterization of the chemotactic response in terms of intrinsic cell properties is needed.The design of the stopped‐flow diffusion chamber (SFDC) provides a well‐characterized chemical gradient and reliable method for measuring bacterial migration behavior. During flow through the chamber, a step change in chemical concentration is imposed on a uniform suspension of bacteria. Once flow is stopped, diffusion causes a transient chemical gradient to develop, and bacteria respond by forming a band of high cell density which travels toward higher concentrations of the attractant. Changes in bacterial spatial distributions observed through light scattering are recorded on photomicrographs during a 10‐min period. Computer‐aided image analysis converts absorbance of the photographic negatives to a digital representation of bacterial density profiles. A mathematical model (part II) is used to quantitatively characterize these observations in terms of intrinsic cell parameters: a chemotactic sensitivity coefficient, μ0, from the aggregate cell density accumulated in the band and a random motility coefficient, μ, from population dispersion in the absence of a chemical gradient.Using the SFDC assay and an individual‐cell‐based mathematical model, we successfully determined values for both of these population parameters for Escherichia coli K12 responding to fucose. The values obtained were μ = 1.1 ± 0. 4 × 10−5 cm2/s and χo = 8 ± 3 ± 10−5 cm2/s. We have demonstrated a method capable of determining these parameter values from the now validated mathematical model which will be useful for predicting bacterial migration in application systems.
A new procedure for enzymatic semisynthesis of human insulin by hydrolysis of single‐chain des‐(b‐30)‐lnsulin precursor with lysyl endopeptidase
Authors: Morihara Kazuyuki , Ueno Yoshihiko 
Published: December 2004

AbstractIt has been shown that the single‐chain des‐(B‐30)‐insulin precursor (SCI) can be converted into human insulin ester by transpeptidation using trypsin in the presence of a threonine derivative. The present study demonstrates that Achromobacter lyticus protease 1 (lysyl endopeptidase) can catalyze the transpeptidation reaction more efficiently than can trypsin. It is also shown that des‐(B‐30)‐insulin (DAI) can be produced by hydrolysis of SCI with the lysyl endopeptidase. Since it is well known that SCI can be produced by gene technology, the following method is recommended for industrial production of human insulin ester: hydrolysis of SCI with lysyl endopeptidase followed by coupling of the resulting DAI with a threonine derivative using trypsin or lysyl endopeptidase.
Prediction of effects of amino acid supplementation on growth of E. coli B/r
Authors: Shu J. , Shuler M. L. 
Published: December 2004

AbstractA mathematical model for the growth of a single cell of E. coli on medium containing amino acid is presented. A mixture of purified amino acids (glutamate, aspartate, serine, tyrosine, and leucine) combined in the ratios found in a natural digest (casein) were employed as the nitrogen source. Each of these amino acids is the representative of a different family of amino acids. The transport mechanisms and assimilation routes for each amino acid were inserted into the prototype model. The enzyme activities and saturation constants used in the model were based on literature data. The maximum velocities for uptake systems were calculated from experimental data. The formation and homeostasis of amino acid pools were regulated through cross‐control of the activities of biosynthetic enzymes and of membrane transport of exogenous nutrients. The size of each amino acid pool was determined with mass balance equations that included terms for a transport system, a biosynthesis system, a transaminase enzyme system for interchange between the amino acid families, and a consumption system. The predictions of the extended model with regard to nutrient concentrations and growth rates compared well with the experimental data.
Translation of immobilized genetic information by yeast cell‐free protein synthesizing system
Authors: Kobatake Eiry , Ikariyama Yoshihito , Aizawa Masuo 
Published: December 2004

AbstractA cell‐free protein‐synthesizing system for the purpose of specific genetic information translation was constructed: ribosome, t‐RNA, and enzymes extracted from yeast cells were combined with an immobilized mRNA. The soluble fraction mixed with energy sources and amino acids was incubated with the immobilized mRNA such as poly(U), yeast mRNA, and myeloma mRNA to incorporate [3H]phenylalanine into polypeptides of de novo synthesis. By supplying amino acids to these protein‐synthesizing systems, amino acid incorporation was ascertained. Lower efficiency of the incorporation in the immobilized system than that of the homogeneous system was mainly attributed to the heterogeneous reaction where the mass‐transfer process is diffusion limited. Results obtained show the possibility of a system for specific translation of a desired genetic code.
Reaction characteristics and stability of a membrane‐bound enzyme reconstituted in bilayers of liposomes
Authors: Kheirolomoom Azadeh , Katoh Shigeo , Sada Eizo , Yoshida Ken‐Ichi 
Published: December 2004

AbstractThe effects ensuing from the interaction between membrane‐bound sarcosine dehydrogenase and the surrounding lipids as well as the effects of membrane fluidity were described in this study. A 25‐fold activation was observed upon the reconstitution of the enzyme in bilayers of SUVs made of DMPC. The considerable decrease in Km and increase in Vmax suggest the induction of favorable conformational changes in both the substrate‐binding site and the catalytic site of the enzyme due to the lipid–protein interaction. In SUVs of negatively charged phospholipids, the enzyme retained its initial activity over 1 month. The break point in the Arrhenius plot of the activity of reconstituted enzyme was found at temperatures close to the gel–liquid crystalline transition point of the phospholipid showing that the activity is sensitive to the physical state of membrane phospholipids. Further, immobilization of the reconstituted enzyme by use of ENT prepolymer resulted in a high activity, whereas no remarkable activity was detected with the immobilized enzyme without reconstitution.
Optimal nonsingular control of fed‐batch fermentation
Authors: Kurtanjek Ž. 
Published: December 2004

AbstractPresented is a new simple method for multidimensional optimization of fed‐batch fermentations based on the use of the orthogonal collocation technique. Considered is the problem of determination of optimal programs for fermentor temperature, substrate concentration in feed, feeding profile, and process duration. By reformulation of the state and control variables is obtained a nonsingular form of the optimization problem which has considerable advantage over the singular case since a complicated procedure for determination of switching times for feeding is avoided. The approximation of the state variables by Lagrange polynomials enables simple incorporation of split boundary conditions in the approximation, and the use of orthogonal collocations provides stability for integration of state and costate variables. The interpolation points are selected to obtain highest accuracy for approximation of the objective functional by the Radau–Lobatto formula. The control variables are determined by optimization of the Hamiltonian at the collocation points with the DFP method. Constraints are imposed on state and control variables.The method is applied for a homogeneous model of fermentation with volume, substrate, biomass, and product concentrations as the state variables. Computer study shows considerable simplicity of the method, its high accuracy for low order of approximation, and efficient convergence.
Absorption of CO2 in algal mass culture systems: A different characterization approach
Authors: Talbot P. , Gortares M. P. , Lencki R. W. , de la Noüe J. 
Published: December 2004

AbstractFor the characterization of CO2 absorption in aerated microalgal culture systems, a different approach based on KLa(O2) determination and transformation was studied. To confirm the validity of this method, the influence of reactions between CO2 and compounds (OH−, H2O, and NH3) present in the culture medium upon the absorption mechanism was evaluated under different physical and chemical culture conditions. Under these conditions, knowledge of the relative magnitudes of the diffusion and reaction kinetics permitted the evaluation of their relative importance. For the determination of the parameters required for the calculation of the CO2 absorption constant, empirical correlations for K and a were used that had been previously verified with experimental data for O2 absorption. Since, for the conditions studied, the absorption rate was shown to be independent of the chemical reactions taking place in the liquid phase, the KLa for CO2 could be directly related to the KLa for O2 by a simple factor that took into account the difference in aqueous diffusivity of the two gases. Thus, using methods developed for determining O2 absorption in gas–liquid contactors, it is possible to adequately characterize CO2 absorption for laboratory and pilot scale algal production systems.
Characterization of the biochemical behavior of glucose oxidase entrapped in a polypyrrole film
Authors: Fortier Guy , Bélanger Daniel 
Published: December 2004

AbstractThis article reports the characterization of the biochemical behavior of glucose oxidase entrapped in polypyrrole. The immobilization of glucose oxidase in a polypyrrole film was performed by entrapment during the electropolymerization of pyrrole at a platinum electrode poised at 0.65 V vs. SCE in aqueous solution in a one‐compartment electrochemical cell. Thin films of polypyrrole (0.11 μm) were obtained and the entrapped enzyme obeyed Michaelis kinetics, indicating no diffusional constraints of the substrate. Our results indicate that the entrapped glucose oxidase is more resistant to denaturation conditions such as alkaline pH and temperature (50 and 60°C) than the soluble form of the enzyme. The autoinactivation constant for the entrapped enzyme was also determined in presence of 0.25M of glucose and was 6.19 × 10−4 min−1, i.e., corresponding to a half‐life value of 20 h. The results reported here show clearly that polypyrrole matrix has a strong stabilizing effect on the stucture and on the activity of glucose oxidase.
Influence of pH, temperature, and inoculum composition on mixed cultures of Streptococcus thermophilus 404 and Lactobacillus bulgaricus 398
Authors: Beal C. , Corrieu G. 
Published: December 2004

AbstractThe effects of pH, temperature, and inoculum composition on Streptococcus thermophilus 404 and Lactobacillus bulgaricus 398 mixed cultures were studied. Linear quadratic models according to these three variables were proposed to express the growth and acidification characteristics, as well as the final proportion between the two strains. Initial and operating conditions, allowing maximization of these characteristics were determined. Finally, a graphic method to predict both final total concentration and final proportion of the two bacteria as a function of pH, temperature and inoculum composition is presented.
Influence of the screen material on the fouling of spin filters
Authors: Esclade Laurent R. J. , Carrel Stéphane , Péringer Paul 
Published: December 2004

AbstractMouse–mouse hybridomas (15 μm mean diameter) were cultivated in a simulated perfusion reactor with spin filter and external recirculation of the medium. Proteins at high concentrations, such as 10% foetal calf serum (FCS), were found to be not responsible by themselves for fouling, even at high recirculation rates. Stainless steel (10 μm pores) in contrast to polyamide (11 μm proes) led to a great accumulation of dead cells and nucleic acids on the screen, finally leading to fouling, as shown by biochemical and microscopic examinations. It is suggested that the high surface charge density of metals compared to polyamide is responsible for attachment of various residues. Stainless steel should rather be replaced by a resistant and nontoxic synthetic material, such as polyamide 66 which was successfully used. FCS should be avoided, since it seems to increased the fouling phenomenon. Moreover, the pore size of the screen should be carefully defined according to the wide size distribution of living and dead cells of the line used (33% of variation of the mean size in our case) as well as fragments. The purpose of the screen being to get rid of fragments and small dead cells, and not to wash too many new small cells, a good retention was achieved here by a 10‐μm opening.
Measurement and regulation of the culture reduction state in Clostridium acetobutylicum
Authors: Srivastava A. K. , Volesky B. 
Published: December 2004

AbstractWith a constant glucose feed concentration, the change in the continuous culture dillution rate resulted in an altered fermentation profile and the cellular NADH content. The cultures growing at high dillution rates demonstrated an oxidative metabolism low NADH and butanol concentrations. The low specific NADH flourescence (F/X) at high butanol production rates suggested that a rapid regeneration of NADH to NAD is essential for a high solventogenic culture activity. The culture florescence and butanol concentration remained constant in the solventogenic dilution rate range of D = 0.05–0.2 h−1 with an inverse relationship between the specific flourescence (F/X) and the specific butanol production rate, qB. Flourometric NADH observations were confirmed by enzymatic NADH determination. The stiochiometric “Fermentation Equation” was used to check the experimental data consistency and to investigate the role of the available biosynthetic and reduction energy on the culture metabolic activities under different growth conditions. The butanol concentration in the broth was stabilized in a fed‐batch process when the culture NADH fluorescence was being controlled through the addition of fresh medium.
Optimal production of glutathione by controlling the specific growth rate of yeast in fed‐batch culture
Authors: Shimizu Hiroshi , Araki Katshuiro , Shioya Suteaki , Suga Ken‐ichi 
Published: December 2004

AbstractThe optimal of the specific growth rate was obtained with simple mathematical model in a yeast fed‐batch cultures. The model was based on the mass balance around the fed‐batch system and the relationship between the specific growth rate, μ, and the specific production rate of glutathione, ρG. The optimal profile of μ was calculated as a bang–bang type, That is μ, should start from the maximum value, μmax and should be kept at μmax; then μ should be switched to μc, which gives a maximum value of ρG. It was proven from the maximum principle that switching was needed only once, with the switching time from μmax to μc depending on the final required glutathione content. Finally, this ideal profile of μ for the maximum production of glutathione was realized by manipulating the substrates feed rate in the fed‐batch culture. Using the extended Kalman filter and a programmed‐controller/feedback‐compensator (PF) system, μ could be controlled at the optimal profile obtained. As a result, the maximum production of glutathione was accomplished fairly successfully. However, further improvement in the controller performance for μ is desired. The control strategy employed here can be applied to other batch reaction processes.
Approximation of continuous growth of Cephalotaxus harringtonia plant cell cultures using fed‐batch operation
Authors: Westgate Paul J. , Curtis Wayne R. , Emery Alden H. , Hasegawa Paul M. , Heinstein Peter F. 
Published: December 2004

AbstractIn Cephalotaxus harringtonia plant cell cultures, periods of batch growth that are limited by hexose uptake are too short to make an accurate estimate of the Monod saturation constant. Continuous cultures are infeasible on a laboratory scale, and semicontinuous cultures require too frequent sampling. Fed‐batch operation, consisting of intermittent removal from a culture that is fed continuously, was investigated as a possible solution to these problems. For a constant feed rate, computer simulations showed that a steady state can be achieved which is useful for studying growth at different specific growth rates. In terms of the dilution rate it was confirmed that the operation is essentially equivalent to continuous culture when the samples represent a small fraction of the total culture volume. Experiments with glucose or fructose as the carbon source were carried out in shake flasks fed by a multichannel syringe pump. Results indicate that Monod kinetics based on medium glucose levels cannot adequately describe growth under these conditions. Monod's expression for specific growth rate using internal glucose concentration gives an improved correlation.
Two‐ and three‐phase mixing in a concentric draft tube gas‐lift fermentor
Authors: Kennard Malcolm , Janekeh Massoud 
Published: December 2004

AbstractTwo‐ and three‐phase mixing studies were carried out in a 44‐L concentric draft tube gas‐lift fermentor. It was proposed to use the fermentor for the production of solvents using immobilized bacteria. Bubble size, gas holdup, liquid velocities, circulation, and mixing times were determined for various superficial gas velocities in distilled water, starch, carboxymethyl cellulose, and ethanol solutions. The observed trends for two phase mixing were similar to other studies but the results were found to be more sensitive to liquid properties. This was possibly due to the large value of downcomer to riser area used in this study. Mixing in three phases highlighted the difficulty in predicting the effect of adding solids to the gas‐liquid system. Results showed that the gas‐lift fermentor was ideally suited to dealing with three phases but more work is necessary before accurate models can be developed to account for the effect of solids.