bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological method for protection of 6‐position of sucrose and its use in synthesis of disaccharide high‐intensity sweetener
Authors: Jones Joan D. , Hacking Andrew J. , Cheetham Peter S. J. 
Published: December 2004

AbstractA general method for protecting the 6 primary hydroxyl position of sucrose is described. It involves the production of glucose‐6‐acetate by fermentation of glucose using a strain of Bacillus megaterium followed by conversion to sucrose‐6‐acetate as a kinetic product using a specially selected fructosyl transferase producted by a newly isolated strain of Bacillus subtilis. The sucrose‐6‐acetate was found to be more lipophilic than expected, and this property aided its purification by chromatography. Pure sucrose‐6‐acetate may then be chlorinated and subsequently deacetylated to give the high‐intensity sweetener 4,1′,6′‐trichlo‐4,1′,6′‐trideoxygalactosucrose (sucralose) in high yields. This process involves fewer steps than are required for chemical synthesis using trityl chloride and acetic anhydride. Related intensely sweet molecules which were synthesized by similar methods included 4,1′,6′‐trichloro, 4,1′,6′‐trideoxy L‐arabinosucrose, and 4,1′,6′‐trichloro‐4,6,1′,6′‐tetradeoxy‐galactosucrose. They were obtained from xylose and 6‐deoxyglucose, respectively, via the intermediates xylsucrose and 6‐deoxysucrose, formed by the reaction of the fructosyl transferase on the monosaccharide acceptors.
The use of lactate dehydrogenase (LDH) release kinetics for the evaluation of death and growth of mammalian cells in perfusion reactors
Authors: Wagner A. , Marc A. , Engasser J. M. , Einsele A. 
Published: December 2004

AbstractA general methodology is proposed to estimate the actual specific growth and death rate of mammalian cells in continuous perfusion reactors from the monitoring of the release of the cytoplasmic enzyme lactate dehydrogenase (LDH) in the culture medium. The procedure is illustrated on a perfusion culture of human tumor kidney cells growing on microcarriers and producing prourokinase (PUK). The intracellular LDH content of living attached cells is checked to be constant during the culture. However, cells detached from the microcarriers, and counted dead because of the uptake of trypan blue, have only released part of their intracellular LDH. In the culture medium, LDH is relatively stable as the loss of activity does not exceed 5% per day. The time variation of the LDH concentration in the medium is used to calculate the total amount of lysed and actually produced cells in the reactors, hence, the actual specific rates of cell growth and death. It is thus found that the stationary phase observed after 400 h of perfusion culture is the result of equal growth and death rates, with a daily renewal of living cells on the microcarriers near 10%. Moreover, for the cell line tested, the production of PUK is associated with cellular growth.
Organic solvents strip water off enzymes
Authors: Gorman Lu Ann S. , Dordick Jonathan S. 
Published: December 2004

AbstractExchange of enzyme‐bound H2O with T2O in aqueous solution followed by freeze drying provided tritiated water bound to chymotrypsin, subtilisin Carlsberg, and horseradish peroxidase. The desorption of T2O from these enzymes suspended in various organic solvents showed that all three enzymes lost enzyme‐bound water with peroxidase losing the most T2O of the three in solvents of moderate to high polarity. Polar solvent resulted in the highest degree of T2O desorption (e.g., methanol desorbed from 56%‐62% of the bound T2O), while nonpolar solvents resulted in the lowest degree of desorption (e.g., hexane desorbed from 0.4%–2% of the bound T2O). Desorption is nearly immediate with most of the desorbable T2O being released from the enzymes within the first 5 min. Both solvent dielectric and a measure of the saturated molar solubility of water in a given solvent provide accurate correlations between the properties of the organic solvents and the extent of T2O desorption. This investigation shows that water stripping from an enzyme into a nonaqueous medium does occur and can be significant in polar solvents.
Hydrolysis of lactose in skim milk by immobilized β‐galactosidase (bacillus circulans)
Authors: Bakken Andrew P. , Hill Charles G. , Amundson Clyde H. 
Published: December 2004

AbstractA novel chemical reactor, consisting of β‐galactosidase from Bacillus circulans immobilized onto a ribbed membrane made from polyvinylchloride and silica, was used to hydrolyze the lactose constituent of skim milk. Multiresponse nonlinear regression methods were employed to determine the kinetic parameters of rate expressions based on a proposed enzymatic mechanism that includes the formation of oligosaccharides. High‐performance liquid chromatography (HPLC) methods were employed to monitor the concentrations of all species present in the effluent stream. For the experimental conditions used in this research, rate expressions which include the formation of trisaccharides, the inhibition effects of both the α and β anomers of galactose, and the corresponding mutarotation reaction are sufficient to model the reaction network.
Cell immobilization using PVA crosslinked with boric acid
Authors: Wu Kuo‐Ying Amanda , Wisecarver Keith D. 
Published: December 2004

AbstractA new cell immobilization technique is described in which polyvinyl alcohol is crosslinked with boric acid, with the addition of a small amount of calcium alginate. The presence of the calcium alginate improves the surface properties of the beads, preventing agglomeration. A pure culture of phenol‐degrading Pseudomonas was immobilized in the PVA‐alginate beads. Phenol was successfully degraded in a fluidized bed of the beads, indicating that cell viability was maintained following the immobilization procedure. The PVA‐alginate beads proved to be very strong and durable, with no noticeable degradation of the beads after 2 weeks of continuous operation of the fluidized bed.
Control of a thiobacillus denitrificans bioreactor using machine vision
Authors: Camp Carl E. , Sublette Kerry L. 
Published: December 2004

AbstractA PC‐based machine vision system has been used to continuously monitor changes in biomass concentration and to control the undesirable production of colloidal elemental sulfer (a reactor upset condition due to an excessive concentration of inhibitory sulfide substrate) in a bioreactor containing Thiobacillus denitrificans. A field of view of a video camera was established which contained regions of different background lighting. Mean values of the distribution of red, green, and blue intensity components within corresponding regions of a digital image image captured from the camera were used to monitr color changes associated with changes in biomass concentration, and to determine if the reactor was in an upset condition. The ration of red to blue intensity components was an important parameter in detecting the formatin of an elemental sulfur precipitant. Using a stepper motor‐driven pressure regulator, intelligent process control was performed by altering the hydrogen sulfide feed flow rate setpoint on the vision system measurements.
Fed‐batch culture automated by uses of continuously measured cell concentration and culture volume
Authors: Yamane Tsueno , Hibino Wataru , Ishihara Kazuto , Kadotani Yasuyuki , Kominami Minoru 
Published: December 2004

AbstractAn automated control method of fed‐batch culture in which the nutrient feed rate was determined from continuously measured cell concentration and culture broth volume was developed. Theoretical background was elucidated, from which it was found that the method is unique in that it controls specific substrate consumption rate of the microorganism. The method was experimentally applied to the fed‐batch cultures of recombinant Escherichia coli HB101. It was observed that the specific substrate feed rate affects not only the specific growth rate but also the growth yield. If some conditions are satisfied, this type of automated fedbatch culture can be applied widely to any microbial systems and seems especially useful when the culture medium is composed of natural complex nutrient(s) because their concentrations are very difficult to detect and control.
Extractive lactic acid fermentation using ion‐exchange resin
Authors: Srivastava Aradhana , Roychoudhury Pradip K. , Sahai Vikram 
Published: December 2004

AbstractLactic acid fermentation is an end‐product‐inhibited reaction. The restriction imposed by lactic acid on its fermentation can be avoided by extractive fermentation techniques. Studies were performed by attaching an ion‐exchange resin packed column with a 2‐L fermentor for separation of lactic acid. The fermentation, in a conventional batch mode, resulted in a lactic acid yield of 0.828 g · g−1 and a lactic acid productivity of 0.313 g · L−1 · h−1. However, these could be further enhanced to 0.929 g · g−1 and 1.665 g · L−1 · h−1 by extractive fermentation techniques. The effect of temperature on extractive fermentation was remarkable and has been included in this work.
Kinetics of enzymatic degradation of cyanide
Authors: Basheer S. , Kut Ö. M. , Prenosil J. E. , Bourne J. R. 
Published: December 2004

AbstractCYANIDASE@ is a new enzyme preparation capable of degrading cyanide in industrial wastewaters to ammonia and formate in an apparently one‐step reaction, down to very low concentrations. This enzyme has both a high selectivity and affinity toward cyanide. A granular form of the biocatalyst was used in a recirculation fixed bed reactor in order to characterize the new biocatalyst with respect to pH, ionic strength, common ions normally present in wastewaters, mass transfer effects, and temperature. Long term stability was investigated. The kinetics of the enzymatic degradation of cyanide were studied in a batch reactor using the powdered immobilized enzyme preparation and modeled using a simple Michaelis‐Menten equation.
Random mutagenesis to enhance the activity of subtilisin in organic solvents: Characterization of Q103R subtilisin E
Authors: Economou Chariklia , Chen Keqin , Arnold Frances H. 
Published: December 2004

AbstractQ103R subtilisin E was isolated following random mutagenesis and screening for improved activity in the presence of dimethylformamide (DMF). Our goal is to identify the mechanism(s) by which amino acid substitutions can enhance enzyme activity in polar organic solvents. A quantitative framework for comparing substrate binding and catalytic activities of mutant and wild‐type enzymes in the presence and absence of DMF is outlined. Kinetic experiments performed at high salt concentration (1M KCl) reveal that the mechanism behind the Q103R variant's enhanced activity toward succinyl‐Ala‐Ala‐Pro‐Phe‐p‐nitroanilide is both electrostatic and nonelectrostatic in origin. Favorable electrostatic interactions between the negatively charged succinyl group of the substrate and the positive charge on Arg 103 are responsible for tighter substrate binding. This conclusion is supported by kinetic experiments performed on the related substrate Ala‐Ala‐Pro‐Phe‐p‐nitroanilide and the hydrolysis kinetics of the Q103E, Q103K, and Q103S variants constructed by site‐directed mutagenesis. These results highlight the importance of the choice of the substrate used to screen for improvements in catalytic activity.
Enzyme‐based strategy for toxic waste treatment and waste minimization
Authors: Smith Jeffrey M. , Payne Gregory F. , Lumpkin Janice A. , Karns Jeffrey S. 
Published: December 2004

AbstractThe increasing amounts of pesticides used throughout the world, as well as the increasingly stringent governmental regulations concerning waste disposal, mandates improved techniques of waste disposal and minimization. In this article, parathion hydrolase, an enzyme with proven effectiveness at hydrolyzing organophosphates, was used to treat a cattle dipping liquid containing the pesticide, coumaphos, which is used to kill a disease‐causing tick. Waste is generated from this process when a toxic dechlorination product of coumaphos, potasan, accumulates to concentrations hazardous to the cattle. This pesticide system was used as a model to demonstrate how enzyme technology can be applied to waste treatment and minimization. Kinetic experiments showed that the hydrolysis of the two organophosphate substrates can be modeled as first‐order reactions with identical rate constants. It was further shown that the enzyme is capable of hydrolyzing only dissolved substrates. Because of the eightfold greater solubility of potasan than coumaphos (16.9 vs. 2.2 μmol/L), it was possible to utilize the enzyme to hydrolyze potasan selectively. Thus, by limiting the amount of enzyme, it is possible to remove potasan selectively to extend the lifetime of the cattle dipping liquid, thereby reducing the amount of waste generated. Based upon experimental results, a mathematical model describing the system was developed and verified. The mathematical model was then used to simulate the ability of the enzyme to hydrolyze the total amount of organophosphates, and to degrade selectively all of the toxic potasan without a significant loss of coumaphos.
Synthesis and lysis of formate by immobilized cells of Escherichia coli
Authors: Nandi R. , Bhattacharyya P. K. , Bhaduri A. N. , Sengupta S. 
Published: December 2004

AbstractFormate hydrogenlyase (FHL) activity was induced in a strain of Escherichia coli S13 during anaerobic growth in yeast extract‐tryptone medium containing 100 mM formate. The cells obtained at the optimum growth phase were immobilized in 2.5% (w/v) agar gel when 50–60% of the whole cell FHL activity was retained. The immobilized FHL system had good storage stability and recycling efficiency. In the lysis of formate, an increase of formate concentration to 1.18M increased QH2 (initial) value of the immobilized cell, and subsequently cells, hydrogen evolution, in general, ceased after 6 to 8 of incubation, resulting in incomplete lysis of formate. Presence of small amount of glucose (28 mM) was more or less quantitatively lysed with concomitant disappearence of glucose from the medium. Synthesis of formate from hydrogen and bicarbonate solution by the immobilized cells was also characterized. Presence of glucose (10 mM) in 50 mM bicarbonate solution stimulated formate synthesis by immobilized cells. The pH optimum range, Km, and specific activity of the immobilized cells for the lysis of formate were 6.8–7.2 0.4M, and 66 mL/g cell‐h, respectively. The cells could fix hydrogen to the extent of 24.4% (w/w) of its own wet cell mass in a 72‐h reaction cycle. Potentiality of the immobilized FHL system for biotechnological exploitation was discussed.
Determination of the interparticular effective diffusion coefficient for CO2 and O2 in solid state fermentation
Authors: Auria Richard , Palacios Jorge , Revah Sergio 
Published: December 2004

AbstractA simple experimental diffusion controlled fermentor (DCF), coupled with the use of a mathematical model based on mass balance, is proposed to measure the variation of the gas (CO2 and O2) diffusion coefficients in solid state fermentation. The DCF was packed with an ion‐exchange resin impregnated with a nutritive medium and inoculated with Aspergillus niger. The growth conditions in the DCF were very similar to those found in equipment operated with convective oxygen supply. The diffusion coefficient was shown to be very dependent on the biomass concentration within the solid state fermentor, and attained values of less than 5% of the molecular diffusion in air when the biomass in the fermentor reached 27 mg dry/g dry support.
Cultivation characteristics of immobilized Aspergillus oryzae for kojic acid production
Authors: Kwak Moo Young , Rhee Joon Shick 
Published: December 2004

AbstractAspergillus oryzae in situ grown from spores entrapped in calcium alginate gel beads was used for the production of kojic acid. The immobilized cells in flask cultures produced kojic acid in a linear proportion while maintaining the stable metabolic activity for a prolonged production period. Kojic acid was accumulated up to a high concentration of 83 g/L, at which the kojic acid began to crystallize, and, thus, the culture had to be replaced with fresh media for the next batch culture. The overall productivities of two consecutive cultivations were higher than that of free mycelial fermentation. However, the production rate of kojic acid by the immobilized cells was suddenly decreased with the appearance of central cavernae inside the immobilized gel beads after 12 days of the third batch cultivation.
Effect of applied potentials on the activity and growth of Thiobacillus ferrooxidans
Authors: Natarajan K. A. 
Published: December 2004

AbstractThe effect of applied DC potentials both in the positive and negative range, on the activity and growth of Thiobacillus ferrooxidans, is discussed. In general, application of positive potentials up to +1000 mV in an acid bioleaching medium was found to be detrimental to bacterial activity, while the impression of negative potentials enhanced both their activity and growth through electrochemical regeneration of ferrous ions and an increase in the biomass. Ferrous–ferric ratios in a bioleaching medium could be monitored through Eh measurements.Among the base sulfide minerals such as pyrite, chalcopyrite, and sphalerite, sphalerite could be selectively bioleached if an impressed potential of −500 mV (SCE) could be maintained in the leaching medium. Electrochemical bioleaching tests carried out under an applied potential of −500 mV with sphalerite in the presence and absence of noble minerals such as pyrite and chalcopyrite indicated enhanced zinc dissolution with negligible copper and iron in solution. Probable mechanisms and advantages of the electrochemical bioleaching process developed in the laboratory are outlined.
Effects of glucose on the production of recombinant protein C in mammalian cell culture
Authors: Sugiura Takeyuki 
Published: December 2004

AbstractEffects of glucose on a cultured Chinese hamster ovary cell line producing recombinant human protein C were investigated. After the recombinant cells reached confluency, they were maintained in the medium containing 10% serum and different levels of glucose in either batch or daily‐exchange mode. High concentrations of glucose to the cultures yielded higher cell densities. Daily exchanges of media produced higher cell densities than the corresponding batch culture. Total protein C production per cell decreased with time in batch culture, in accordance with the declined glucose metabolism. Supplementation of the media with high levels of glucose diminished both the expression and γ‐carboxylation activities of the recombinant cells. Production of protein C persisted in daily‐exchange culture, resulting in a constant production rate of protein C. In this case again, glucose reduced the specific productivity of recombinant protein C. An apparent glucose inhibition constant was determined to be 0.11 mg/mL by Dixon plots. The ability to γ‐carboxylate recombinant protein C was also impaired at the highest level of glucose. From these results, a strategy to maximize recombinant protein C productivity is discussed.
Analysis and quantification of a mixed exo‐acting and endo‐acting polysaccharide depolymerization system
Authors: Dean Sheldon W. , Rollings James E. 
Published: December 2004

AbstractA new mathematical model has been proposed based on a model presented by Suga, van Dedem, and Moo‐Young.10 The model requires a separate differential equation for each polymeric species (differentiated by degree of polymerization) in the reaction mixture. The main contribution of this model is the incorporation of experimental molecular weight distributions as the initial conditions. These molecular weight distributional as the initial conditions were obtained using modern analytical equipment previouly unknown for this application. The equipment, SEC/LALLS, measures relative concentrations of specific molecular weight species along with the corresponding molecular weights, thus yielding (through some mathematical manipulation) the absolute concentration of each molecular weight species. The concentration at each molecular weight can then be incorporated as the initial condition for that equation. Theoretically, the system of differential equations can be solved to give a more realistic time course of reaction.Synergism between endo‐acting and exo‐acting enzymes was examined theoretically using the mathematical model. Through model predictions, it was found that synergy is based on two fundamental parameters: (1) each enzyme's activity relative to the sum of enzyme activities and, (2) overall substrate concentration relative to the exo‐acting enzyme's Michaeiis kinetic constant Km. Theoretically, synergism increases as a function of reaction time. Intermediate endo fractions (ratio of endo‐acting enzyme activity to the sum of endo‐acting and exo‐acting enzyme activity) from 0.3 to 0.7 exhibit the most synergism. Values of k[log(Km, exo/S0)] above about zero also exhibits the most synergism.An examination of experimental data obtained both by SEC/LALLS and by reducing sugar measurements shows that the model is inadequate for successfully predicting quantities associated with the substrate during reaction. This is especially true for synergism predictions. At short reaction times, the model predicts the data fairly well, but at longer times the predictions are inconsistent with experimental data. These inconsistencies may be due to complicating phenomena such as enzyme inhibitions.
Alkaloid production by plant cell suspension cultures of Holarrhena antidysenterica: I. Effect of major nutrients
Authors: Panda A. K. , Mishra Saroj , Bisaria V. S. 
Published: December 2004

AbstractThe effect of major nutrients on growth and alkaloid production by plant cell culture of Holarrhena antidysenterica was studied with a view to increasing the yield of the alkaloid conessine, a therapeutic drug used for treatment of dysentery and helminthic disorders. The studies resulted in development of a modified Murashige and Skoog (MS) medium that contained 60 mM total nitrogen with a NH4+‐to‐NO3− ratio of 5:1, 0.25 mM phosphate, and 40 g/L sucrose. The growth regulators 2,4‐dichlorophenoxy acetic acid (2,4‐D) and kinetin (Kn) were also found to affect the synthesis of alkaloid. Using an optimal level of inoculum (3 g/L), the modified medium resulted in alkaloid synthesis of 0.66 g/100 g dry cell weight, which represented a 4.25‐fold increase over that obtained in standard MS medium.
Alkaloid production by plant cell cultures of Holarrhena antidysenterica: II. Effect of precursor feeding and cultivation in stirred tank bioreactor
Authors: Panda A. K. , Bisaria V. S. , Mishra Saroj 
Published: December 2004

AbstractPrecursor feeding strategy for increasing the yield of conessine, a steroidal alkaloid of Holarrhena antidysenterica, was established in cell suspension culture. A total of 50 mg/L added cholesterol was converted into 43 mg/L of alkaloid, 90% of which constituted the conessine. By applying the precursor feeding policy to the cell suspension culture in modified Murashige and Skoog (MS) medium, a total of 143 mg/L of alkaloid was produced in 8 days. In this way the alkaloid content of the cells was increased more than six times compared to that obtained in the standard MS medium. The steps leading to biotransformation of cholesterol into alkaloids were unaffected by phosphate. The shake flask data were successfully transferred to a bench scale 6‐L stirred tank bioreactor in which the specific biosynthetic rate of alkaloid production was 110 mg/100 g dry cell weight per day, about 160 times higher than that of whole plant.