bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic and thermal characteristics of enzyme–graft copolymers
Authors: Cremonesi P. , D'Angiuro L. 
Published: December 2004

AbstractThe characteristics of horseradish peroxidase (HRP) immobilized onto Sepharose by a photochemical‐initiated graft copolymerization are presented. Active copolymers were synthesized using different amounts of glycidylmethacrylate (GMA), bisacryloylpiperazine (BAP), or 1,3,5‐hexhydrotriacryloyl‐s‐triazine (HTsT) as functional monomer. The activities, the K′m values (pGMA) copolymers: 0.53–0.76 × 10−4M; pBAP copolymers: 0.90–1.4 × 10−4; pHTsT copolymers: 1.8–2.6 × 10−4M and the thermal stabilities of the enzyme copolymers were strictly connected to the type of polymer. By varying the polymer amount present in a given copolymer, significant differences were found in the thermostability properties of pBAP and pHTsT copolymers both when checked in water or in phosphate buffer. No differences were found for pGMA copolymers. The samples in which there are the lowest pBAP or pHTsT content resulted the most stable. The activity retained after 240 min at 60°C by free HRP and pGMA–HRP was 30% whereas by pBAP–HRP and pHTsT‐HRP it was 50 and 75% of the original. Operational stability of the materials was in agreement with thermostability data. These results are discussed in terms of enzyme microenvironment which is strongly affected by the different network of the three polymers.
The use of the inverted linear model of enzyme decay to plan a strategy for enzymatic batch reactions and to assess the industrial applicability of immobilized enzyme preparations
Authors: Cardoso J. P. , Costa M. C. 
Published: December 2004

AbstractThis article is concerned with the development of a model to plan a strategy for an enzymatic batch process where enzyme is subjected to deactivation described by the inverted linear decay model. The particular system studied is the enzymatic hydrolysis of penicillin to 6‐amino penicillanic acid (6 APA), but the model can be utilized with other batch systems as long as the decay of the immobilized enzyme (IME) preparation is described by the inverted linear decay model. The model developed is eminently practical and simple and several example of its application are shown. Experimental data obtained in a small pilot plant batch recirculated reactor on the average are well fitted by this model. For IME systems whose decay is best described by the first‐order decay model, it is not possible to use the same approach.
Methanol bioconversion by Butyribacterium methylotrophicum—batch fermentation yield and kinetics
Authors: Datta Rathin , Ogeltree Jacqueline 
Published: December 2004

AbstractButyribacterium methylotrophicum is an anaerobic bacterium that can convert methanol to butyrate. This ability to produce longer‐chain carbon compounds from C1 substrates could be of commercial significance. The fermentation rates and product formation depend on the methanol/bicarbonate ratios during fermentation. The kinetics of batch fermentation fit the Luedeking‐Piret model with growth and maintenance associated product formation. Butyrate yield of 0.256 mol/mol methanol (ca. 85% of theoretical yield) has been obtained in batch fermentation.
Bioconversion of cellulose into ethanol by Clostridium thermocellum—product inhibition
Authors: Kundu S. , Ghose T. K. , Mukhopadhyay S. N. 
Published: December 2004

AbstractDirect anaerobic bioconversion of cellulosic substances into ethanol by Clostridium thermocellum ATCC 27405 has been carried out at 60°C and pH 7.0 (initial for 100 L) under continuous sparging of oxygen free nitrogen in a culture vessel. Raw bagasse, mild alkali‐treated bagasse, and solka floc were used as substrates. The extent of conversion of raw bagasse (cellulose, 50%; hemicellulose, 25%; lignin, 19%) was observed as 52% (w/w) and 79% (w/w) in the case of mild alkali and steam‐treated bagasse (cellulose, 72%; hemicellulose, 11%; lignin, 12%), respectively. Use of bagasse concentration above 10 g/L showed a decreased rate in ethanol production. An inoculum age between 28–30 h and cell mass content of 0.027–0.036 g/L (dry basis) were used. The results obtained with raw and pretreated bagasse have been compared with those of highly pure Solka Floc (hemicellulose, 10%). Studies on the product inhibition indicated a linear fall of the percent of survivors with time. An Arrhenius type correlation between the cell decay rate constant and the product concentration was predicted. Even at low levels, the inhibitory effects of products on cell viability, the specific growth rate, and extracellular cellulase enzyme were observed.
Current practice in designing bottom‐entering fermentor drives
Authors: Wilson J. D. , Andrews T. E. 
Published: December 2004

AbstractTop entering drives have become almost traditional for fermentor applications, however bottom entering drives have distinct features that merit consideration. The prinicipal advantages of bottom drives are delineated and design criteria discussed. Illustrations based on experience with several hundred fermentors ranging in power from fractional to 100 HP and in scale from 10 to 30,000 gallons are presented. Specific areas dealt with include configuration, alignment, seals, and shaft design.
Mass‐energy balance for microbial product synthesis—biochemical and cultural aspects
Authors: Minkevich I. G. 
Published: December 2004

AbstractInterrelations between the rates of the product synthesis, cell biomass growth, respiration, and organic substrate consumption have been studied by the mass‐energy balance method. This method is based on the utilization of a special unit of substance reducity, namely redoxon. Biochemical parameters have been found which are involved in these interrelations and which describe the processes of high‐energy bond gain and energy expenditure during metabolism. In order to find these, the separation of the whole metabolism into several partial metabolisms has been applied. Equations have been obtained describing the dependences of the product yield and process specific productivity on the biochemical parameters and two macroscopic rates (e.g., rates of dilution and substrate consumption). Both aerobic and anaerobic product syntheses have been considered. The estimate of the upper limit of process productivity has been obtained. Mechanisms of the influence of the producer's intracellular characteristics on the rates of physiological processes and the culture productivity are discussed.
Analysis of protein distribution in budding yeast
Authors: Alberghina Lilia , Mariani Luigi , Martegani Enzo , Vanoni Marco 
Published: December 2004

AbstractFlow cytometry is a fast and sensitive method that allows monitoring of different cellular parameters on large samples of a population. Protein distributons give relevant information on growth dynamics, since they are related to the age distribution and depend on the law of growth of the population and the law of protein accumulation during the cell cycle. We analyzed protein distributions to evaluate alternative growth models for the budding yeast Saccharomyces cerevisiae and to monitor the changes in population dynamics that result from environmental modifications; such an analysis could potentially give parameters useful in the control of biotechnological processes. Theoretical protein distributions (taking into account the unequal division of yeast cells and the exponential law of protein accumulation during a cell cycle) quantitatively fit experimental distributions, once appropriate variability sources are introduced. Best fits are obtained when the protein threshold required for bud emergence increases at each new generation of parent cells.
Effect of immobilization on stability and kinetic properties of α‐L‐fucosidase from Turbo cornutus
Authors: Cohenford Menashi A. , Urbanowski Joseph C. , Dain Joel A. 
Published: December 2004

AbstractAn amount of α‐L‐fucosidase from T. cornutus liver was copolymerized with glutaraldehyde using bovine serum albumin as the carrier protein. The properties of the native, the soluble enzyme polymer complex, and the insoluble enzyme polymer complex were studied and compared under various conditions of pH, temperature, substrate, and inhibitor concentration. Native α‐L‐fucosidase was heat labile and lost more than 85% of its activity when incubated at 55°C for 5 min. In contrast, under equivalent incubation conditions, both the soluble and the insoluble enzyme polymer complexes exhibited enhanced resistance to thermal inactivation and after 5 min lost only 65 and 40% of their original activity, respectively. Polymerzation also resulted in the shift of pH optima towards the acidic range, a decrease in activation energy and a change in the apparent Km values towards the p‐nitrophenyl‐α‐L‐fucopyranoside substrate.
Dependence of biological treatment rate on species composition in activated sludge or biofilm. I: A biological treatment model with ecosystem adaptation
Authors: Vavilin V. A. , Vasiliev V. B. 
Published: December 2004

AbstractA biological treatment model with ecosystem adaptation (ESA model) is proposed as a means of describing multicomponent sewage treatment. The distribution of microorganisms which oxidize different components of the pollutant is strongly dependent on organic loading. The model can be used to compute multistep treatment systems with specific microflora at each step.
Theory and modelling of ethanol evaporative losses during batch alcoholic fermentation
Authors: Williams Lynn A. 
Published: December 2004

AbstractEvaporative loss of ethanol during batch alcoholic fermentation has been modelled, employing modern concepts of kinetics and stoichiometry and the best available phase equilibrium thermodynamic data. Theoretical results demonstrate that loss is proportional to the second power of the sugar concentration utilized and that the logarithm of loss is proportional to reciprocal absolute temperature. Good agreement is demonstrated among the theory, the numerical model, and the literature results. A master correlation for predicting ethanol loss is presented.
Application of a noninhibitory growth model to predict the transient response in a chemostat
Authors: Chiam H. F. , Harris I. J. 
Published: December 2004

AbstractA method of adapting a kinetic model based on steady‐state chemostat data to predict the transient performance of a chemostat culture is presented. The proposal provides for a time delay which can be considered equivalent to a period of reduced activity of the organism subsequent to the introduction of a step change in operating conditions. The adapted kinetic model gives substantially better performance in predicting the transient response of an experimental system than the unmodified kinetic model.
Growth and phosphate uptake of a high phosphate accumulating bacterium, Arthrobacter globiformis PAB‐6 in continuous culture
Authors: Tamatani Hiroaki , Shoda Makoto , Udaka Shigezo 
Published: December 2004

AbstractA high phosphate accumulating bacterium, Arthrobacter globiformis PAB‐6, was grown in a chemostat under glucose‐limitation. Two different growth patterns at steady state with various dilution rates were obtained. In one case, cells having a coccus shape tended to washout at a low dilution rate, 0.2 (h−1). In another, cells with a rod shape grew faster and gave a good steady‐state growth at a dilution rate of 0.4. Such a close relationship between growth rate and cell morphology was found both in continuous and batch cultures. The amount of phosphate uptake per cell mass was almost constant irrespective of the dilution rate, but the rate of the uptake was maximum at about the dilution rate of 0.4. A clone of PAB‐6 was isolated from the continuous culture with high dilution rate and had maximum specific growth rate of 0.7 in a simple glucosesalt medium.
The kinetics of penicillin‐V deacylation on an immobilized enzyme
Authors: Haagensen P. , Karlsen L. G. , Petersen J. , Villadsen J. 
Published: December 2004

AbstractAn immobilized Penicillin‐V‐acylase (commercial name, Novozym 217) with high specificity for the phenoxyacetyl‐(V)‐ side chain was investigated in a recycle reactor and in a batch reactor to find the enzymatic reaction rate as a function of conversion, x, substrate concentration, c and pH. The reaction rate depends strongly on pH, and both products, phenoxy‐acetic acid and 6‐APA, inhibit the reaction. Nonspecific side reactions amount to only a few per cent when c <150mM and pH& gt; 6.5. The effectiveness factor for commercial‐size particles is found to be about 0.65, and a value of 1.3mM is obtained for the equilibrium constant, Keq, of the deacylation reaction. A kinetic model for the deacylation process which includes the effect of pH and of the reverse (acylation) reaction is proposed. Rate data for particles of different size are fitted to the nonlinear model. Five kinetic parameters and an effective diffusivity for the immobilized enzyme particles are determined.
The fission yeast Schizosaccharomyces pombe in continuous culture
Authors: Vraná Dagmar 
Published: December 2004

AbstractThe fission yeast Schizosaccharomyces pombe was cultivated in a chemostat at dilution rates of D = 0.03, 0.05, 0.10, and 0.20 h−1. After steady state had been reached, the amount of dry matter, number of cells, concentration of residual sugar, yield coefficient (Y), and some morphological properties of the cells were estimated. Curves reflecting the dry mass, number of cells, and cell mean volume show a changing coordination between the growth rate and the rate of cell division, with respect to D. In addition, it could be concluded that in dividing cells the cell septum is localized asymmetrically; Two nonidentical cells differing both in length and volume result. The degree of asymmetry is a function of the dilution rate.
The role of chitin in uranium adsorption by R. arrhizus
Authors: Tsezos Marios 
Published: December 2004

AbstractIn order to further refine and support the uranium biosorption mechanism hypothesis proposed for Rhizopus arrhizus, uranium competitive equilibrium uptake isotherms by chitin were determined at two different solution pH levels and in the presence of different concentrations of competing ions, namely, Cu2+, Zn2+, and Fe2+. The co‐ion effect became more poronounced as the co‐ion concentration in solution and pH increased. Obtained equilibrium data are in agreement with uranium biosorption data reported earlier. Infrared, mass, and electron paramagnetic resonance (EPR) spectra of chitin before and after uranium uptake in the presence of the competing ions Cu2+, Zn2+, and Fe2+ were recorded. The combination of the spectral data and the information from equilibrium studies supported the hypothesis advanced earlier on the mechanism of uranium uptake by R.arrhizus. In addition, the data suggested the participation of a free radical in uranium coordination by the cell wall chitin. The mechanism of reduction of the uranium uptake capacity of the biomass in the presence of competing ions was also elucidated further.
Alkali treatment of corn stover to improve sugar production by enzymatic hydrolysis
Authors: MacDonald Douglas G. , Bakhshi Narendra N. , Mathews Joseph F. , Roychowdhury Anjali , Bajpai Pratima , Moo‐Young Murry 
Published: December 2004

AbstractAlkali treatment of corn stover improves the avaliability of cellulose and hemicellulose for enzymatic attack. Treatments were carried out for 1 to 60 min at temperatures and NaOH concentrations ranging from 100 to 150°C and 0 to 2%, respectively. Solubilization of the stover and sugar production by enzymatic hydrolysis (Trichoderma viride cellulase) of the solid residue and the dissolved solids were used to measure the effect of caustic treatment. At 150°C and 2% NaOH concentration, 65% of the original stover was dissolved after 5 min and 52% saccharificatin (g sugar/g stover) of the residue and dissolved solids by enzymatic hydrolysis was achieved compared to 20% for untreated corn stover.
Stopped‐flow kinetic studies of the cellulase‐catalyzed conversion of cellulose to glucose
Authors: Banerjee D. K. , Laidler K. J. 
Published: December 2004

AbstractThe kinetics of the cellulase‐catalyzed conversion of soluble cellulose into glucose have been studied over a range of substrate concentrations and temperatures, and at pH values ranging from 4.75 to 7.0. Lineweaver‐Burk plots were linear and led to V = 6.2μM/s and Km = 13.1 mM at pH 5.8 and 25.0°C. The pK values corresponding to the free enzyme are 4.8 and 6.8 and are consistent with carboxyl and imidazole groups as the active ionizing species. These pK values were little changed in the enzyme‐substrate intermediate that reacts in the ratedetermining step, suggesting that the ionizing groups are still free in this intermediate. The activation energy corresponding to V/Km is 80.6 kJ/mol, and that corresponding to V is 38.7 kJ/mol. The corresponding entropies of activation are 21 J K−1 mol−1 and –157 J K−1 mol−1, respectively.
Properties and application of immobilized β‐D‐glucosidase coentrapped with Zymomonas mobilis in calcium alginate
Authors: Lee James M. , Woodward Jonathan 
Published: December 2004

AbstractThe enzyme β‐D‐glucosidase has been immobilized on concanavalin A‐Sepharose to give a maximum loading of 2050 units/g dry weight of support material. The immobilized β‐D‐glucosidase was also entrapped within calcium alginate gel spheres with apparently only 35% retention of activity when assayed with 10mM cellobiose. However, it was discovered that, unlike the immobilized enzyme, the entrapped immobilized enzyme was not subject to substrate inhibition up to 100mM cellobiose, suggesting that a concentration gradient of cellobiose existed between the bulk solution and the interior of the gel sphere. Thus, the activity of the entrapped immobilized enzyme was almost twice as high as that of the immobilized enzyme when assayed with 100mM cellobiose. Concanavalin A‐Sepharose‐immobilized β‐D‐glucosidase and the bacterium Zymomonas mobilis coimmobilized in calcium alginate gel spheres converted cellobiose to ethanol in both batch and continuous‐flow fermentation systems.
A new function for overall optimization of yeast production
Authors: Klibansky Miriam M. , Otero Miguel A. , González Leonel F. 
Published: December 2004

AbstractThe influence of several operating variables on the productivity and nutritional quality of Candida utilis under carbon‐limited growth conditions was studied. Four responses were analyzed: biomass yield (Y), in vitro dry matter digestibility (d), nucleic acid cotents, and protein content (P). Three operating variables were studied: dilution rate, temperature, and carbon‐nitrogen ratio in the growth medium. Correlation describing the influence of operating variables on the studied response parameters were developed. From these correlations response surfaces were drawn. A new function, α = PdY, is proposed as a more comprehensive criterion for selecting the optimal conditions under the constraint of satisfying multiple objectives. It is demonstrated to be superior to the yield coefficient alone in this respect, since it accounts for factors that are important to the nutritional aspects of the process.
The macrokinetics of an enzymatic system containing an enzyme that inactivates in the course of reaction
Authors: Sud'ina G. F. , Kobel'kov G. M. , Varfolomeev S. D. 
Published: December 2004

AbstractThe work describes the action of a heterogenous multisubstrate enzymatic system under conditions involving inactivation of the enzyme. A nonsteady‐state kinetic model has been suggested for description of the system. It has been found that the time dependence of the product flow from the membrane is a curve with a maximum which falls on a time equal to the reverse inactivation constant. It has been shown that the efficiency of such systems increases as does the time of the operation of the enzyme.
Utilization of statistics and experimental design in data collection and analysis
Authors: Solomon B. O. , Erickson L. E. , Yang S. S. 
Published: December 2004

AbstractApplication of experimental design techniques to Pirt's yield model shows that it is important to collect data at the lowest and highest specific growth rates. In the fed‐batch fermentation process, values of specific growth rate can be varied from the maximum value at the start of the process to very low values near the end of the experiment.Candida utiliswas cultivated using batch followed by fed‐batch culture with glucose as the main source of carbon and energy. Values of substrate concentration, oxygen consumption, carbon dioxide evolution, liquid volume, flow rate cell concentration, and nitrogen concentration, which was an indirect measure of biomass, were measured. Least‐squares estimates of the true biomass energetic yield and maintenance coefficient were obtained using a multivariate statistical analysis procedure referred to as the covariate adjustment procedure. Methods of selecting the best estimates using covariate adjustment are illustrated. The results show that useful parameter estimates with relatively short confidence intervals can be obtained using these statistical methods.
Kinetic studies of enzymatic hydrolysis of insoluble cellulose: Derivation of a mechanistic kinetic model
Authors: Fan L. T. , Lee Yong‐hyun 
Published: December 2004

AbstractA comprehensive mechanistic kinetic model for enzymatic hydrolysis of insoluble cellulose has been synthesized by combining models for several key aspects which have been derived independent of each other. The model takes into account the major contributing factors: the nature of the enzyme system, the structure of cellulose, and the mode of interaction between the enzyme and cellulose molecules. It consists of a set of simultaneously occurring ordinary differential equations with ten kinetic constants. All of the kinetic constants have been determined independently by carrying out critically designed experiments, and they appear in the comprehensive model without any arbitrary manipulations. The governing equations of the model have been numerically simulated by means of the computer subroutine CSMP III. The model predicts the progress of hydrolysis of cellulose over a wide range of experimental conditions and hydrolysis times reasonably well. The model can even be applied to predict the progress of hydrolysis for intensively pretreated cellulose with a minor adjustment. The applicability of the model for the actual process development is also discussed.
Substrate‐to‐biomass ratio as a process control parameter in heterogeneous populations growing on complex substrates
Authors: McLoughlin Aiden J. , Crombie‐Quilty Mary B. 
Published: December 2004

AbstractThe removal of a complex substrate bovine serum albumin (BSA) by activated sludge was examined with respect to the initial level of substrate adsorbed, the rate of substrate removal, and the induction of exoprotease (located both on the sludge matrix and in the cell‐free supernatant). The relationship of these various processes, which together make up the overall removal process, was investigated with respect to the level of substrate present expressed both per unit volume and per unit biomass. A higher degree of correlation was observed when the substrate per unit biomass (S/B) ratio was used, thus providing some basis for empirical models of the activated sludge system based on the food‐to‐microorganisms (F/M) ratio. The interaction of sludge concentration and substrate concentration, plus the fact that there is not a clear distinction, as in pure culture, between substrate and microorganisms, makes the use of models devised for pure culture questionable.