bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimal control of substrate concentrations in bioreactors with separated sensors
Authors: Oǧuztöreli M. N. , Özüm Baki , Gerson Donald F. 
Published: May 2005

AbstractMany of the sophisticated sensors desirable for monitoring bioreactors cannot be placed in the bioreactor either because they are not steam sterilizable or because they require nonphysiological operating conditions. Such sensors can be used if they are separated from the bioreactor. Separation of the sensor from the bioreactor causes a time lag in data acquisition. This results in several complexities in the development of an appropriate and stable feedback control system based on a separated sensor. This paper analyzes the optimal control of a bioreactor with a separated sensor without a time lag and analyzes the feedback control (but not necessarily the optimal control) with a time lag. Simulation results indicate that this type of analysis could be extended to more general bioreactor operating conditions.
Preparation of L‐aspartic acid by means of immobilized Alcaligenes metalcaligenes cells
Authors: Vojtšek V. , Guttrnann T. , Bárta M. , Netnral J. 
Published: May 2005

AbstractTwo types of biocatalysts based on immobilized cells of Alcaligenes metalcaligenes exhibiting aspartate ammonia‐lyase activity (EC 4.3.1.1) were developed for the enzymic preparation of L‐aspartic acid from ammonium fumarate. The first type of the biocatalyst consists in individual covalently crosslinked and permeabilized cells(I), while the second type is represented by cell aggregates (II). For the above preparation, biocatalyst I can be used only discontinuously in a mixed reactor. After termination of the reaction between individual cycles of its use, the biocatalyst is returned to the reactor in the form of a highly concentrated cell suspension or paste. Biocatalyst II can be used discontinuously or continuously in a fixed‐bed column of the catalyst. The effects of pH, substrate concentration and temperature on the reaction velocity and effectivity of enzymic conversion was investigated. Optimal parameters of the reaction are as follows: pH 8.5, initial substrate concentration, 1.35 mol/L, temperature for discontinuous process, 37°C, and temperature for continuous process, 25°C. Under these conditions the enzymic conversion of substrate to product is quantitative. Under optimal toring conditions, the specific activity of both catalysts does not change within a period of one year. The operational half‐life of the biocatalyst II during continuous use in a fixed‐bed column of the catalyst under standard reaction conditions depends on the quality of the substrate. The discontinuous preparation of L‐asparatic acid with the aid of biocatalyst I and continuous preparation of this product with the aid of biocatalyst II have been verified under pilot‐plant conditions.
INT–dehydrogenase test for activated sludge process control
Authors: Lopez Juan M. , Koopman Ben , Bitton Gabriel 
Published: May 2005

AbstractDehydrogenase activity assay of activated sludge using the redox dye 2‐(p‐iodophenyl)‐3‐(p‐nitrophenyl)‐5‐phenyltetrazolium chloride (INT) was investigated. INT‐dehydrogenase activity (INT–DHA) was directly proportional to INT dosage and inversely proportional to bio‐mass concentration over limited ranges. INT dosages exceeding 2.5m/M were toxic to dilute activated sludge suspensions. INT–DHA was greatest near pH 9, whereas the peak oxygen uptake rate (OUR) occurred at pH 8. Both INT–DHA and OUR varied inversely with sludge age, but INT–DHA was the more sensitive of the two parameters to this variable. Consistently good and highly significant correlations between INT–DHA and OUR of chlorine stressed activated sludge were found at sludge ages ranging 2.2–7.0 days.
Measuring oxygen diffusion coefficients with polarographic oxygen electrodes. II. Fermentation Media
Authors: Ho Chester S. , Ju Lu‐Kwang , Ho Chia‐Tie 
Published: May 2005

AbstractFermentation media consist of a large number of chemicals which composition undergoes alteration during the course of fermentations. In consequence, the conventional methods and correlations for gas diffusion coefficient measurement and prediction cannot be easily applied to such systems. Oxygen diffusion coefficients have been measured in simulated chemical systems as well as in complex solutions of nutrient broth, using the polarographic technique introduced in a previous article. It is identified that sugars and salts are the major factors influencing oxygen diffusion coefficients in these aqueous fermentation media. The effect of salts on oxygen diffusion coefficients in electrolyte solutions has been found to be well correlated with the square root of total ionic strength of electrolyte solutions. The individual effect of glucose and its combined effect with salts are explored in order to reach rational correlations capable of predicting oxygen diffusion coefficients in synthetic fermentation media. For aqueous solutions of glucose plus salts, it is observed that the log‐additive relationship can be used to account for the combined effect. Finally, a linear correlation has been established in measuring oxygen diffusion coefficients in aqueous solutions having different concentrations of nutrient broth.
Immobilization of Acetobacter acoti on cellulose ion exchangers: Adsorption isotherms
Authors: Bar Raphael , Gainer John L. , Kirwan Donald J. 
Published: May 2005

AbstractThe adsorptive behavior of cells of Acetobacter aceti, ATCC 23746, on DEAE‐, ECTEOLA‐, TEAE‐, and DEHPAE‐cellulose ion exchangers in a modified Hoyer's medium at 30°C was investigated. The maximum observed adsorption capacities varied from 46 to 64 mg dry wt/g resin. The Langmuir isotherm form was used to fit the data, since the cells formed a monolayer on the resin and exhibited saturation. The equilibrium constant in the Langmuir expression was qualitatively correlated with the surface charge density of the resin. The adsorption was also “normalized” by considering the ionic capacities of the resins. The exceptionally high normalized adsorption capacity of ECTEOLA‐cellulose, 261 mg dry wt/meq, may be explained by an interaction between the cell wall and the polyglyceryl chains of the exchanging groups in addition to the electrostatic effects. The effect of pH on the bacterial adsorption capacity of ECTEOLA‐, TEAE‐, and phosphate‐cellulose resins was studied and the pl of the bacteria was estimated to be 3.0.
Enzyme immobilization via monoclonal antibodies I. Preparation of a highly active immobilized carboxypeptidase A
Authors: Solomon B. , Koppel R. , Pines G. , Katchalski‐Katzir E. 
Published: May 2005

AbstractA novel method for the preparation of highly active immobilized enzymes is described. It is based on the binding of enzymes to suitable carriers via monoclonal antibodies, which bind to the enzyme with high affinity without affecting its catalytic activity. The applicability of the method forwarded has been illustrated by the preparation of two samples of highly active immobilized carboxypeptidase A (CPA) preparations as follows: A mouse monoclonal antibody (mAb 100)to CPA that binds to the enzyme with a high‐affinity constant without affecting its catalytic activity was prepared, purified, and characterized. Covalent binding of this monoclonal antibody to Eupergit C (EC) or noncovalent binding to Sepharose–protein A (SPA)yielded the conjugated carriers EC‐mAb and SPA·mAb, respectively, which reacted specifically with CPA to give the immobilized enzyme preparations EC‐mAb·CPA and SPA·mAb·CPA displaying full catalytic activity and improved stability. At pH 7.5 and a temperature range of 4–37°C an apparent binding constant of ∼108M−1 characterizing the interaction of CPA with EC‐mAb and SPA·mAb, was obtained. To compare the properties of EC‐mAb·CPA and SPA·mAb·CPA with those of immobilized CPA preparations obtained by some representative techniques of covalent binding of the enzyme with a corresponding carrier, the following immobilized CPA preparations were obtained and their properties investigated: EC‐CPA (I), a preparation obtained by direct binding of EC with CPA; EC‐NH‐GA‐CPA (II), a derivative obtained by covalent binding of CPA to aminated EC via glutaraldehyde; EC‐NH‐Su‐CPA (III), a CPA derivative obtained by binding the enzyme to aminated EC via a succinyl residue; and EC‐HMD‐GA‐CPA (IV), obtained by binding the enzyme via glutaraldehyde to a hexamethylene diamine derivative of EC. Full enzymic activity for all of the bound enzyme, such as that recorded for the immobilized CPA preparations EC‐mAb·CPA and SPA·mAb·CPA, was not detected in any of the insoluble covalently bound enzyme preparations.
Analysis and simulation of hollow‐fiber bioreactor dynamics
Authors: Kleinstreuer C. , Agarwal S. S. 
Published: May 2005

AbstractA flexible and economical computer simulation model for the process analysis, parameter prediction, and optimal design of hollow‐fiber biochemical reactors (HFBRs) has been developed. The validity and predictive capability of the HFBR simulator was successfully tested with two independent laboratory case studies. Of particular interest are the transient transport and bioconversion mechanisms including the effect of radial mass convection on the substrate uptake in the lumen. The portable computer code is an efficient tool to aid in theoretical and experimental investigations. The underlying principles used for the model development are applicable to a broad family of (membrane) bioreactors.
Determination of reactor biomass by acoustic resonance densitometry
Authors: Blake‐Coleman B. C. , Clarke D. J. , Calder M. R. , Moody S. C. 
Published: May 2005

AbstractAcoustic resonance densitometry (ARD) is reported as a method suitable not only for precise investigations into changes of specific gravity in bioreactor media but also as a technique able to provide an accurate wide range and direct determination of cellular mass in fermentation processes. It is further shown that this method can replace present optical procedures, minimizing dilution errors and operator involvement and is suitable for development as an on‐line biomass monitoring system.
General characteristics of optimal feed rate profiles for various fed‐batch fermentation processes
Authors: Modak J. M. , Lim H. C. , Tayeb Y. J. 
Published: May 2005

AbstractGeneral Characteristics of the optimal feed rate profiles have been deduced for various fed‐batch fermentation processes by analyzing singular controls and singular arcs. The optimal control sequences depend on the shapes of the specific growth and product formation rates, μ andπ, and the initial conditions. For fed‐batch processes described by four mass balance equations, the most general optimal control sequence consists of a period of maximum feed rate, a period of minimum feed rate (a batch period), a period of singular feed rate (variable and intermediate), and a batch period. Degenerate sequences in which one or more periods are missing can result with a particular set of initial conditions. If the fermentation time is not critical, the singular control maximizes the net yield of product and only when the time is also important, it balances a trade off between the yield of product and the specific growth rate which dictates the fermentation time. With the sequence of optimal control known, the optimal feed rate profile determination is reduced to a problem of determining switching times.
Optimal substrate feeding policy for a fed batch fermentation with substrate and product inhibition kinetics
Authors: Hong J. 
Published: May 2005

AbstractThe optimal substrate feeding policy for the fed batch fermentation which is governed by product and substrate inhibited kinetics is presented. The conjunction point between nonsingular and singular arcs and the feeding policy along the singular arc are derived analytically in terms of the concentrations of substrate and product and the liquid volume. Thus, it is possible to determine the feeding rate by monitoring the state variables (i.e., closed loop control). As a specific example, an optimization study of the fed batch fermentation for ethanol production by Saccharomyces cerevisiae is presented. It is shown that the optimal feeding patterns are heavily dependent upon the initial conditions. The point selectivity provides the guideline for predicting the optimal feeding patterns and explaining the results of rigorous mathematical analysis.
Kinetic model of hydrocortisone 1‐en‐dehydrogenation by Arthrobacter globiformis
Authors: Gachok V. P. , Grytsay V. I. , Arinbasarova A. Yu. , Medentsev A. G. , Koshcheyenko K. A. , Akimenko V. K. 
Published: May 2005

AbstractA kinetic model of the hydrocortisone‐to‐prednisolone transformation by Arthrobacter globiformis is constructed using the experimental data obtained in studies of this process. Besides adequately describing experimental data, the model allows one to determine the relation between hydrocortisone oxidation and the level of endogenous substrates in bacterial cells, and the relation between the saturating concentration of hydrocortisone in the enzymic system of bacteria and the content of endogenous substrates in their cells, as well as the regulation of the transmembrane potential and the activation by the uncouplers.
Combined rapid‐steam hydrolysis and organosolv pretreatment of mixed southern hardwoods
Authors: Rughani Jagdish , McGinnis Gary D. 
Published: May 2005

AbstractVarious types of pretreatments are used for biomass conversion of woods. The major objective of most pre treatments is to increase the susceptibility of cellulose and lignocellulose material to acid and enzymatic hydrolysis. In this study, southern mixed hardwoods were pretreated by combined rapid steam hydrolysis (RASH) and organosolv methods. It was found that the major factor in the pretreatment was the RASH temperatures. The organosolv temperature had only a minor effect on the reactivity of the final product. The enzymatic rate studies indicated that the RASH process helps in increasing the accessibility of cellulose to enzymatic hydrolysis and increased the amount of soluble lignin While the organosolv process only removed solubilized lignin. Another effect of the combined treatment was the decreasing of the enzymatic rate relative to a single RASH pretreatment. All hemicellulose is lost during these pretreatments. Three alcohols (methanol, ethanol, and butanol) were studied using a combined RASH organosolv process. At lower temperatures there were small differences between the alcohols; however, at higher temperatures all alcohols were equally effective. At longer RASH times, the percentage of glucose in the final product, as well as the amount of solubilized lignin, increased. However, the longer RASH times led to a decrease in enzymatic rates, Organosolv residence time studies of 15, 30, and 45 minutes displayed little effect on the product. Various wood‐to‐solvent ratios and water‐to‐alcohol ratios had very little effect on the yield of products. The stability of RASH treated material be fore organosolv process was studied under various storage conditions. The storage conditions had no apparent effect on the product.
General theory of determining intraparticle active immobilized enzyme distribution and rate parameters
Authors: Hossain Md. M. , Do D. D. 
Published: May 2005

AbstractA general theory is presented in this article for determining the intrinsic rate constants for the main reaction and deactivation reaction, the effective diffusivity of the substrate, and the active enzyme distribution within porous solid supports from deactivation study of a continuous stirred‐basket reactor (CSBR). For the parallel deactivation five reaction kinetics are considered: (a) Michaelis–Menten, (b) substrate inhibition, (c) product inhibition (competitive), (d) product inhibition (anticompetitive), and (e) zero‐order kinetics. The experimental results of the system of hydrogen‐peroxide‐immobilized catalase on controlled‐pore glass particles are analyzed to demonstrate the application of the theory developed for parallel deactivation of active immobilized enzyme (IME). For series deactivation only first‐order kinetics is treated, and a numerical procedure is proposed to deter mine the rate parameters and the internal active enzyme distribution. The experimental data of the system of glucose‐immobilized glucose oxidase on silica‐alumina and controlled‐pore glass particles are used to verify the theory.
Plasmid stability and α‐amylase production in batch and continuous cultures of Bacillus subtilis TN106[pAT5]
Authors: Wei Daniel , Parulekar Satish J. , Stark Benjamin C. , Weigand William A. 
Published: May 2005

AbstractCell growth and enzyme (α‐amylase) production characteristics of Bacillus subtilis TN106 containing the recombinant plasmid pAT5 are investigated in batch and continuous cultures using a defined medium with glucose as the limiting nutrient. The batch culture studies demonstrate that the recombinant plasmid, reported earlier1 to be stably maintained in the host, suffers from segregational and structural instabilities. The structural instability of this strain occurred during culture storage and can be eliminated in bioreactor experiments by using a modified inoculum preparation procedure. Such elimination allows an unbiased investigation of segregational instability via continuous culture studies. Such studies conducted with this fast growing microorganism, in the absence of antibiotic selection pressure, indicate a very efficient glucose utilization (very low residual glucose concentrations) over a wide range of dilution rates (0.16 h−1 – 0.94 h−1). The nearly time–invariant and low residual glucose concentrations at each such dilution rate enable convenient estimation of growth parameters of the host and recombinant cells and frequency of segregational instability from transients in the resulting mixed cultures. The specific α‐amylase activity exhibits an inverse relationship to the specific growth rate of recombinant cells. The growth of recombinant cells is not affected by the presence of antibiotic (kanamycin). The growth advantage of host cells over recombinant cells diminishes with increasing dilution rate.
Effects of reactant heterogeneity and mixing on catabolite repression in cultures of Saccharomyces cerevisiae
Authors: Fowler J. D. , Dunlop E. H. 
Published: May 2005

AbstractAn experimental study was conducted into the effect of reactant heterogeneity on glucose‐fed continuous cultures of S. cerevisiae, The heterogeneity was altered by varying mixing intensity in the nutrient entry region within a static mixing device. Experimental results confirm simulation predictions based upon a simple growth model, showing that mixing in the entry region can govern macroscopic culture behavior. Specifically, at high dilution rates, the biomass concentration was reduced by mixing patterns that increased the size of regions where glucose exceeded the threshold for catabolite repression. Because the size of such repressive regions is not uniquely determined by reactant segregation, the authors argue that in biological systems (and others involving a threshold response) an alternative measure of mixing quality should be used. Conclusions are drawn concerning the simulation of biological reactors for design purposes, and the importance of nutrient delivery systems to reactor performance.
Membranes and bioreactors: A technical challenge in biotechnology
Authors: Belfort Georges 
Published: May 2005

AbstractIntegrating the properties of synthetic membranes with biological catalysts such as cells and enzymes forms the basis of an exciting new technology called membrane bioreactors. The impetus behind this marriage comes from the recent spectacular advances in recombinant DMA and cell fusion technologies and the need to develop competitive bioprocessing schemes to produce complex and active biological molecules. The advantages and limitations of using membrane bioreactors for entrapping whole cells and enzymes are reviewed. Various membrane configurations such as microcapsules, hollow fibers, and flat sheets are compared. Several different entrapped membrane bioreactors, including single, laminated and microporous, for the conversion of optically active enantiomers are described. As with new and exciting technologies, the future of membrane bioreactors in biotechnology will depend on their ability to produce desired molecules at competitive costs.
FIA for on‐line monitoring of important lactic acid fermentation variables
Authors: Nielsen J. , Nikolajsen K. , Villadsen J. 
Published: May 2005

AbstractAn automated system with semi on‐line monitoring of glucose, lactic acid, protein, and optical density during lactic acid fermentations, is set up to study the dynamics of lactic acid bacteria. The analyzers for glucose, lactic acid, and protein are based on flow injection analysis (FIA). The system consists of a laboratory fermentor with a continuous withdrawal system and an analysis system where glucose, lactic acid, and protein concentration are measured together with the optical density of the fermentor sample. The system is controlled by a personal computer.The system response is fast, and it yields a large number of reliable and precise analytical data, whoch is of great importance for mathematical model building. Some premliminary results are shown.
Oscillations in continuous cultures of microorganisms: Criteria of utility of mathematical models
Authors: Ivanitskaya J. G. , Petrikevich S. B. , Bazykin A. D. 
Published: May 2005

AbstractThis article proposes a new approach to the modeling of continuous cultures of microorganisms based on the concept of universality classes. Instead of analysis of concrete sets of equations, vast classes including models with identical qualitative features should be studied. The class of models of the second order is the simplest one, and it is analyzed in order to demonstrate the mathematical methods used. The authors have shown that the simplest model usually used for the description of continuous cultures is sensitive to even slight modifications. The modified model changes its properties and gives rise to a class of models that are applicable to the description of damped and nondamped oscillations of biomass and substrate concentrations in a fermenter. Irrespective of the mode of the initial model modification, the oscillations have a number of common features. These features can be used as the criteria of utility of this class of models for simulation of culture behavior. Two models of the class in question (with nonzero maintenance coefficient and nonconstant yield) are analyzed using these criteria.