bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidation of an inhibitory substrate by washed cells (oxidation of phenol by Pseudomonas putida)
Authors: Sokol W. 
Published: December 2004

AbstractThe specific uptake rate of phenol by washed cells of Pseudomonas putida grown on phenol in steady‐state continuous culture at various dilution rates was studied. The Monod‐Haldane‐type equation was applied to fit the data and the best kinetic parameters were determined by nonlinear least‐squares techniques. The values of the kinetic parameters were found to increase monotonically with the phenol concentration in the original chemostat. The relations between the values of kinetic parameters and phenol concentration in the chemostat were described by empirical equations. Then the equation governing the instant uptake of phenol by microorganisms in chemostat in the high conversion range of phenol was proposed. This equation together with the mass balance equations can be used to determine the stability range of continuous stirred tank biochemical reactors (CSTBR) utilizing phenol.
Evaluation of half‐life of immobilized enzyme during continuous reaction in bioreactors: A theoretical study
Authors: Yamane Tsuneo , Sirirote Pramote , Shimizu Shoichi 
Published: December 2004

AbstractA theoretical study has been carried out on the evaluation of the apparent half‐life of immobilized enzyme activity during continuous reaction both in a plug‐flow reactor (PFR) and in a continuous‐flow stirred‐tank reactor (CSTR). Two apparent half‐lives have been defined: the elapsed time at which the feedrate becomes half of the initial one when the feedrate of the substrate solution is lowered to keep the conversion fixed (constant‐conversion policy), and the elapsed time at which the conversion becomes half of the initial one when the feedrate (or space velocity) is kept constant (constant‐feedrate policy or constant‐space‐velocity policy). Under no intraparticle diffusional limitation, the constant‐conversion policy of operation in the PFR and CSTR gives the same half‐life as that of the enzyme inactivation regardless of the formula of the reaction rate, and the constant‐feedrate policy of operation in the PFR and CSTR offers the same half‐life as that of the enzyme inactivation only when the reaction is zero‐order. Under intra‐particle diffusional limitation, apparent half‐lives are always greater than that of enzyme denaturation, depending on many factors such as order of reaction, feeding policy (constant‐conversion and constant‐feedrate policies), initial conversion, and bioreactor configuration. It is suggested to perform the continuous operation with changing feedrate to keep the conversion (or outlet substrate concentration) fixed under the domain of zero‐order kinetics so as to obtain an apparent half‐life as close to the real one in industrial operation.
Formation of oligosaccharides during enzymatic lactose: Part I: State of art
Authors: Prenosil J. E. , Stuker E. , Bourne J. R. 
Published: December 2004

AbstractEnzymatic lactose hydrolysis by β‐galactosidase (lactase) was investigated with respect to the formation of oligosaccharides. An analysis of the formation of oligosaccharides and their control is important in the development of technical applications for enzymatic lactose hydrolysis. The available literature data on transfer reactions of lactase were reviewed, compared, and presented in a concise tabular form. Mechanisms and possible ways of modelling enzymatic lactose hydrolysis, including formation of oligosaccharides, are presented.
Kinetic analysis of bioconversion of cellulose in attrition bioreactor
Authors: Jones Evan O. , Lee James M. 
Published: December 2004

AbstractThe attrition bioreactor (ABR) combines wet ball milling and enzymatic hydrolysis in one process step. It was found that the ABR did not accelerate enzyme deacti‐vation. Interfacial forces, not shear forces, caused the most deactivation. Elimination of the air–liquid interface by covering the reactor substantially increased enzyme stability. A simple exponential kinetic model was tested to predict the cellulose conversion in an ABR. Kinetic parameters were estimated from batch runs performed at various enzyme and substrate concentrations.
Escherichia coil growth dynamics: A three‐pool biochemically based description
Authors: Joshi Abhay , Palsson Bernhard O. 
Published: December 2004

AbstractA three‐pool growth model of an individual Escherichia coli cell is described herein. The model is based on a previously developed chemically structured complex single cell growth model. The reduction in model complexity and the identification of the essential modes of motion, over the time scale of growth, is achieved by temporal decomposition and analysis of hierarchy in relaxation times. The three‐pool model faithfully simulates the changes in cell size, cell shape, cell macromolecular composition, DNA initiation and termination periods, and the dependence of cell growth under abiotic glucose limitation. The predictions made by the reduced model compare favorably with both the experimental data and those of the full single cell model (SCM) without any parameter adjustments. The three‐pool model has very few significant parameters and has the potential to find immediate practical use in bioreactor design and process control strategies. The model development illustrates the use of modal analysis to yield reduced physiologically realistic dynamic model of complex microbial system such as E. coll.
In situ extractive fermentation of acetone and butanol
Authors: Roffler S. R. , Blanch H. W. , Wilke C. R. 
Published: December 2004

AbstractThe productivity of the acetone–butanol fermentation was increased by continuously removing acetone and butanol from the fermentation broth during fed‐batch culture. Whole broth containing viable cells of Clostridium acetobutylicum was cycled to a Karr reciprocating plate extraction column in which acetone and butanol were extracted into oleyl alcohol flowing counter‐currently through the column. By continuously removing these toxic metabolites from the broth, end product inhibition was reduced, and a concentrated feed solution containing 300 g/L glucose was fermented at an overall butanol productivity of 1.0 g/L h, 70% higher than the productivity of normal batch fermentation. The continuous extraction process provides flexible operation and lends itself to process scale‐up.
Influence of some physicochemical parameters on bacterial activity of biofilm: Ferrous iron oxidation by Thiobacillus ferrooxidans
Authors: Karamanev D. G. , Nikolov L. N. 
Published: December 2004

AbstractThe influence of temperature, pH, and substrate and product concentrations on the oxidation rate of ferrous iron by biofilm of Thiobacillus ferrooxidans was determined. The experiments were performed in an inverse fluidized‐bed biofilm reactor in which the biofilm thickness was kept constant at 80 μm. Oxygen concentration and diffusion through the biofilm did not limit the oxidation rate. The oxidation rate was almost unaffected by temperature between 13 and 38°C, pH between 1.3 and 2.2, ferric iron concentration up to 14 g/L, or ferrous iron concentration from 4 to 13 g/L. The kinetics of the process was described by the Monod equation with respect to the mass of the biofilm and with ferrous ions as the limiting substrate.
Hydrodynamics and oxygen transfer in pneumatic bioreactor devices
Authors: Chisti M. Y. , Moo‐Young M. 
Published: December 2004

AbstractGas holdup and oxygen transfer studies in non‐Newtonian suspensions of cellulose fibres conducted in two large (0.098 m3 each) reactors are described. Both reactors—a bubble column and a similar internal loop airlift—were unusual in that they had rectangular cross‐sections. In all cases gas holdups and kLaL declined with increasing solid concentration and, under identical conditions, the bubble column performed better than the airlift. The fluid systems used were carefully selected to represent mould fermentation broths.The behavior of true mass transfer coeffcient kL with changes in bubble size is discussed for these systems.
Restricted diffusion effect on the binding of proteins to porous polymer resins as studied by repetitive injection method
Authors: Kitano Hiromi , Nakamura Katsunori , Hirai Youhei , Kaku Takashi , Ise Norio 
Published: December 2004

AbstractA solution of bovine serum albumin (BSA) is repeatedly injected into a column packed with highly porous and hydrophobic polymer resins at appropriate intervals. The injected BSA is thoroughly retained in the column for 10 injections and, afterwards, starts to be eluted from the column gradually. Taking into consideration the restricting effect of already bound BSA upon the diffusion of newly injected BSA into the pores of the polymer resins, we can interpret the BSA elution profile from columns packed with polymer resin of various pore sizes and porosities. The effects of the binding rate constant and BSA concentration upon the elution profiles of BSA are also analyzed. Formyl groups are introduced into the polymers as a binding site with proteins, and the elution profiles of BSA from the column packed with the formylated resin are also analyzed.
Limitations of methods of determining effective diffusion coefficients in cell immobilization matrices
Authors: Itamunoala G. F. 
Published: December 2004

AbstractVarious techniques are available for determining the effective diffusivity De of solutes such as glucose in cell immobilization matrices. Nearly all, if not all, are subject to errors and limitations as regards the ranges of temperature, pressure, and/or concentration over which they give reliable results. It is the purpose of this article to compare three of these methods, designated (a) thin disc, (b) cylinder, and (c) beads types, and to show by means of a sensitivity and error analysis of the equation used in each method that the thin‐disc and cylindrical techniques give more accurate results of De than does the bead method.
Lumping analysis of biochemical reaction systems with time scale separation
Authors: Liao James C. , Lightfoot Edwin N. 
Published: December 2004

AbstractDue to the complexity of the systems, successful modelling of intracellular reaction networks must rely on lumping techniques which systematically reduce the number of variables and parameters. Fortunately, the time scale separation characteristics of biochemical systems provide opportunities for eliminating unnecessary details. Through the proper interpretation of eigenvalues and eigenvectors, this article presents a theoretical basis for systematic model reduction. Results are generalized as a semiheuristic basis for lumping systems without complete kinetic information. It is also illustrated that the simplified system can yield new insight which is otherwise unavailable.
Characterization of aqueous two‐phase systems based on polydisperse phase forming polymers: Enzymatic hydrolysis of starch in a PEG–starch aqueous two‐phase system
Authors: Larsson Mats , Mattiasson Bo 
Published: December 2004

AbstractA new method for determination of the binodial of an aqueous two‐phase system, using spectrophotometric measurements of the turbidity, is described in this article. The method is especially designed to characterize phase systems composed of polydisperse phase components. It gives information about the area representing the transition from homogeneous solution to a two‐phase system. The two‐phase systems studied were first a conventional Dextran T40‐polyethylene glycol 20M (PEG 20M) system, then a less‐well‐defined phase system based on PEG 20M and partially hydrolyzed starch. The PEG 20M‐starch system could be changed with respect to the volume ratio between the phases with time using hydrolytic enzymes, and the possibility of using the glucose released from the starch polymer is pointed out. Then the system is transformed to an extractive biconversion where the bottom phase polymer also served as the substrate.
Catalytic properties and active‐site structural features of immobilized horse liver alcohol dehydrogenase
Authors: Skerker Paul S. , Clark Douglas S. 
Published: December 2004

AbstractAlcohol dehydrogenase from horse liver was immobilized by covalent attachment to CNBr‐Sepharose and by adsorption to octyl‐Sepharose CL‐4B, a hydrophobic analog of Sepharose. In each case, rate constants for the binding and release of coenzyme and for the oxidation of substrates were measured based on the concentration of accessible active‐site zinc atoms determined by titration with a paramagnetic inhibitor. All rate constants were substantially reduced upon immobilization; however, the rate constant of immobilized enzyme for ethanol oxidation was independent of the immobilization method, whereas the rate constant for cyclohexanol oxidation was lower for enzyme immobilized to octyl‐Sepharose. Consequently, the substrate specificity of the two immobilized enzyme samples differed by an order of magnitude. Moreover, EPR spectroscopy studies and computer graphic analyses of spin labels occupying three defined regions of the active‐site domain indicated that the active‐site conformation adjacent to the catalytic zinc atom was similar in the two samples while the conformation slightly further from the zinc atom was different. This result may explain why the two immobilized enzyme preparations exhibited the same rate constant toward a small substrate (ethanol) yet different rate constants toward a larger substrate (cyclohexanol), whose rate constant is expected to be sensitive to a larger portion of the active site.
Packed‐ and fluidized‐bed biofilm reactor performance for anaerobic wastewater treatment
Authors: Denac M. , Dunn I. J. 
Published: December 2004

AbstractAnaerobic degradation performance of a laboratory‐scale packed‐bed reactor (PBR) was compared with two fluidized‐bed biofilm reactors (FBRs) on molasses and whey feeds. The reactors were operated under constant pH (7) and temperature (35°C) conditions and were well mixed with high recirculation rates. The measured variables were chemical oxygen demand (COD), individual organic acids, gas composition, and gas rates. As carrier, sand of 0.3–0.5 mm diameter was used in the FBR, and porous clay spheres of 6 mm diameter were used in the PBR. Startup of the PBR was achieved with 1–5 day residence times. Start‐up of the FBR was only successful if liquid residence times were held low at 2–3 h. COD degradations of 86% with molasses (90% was biodegradable) were reached in both the FBR and PBR at 6 h residence time and loadings of 10 g COD/L day. At higher loadings the FBR gave the best performance; even at 40–45 g COD/L day, with 6 h residence times, 70% COD was degraded. The PBR could not be operated above 20 g COD/L day without clogging. A comparison of the reaction rates show that the PBR and FBR per formed similarly at low concentrations in the reactors up to 1 g COD/L, while above 3 g COD/L the rates were 17.4 g COD/L day for the PBR and 38.4 g COD/L day for the FBR. This difference is probably due to diffusion limitations and a less active biomass content of the PBR compared with the fluidized bed.The results of dynamic step change experiments, in which residence times and feed concentrations were changed hanged at constant loading, demonstrated the rapid response of the reactors. Thus, the response times for an increase in gas rate or an increase in organic acids due to an increase in feed concentration were less than 1 day and could be explained by substrate limitation. Other slower responses were observed in which the reactor culture adapted over periods of 5–10 days; these were apparently growth related. An increase in loading of over 100% always resulted in large increases inorganic acids, especially acetic and propionic, as well as large increases in the CO2 gas content. In general, the CO2 content of the gas was very low, due to the large amount of dissolved CO2 that exited with the liquid phase at low residence times. The performance of the FBR with whey was comparable to its performance with molasses, and switching of molasses to whey feed resulted in immediate good performance without adaptation.
Preparation of polyelectrolyte‐coated pH‐sensitive poly(styrene) microcapsules and their application to initiation‐cessation control of an enzyme reaction
Authors: Kokufuta Etsuo , Shimizu Noboru , Nakamura Isei 
Published: December 2004

AbstractPoly(styrene) microcapsules, prepared by depositing the polymer around emulsified aqueous droplets, were coated with a synthesized polyelectrolyte; i.e., copolymer of maleic acid (MA) with methyl vinyl ether (MVE), co‐poly(MA, MVE), or with styrene (St), copoly(Ma, St). The permeability of the capsule membrane was investigated under various pHs of the outer medium usingn‐propyl alcohol as a permeant. It became apparent that either copoly(MA, St)‐ or copoly(MA, MVE)‐coated microcapsules function as a pH‐sensitive capsule. In particular, the former showed a dramatic change of the permeability in response to small differences in pH (5–6). By reference to the viscometric and electrophoretic studies of both copolymers, these were interpreted as being due to a pH‐induced alteration of the configuration of the copolymer coating on the surface of the capsule membrane. When sucrose was hydrolyzed in an aqueous suspension of the copoly(MA, St)‐coated capsules into which invertase was loaded, the hydrolytic reaction was initiated at pH 5. 5 and stopped at pH 4. 5. Such initiation‐cessation control was repeated reversibly without damaging the capsules.
External‐circulation‐loop airlift bioreactors: Study of the liquid circulating velocity in highly viscous non‐Newtonian liquids
Authors: Popović Milan , Robinson Campbell W. 
Published: December 2004

AbstractIn order to obtain further information on the behavior and optimal design of external‐circulation‐loop airlift (ECL‐AL) bioreactors, the liquid circulating velocity, gas holdup and average bubble diameter in the downcomer were studied using highly viscous pseudoplastic solutions of various types of CMC. A few comparative measurements also were made using a viscous Newtonian aqueous sucrose solution. For the liquid velocity measurements, an ultrasonic flow meter (Doppler frequency shift principle) was applied for the first time to the gas/non‐Newtonian liquid dispersion in downward flow and satisfactory results were obtained. For viscous liquids, the circulating liquid velocity in the riser section of an ECL‐AL (uLR) is shown to be dependent mainly on the downcomer‐to‐riser cross‐sectional area ratio (Ad/Ar), the effective viscosity (ηeff) and the gas superficial velocity (uGR) as described by the following equation

The circulating liquid velocity exerts opposing effects on the mass transfer and liquid‐phase mixing performances of ECL‐AL fermentors. Therefore, it is proposed that the optimum operating conditions for a given fermentation may be best achieved by means of independently regulating the circulating liquid velocity.
Improved pseudoanalytical solution for steady‐state biofilm kinetics
Authors: Sáez Pablo B. , Rittmann Bruce E. 
Published: December 2004

AbstractSimple algebraic expressions for the flux of substrate into a steady‐state biofilm are developed. This pseudoanalytical solution, which eliminates the need for repetitiously solving numerically a set of nonlinear differential equations, is based on an analysis of the numerical results from the numerical solution of the differential equations. The critical advantage of this new pseudoanalytical solution is that it is highly accurate for the entire range of substrate concentrations and kinetic parameters. The article also illustrates that previous pseudoanalytical solutions for steady‐state biofilm kinetics are seriously inaccurate for certain ranges of substrate concentration and kinetic parameters.
Extended monod kinetics for substrate, product, and cell inhibition
Authors: Han Keehyun , Levenspiel Octave 
Published: December 2004

AbstractA generalized form of Monod kinetics is proposed to account for all kinds of product, cell, and substrate inhibition. This model assumes that there exists a critical inhibitor concentration above which cells cannot grow, and that the constants of the Monod equation are functions of this limiting inhibitor concentration. Methods for evaluating the constants of this rate form are presented. Finally the proposed kinetic form is compared with the available data in the literature, which unfortunately is very sparse. In all cases, this equation form fitted the data very well.
Economic evaluation of enzymatic hydrolysis of phenol‐pretreated wheat straw
Authors: Zacchi Guido , Skoog Kerstin , Hahn‐Hägerdal Bärbel 
Published: December 2004

AbstractExperimental data from the enzymatic hydrolysis of phenol‐pretreated Swedish wheat straw have been used to evaluate the cost fractions of capital and utility, enzyme, and raw material. Two different raw material prices and varying enzyme prices have been used. The evaluation is based on an empirical model for the enzymatic hydrolysis and a computer program where utility and equipment, enzyme, and raw material prices can be varied. The optimal residence time for the enzymatic hydrolysis is in the range of 70–110 h. A fed‐batch procedure with substrate concentrations higher than 10% oven‐dried material (ODM) and enzyme concentrations in the range (6–10) · 106 FPU/ton ODM should be used.
Dearomatization of lignin derivatives by fungal protocatechuate 3,4‐dioxygenase immobilized on porosity glass
Authors: Wojtaś‐Wasilewska M. , Luterek J. , Leonowicz A. , Dawidowicz A. 
Published: December 2004

AbstractProtocatechuate 3,4‐dioxygenase (see protocatechuate: oxygen 3,4‐oxidoreductase, EC 1.13.11.3) was isolated from the mycelium of Pleurotus ostreatus (induced with p‐hydroxybenzoic acid) and immobilized on controlled porosity glass beads. Four fractions of Na–lignosulfonates (varying in Mr, after chromatography on Sephadex G‐50) were treated with the immobilized enzyme. The products after incubation showed the same Mr as the untreated fractions, but their light absorption at 280 nm considerably decreased. These studies indicate that dioxygenase causes partial dearomatization of lignin macromolecule.
Batch kinetics of microbial polysaccharide biosynthesis
Authors: Mulchandani A. , Luong J. H. T. , Leduy A. 
Published: December 2004

AbstractA modified form of logistic equation has been proposed to quantity the batch kinetics of microbial growth during the biosynthesis of extra‐ and intracellular polymers. Based on the experimental data developed in this study, the proposed model appeared to provide adequate growth and fermentation kinetics of Aureobasidium pullulans. The model was also applicable for representing the reported data on pullulan, xanthan, and poly‐β‐hydroxybutyricacid. In comparison to the logistic and Monod kinetics, this model fitted the data better and more accurately described the overall fermentation, both concentrations and fermentation time.
Ultrasound enhanced bioprocesses: Cholesterol oxidation by Rhodococcus erythropolis
Authors: Bar Raphael 
Published: December 2004

AbstractCholesterol oxidation to cholestenone by resting cells of Rhodococcus erythropolis ATCC25544 was investigated under a computer‐controlled ultrasonic irradiation at a frequency of 20 kHz. The optimization of the ultrasound intensity and its mode of application to a stirred bioreactor was first established at a level which preserved the structural integrity of the cells and enabled their metabolic activity. A significant enhancement in the kinetic rates of the biotransformation was observed in microbial slurries of 1.0 and 2.5 g/L cholesterol when sonicated for 5 s every 10 min with a power output of 2.2 W/cm2. In contrast, ultrasound had no effect on the enzymatic oxidation of cholesterol (2.5 g/L) by cholesterol oxidase. A high loading of cholesterol (5.0 g/L) in sonicated microbial systems had, however, an adverse effect. The ultrasound enhancement is discussed in terms of an increased dissolution rate of the sustrate crystals and more importantly, in terms of the uniquely ultrasound‐induced enhancement of mass transfer inside and outside a cell.