bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cybernetic modeling of bacterial cultures at low growth rates: Mixed‐substrate systems
Authors: Turner Brian G. , Ramkrishna D. , Jansen Norman B. 
Published: December 2004

AbstractA cybernetic model to predict the low‐growth‐rate behavior of bacteria in mixed‐substrate environment is presented. Using only growth and maintenance parameters from single‐substrate experiments, the model accurately predicts the simultaneous substrate utilization and maintenance energy effects in constant fed‐batch cultures of Klebsiella oxytoca. The robustness of the model was examined more rigorously by perturbing glucose‐limited fed‐batch cultures with additions of arabinose, xylose, and fructose. In all cases, reasonable agreement of the model prediction with the experimental data was observed.
Fluorescence sensing of fermentation parameters using fiber optics
Authors: Junker B. H. , Wang D. I. C. , Hatton T. A. 
Published: December 2004

AbstractA method has been developed for measuring fermentation parameters such as dissolved oxygen, pH, and cell density that differs from traditional techniques that require electrodes and off‐line samples. Fluorescent indicators, each sensitive to a single variable, are dissolved directly into a fermentation broth. A fiber‐optic probe fluorimeter measures the fluorescence intensities that can then be correlated with parameter values. In addition, an integrated scatter scanning technique can be used to monitor cell density in situ. Results have been obtained using simulated baker's yeast broth and during actual baker's yeast fermentations.
Foam separation of microbial cells
Authors: Parthasarathy S. , Das T. R. , Kumar R. , Gopalakrishnan K. S. 
Published: December 2004

AbstractBatch foam separation has been employed to separate Saccharomyces carlsbergensis cells from their broth without the use of any external surface‐active agent. A model has been developed to predict the foamate cell concentration as well as the variation of cell concentration in the bulk liquid in the foam column as a function of time. The model assumes a linear equilibrium relation between the cell concentrations at the interface and the bulk. The foam has interface as well as interstitial liquid. The interface is assumed to be in equilibrium with the interstitial liquid, which in turn is assumed to have the same concentration as the bulk. The interfacial area is calculated by assuming the foam bubbles to be pentagonal dodecahedral in shape. The model has been found to explain the results of foam separation of cells quite well, particularly with respect to the effect of bubble size and aeration rate.
Recirculating bioreactor–separator system for simultaneous biotransformation and recovery of product: Immobilized L‐aspartate β‐decarboxylase reactor system
Authors: Takamatsu Satoru , Ryu Dewey D. Y. 
Published: December 2004

AbstractA new combined bioreactor‐separator system was designed and its operational feasibility demonstrated in order to develop a bioprocess that enables us to handle simultaneous biotransformation and recovery of product by crystallization. Enzymatic conversion of L‐aspartate to L‐alanine by L‐aspartate β‐decarboxylase from Pseudomonas dacunhae (ATCC 21192) was used as a model system for this study to demonstrate the principles involved in the bioprocess design. Immobilized cells of P. dacunhae containing the enzyme were fluidized in a tapered column type of bioreactor and a filter‐crystallizer combination was used as a separator unit in our experimental system.It was found that almost a theoretical yield was achieved, and the process control for both the bioreactor operation and separation was relatively easy. The Production systems, namely, the recirculating bioreactor separator combination system and the conventional batch reactor system, were analyzed and compared based on the results obtained form this study, and it was found that a significant cost reduction, by about 20%, can be achieved when the recirculating bioreactor–separator combination system was employed. Based on these findings, it is anticipated that the conceptual design of the bioreactor–separator combination system evaluated in this study has some potential for industrial application.
Design and mathematical description of differential contactors used in extractive fermentations
Authors: Roffler Stephen R. , Wilke Charles R. , Blanch Harvey W. 
Published: December 2004

AbstractThe performance of differential contactors for use in extractive fermentation is complicated by the effects of product formation in the contactor. When product formation is significant, approximate analytical solutions are presented for the performance of the contactor for two limiting cases: high and low substrate concentrations. When products are formed at a constant rate, there is a minimum raffinate solute concentration that can be obtained, in contrast to the behavior of a column in the absence of product formation. General equations describing the behavior of the system for product formation with backmixing in both phases are presented. The case of a stripping factor not equal to unity is considered.
Aerobic fungal cell immobilization in a dual hollow‐fiber bioreactor: Continuous production of a citric acid
Authors: Chung Bong Hyun , Chang Ho Nam 
Published: December 2004

AbstractAspergillus niger B60 was immobilized in a dual hollow‐fiber bioreactor (DHFBR) to produce citric acid continuously. The fungi proliferated well in the interstitial region formed by a parallel arrangement of three microporous polypropylene hollow fibers contained within a silicone tube. Long‐term operation with nitrogen‐enriched medium was not possible due to expansion of the silicone tubes by continual cell growth. The fungal growth could be controlled by supplying a nitrogen‐deficient medium at the production stage. With pure oxygen aeration and nitrogen‐deficient medium, volumetric productivity reached 1.62 g/L h at a residence time of 4.02 h, which corresponded to a 27‐fold increase over that of shake‐flask fermentation. When the residence time was increased to 20.1 h, citric acid at a concentration of 26 g/L was continuously produced, with a yield of 80‐90% and a volumetric productivity of 1.3 g/L h. This represents a significant improvement in final concentration, yield, and the volumetric productivity over the equivalent values of the corresponding batch fermentation, which were 18 g/L, 40%, and 0.06 g/L h, respectively.
A constant‐depth laboratory model film fermentor
Authors: Peters A. C. , Wimpenny J. W. T. 
Published: December 2004

AbstractA laboratory model constant‐depth film fermentor was developed. Film grew on the surface of polytetrafluoroethylene (PTFE) plugs and was limited to a predetermined depth by mechanically removing excess film. Six film‐forming organisms were isolated from river water and used to assess the operating characteristics of the fermentor. Film accumulation was logarithmic, and a steady state was maintained. Electron micrographs show early film development. The fermentor enables film to be grown on any substratum and allows discrete, reproducible, and representative samples to be taken.
Effects of charged groups in haptens on adsorption equilibrium of hapten antibody
Authors: Sada Eizo , Katoh Shigeo , Miyoshi Hirotoshi , Yamanaka Kuniko , Kondo Akihiko 
Published: December 2004

AbstractAntisera against charged (p‐azobenzoate and p‐azoben zenesulfonate) and uncharged (dinitrophenyl) haptenic groups were produced in rabbits, and the equilibrium characteristics of hapten‐antibody were measured by use of immunoadsorbents. The antibody to the uncharged hapten formed a stable binding with the hapten to the changes in ionic strength and pH. On the other hand, the antibodies to the charged haptens showed affinities sensitive to the changes in pH and ionic strength. Therefore, the effect of the pKa of ionizable haptens on the pH dependence of the hapten‐antibody binding was studied by comparing the interactions between a series of para‐substituted benzoic acids and the anti‐p‐azobenzoate antibody. The pH dependence of the interactions was strongly affected by the pKa of ionizable groups in haptens. Furthermore, the equilibrium characteristics of anti‐p‐aminobenzoyl dipeptides were compared. The characteristics of interactions were affected by the features of amino acid residues.
A new immobilization technique of whole cells and enzymes with colloidal silica and alginate
Authors: Fukushima Yaichi , Okamura Katsutoshi , Imai Kazutaka , Motai Hiroshi 
Published: December 2004

AbstractA mixed gel composed of colloidal silica and alginate (As gel) was prepared for the immobilization of enzymes or microorganisms. The physical strength of AS gel increased with the amount of colloidal silica. The ethanol production rate of Saccharomyces cerevisiae (IFO 0224) immobilized in AS gel was higher than in alginate gel (Al gel) in the early phase of growth. At a concentration of glucose of more than 10%, the ethanol production of immobilized yeast in AS gel was higher than in Al gel. Any difference was not recognized in the diffusion coefficient of glucose between AS and Al gels. The AS gel had an ability to retain proteins such as bovine serum albumin and γ‐globulin. The alkaline protease and β‐galactosidase in AS gel continued their function for a long time, but those immobilized in Al gel did not. Immobilized β‐galactosidase in AS gel had a higher thermal stability than in Al gel or free enzymes.
Membrane reactor coupled with electrophoresis for enzymatic production of aspartic acid
Authors: Lee C. K. , Hong J. 
Published: December 2004

AbstractAspartic acid production by aspartase reaction on ammonium fumarate was carried out in a membrane reactor coupled with electrophoresis. A pressurized, stirred vessel attached with an ultrafiltration membrane was used as a membrane reactor. An electric field was applied across the membrane to preferentially remove the product aspartate from the reactor into the permeate stream. The charged molecule, aspartate, is much smaller than the molecular‐weight cutoff of the membrane (104) so that the ions would move freely through pores of the membrane. The concentration of aspartate in the permeate stream is determined by the electromigration velocity of the ions and the permeation rate of solvent (water) through the membrane. The permeation rate of solvent could be controlled by the applied pressure, and the migration velocity of the ions could be controlled by the electric field strength applied. The equilibrium conversion of ammonium fumarate to the aspartate was 70%. In the presence of electric field, the aspartase activity was not disturbed. Also, it is shown that the aspartate concentration in the permeate stream was 20% higher than that in the reaction solution with the permeate flow rate of 0.7 mL/min. The steady‐state conversion was 60%. Instead of aspartate, aspartic acid can be recovered directly from the permeate stream by controlling the circulation of buffer electrolyte in the anode compartment.
Polyelectrolyte precipitation of proteins: I. The effect of reactor conditions
Authors: Fisher Rod R. , Glatz Charles E. 
Published: December 2004

AbstractLysozyme was recovered from egg white by continuous precipitation with polyacrylic acid (molecular weight of 4 × 106). Precipitator residence time and shear rate had significant effects on the size distribution of the precipitate, but no clear effects on the compositions. Precipitate mean size increased with higher shear, indicating growth phenomena predominating over breakage. Also, an enhancement of growth rate at small sizes was noted. The Camp number successfully characterized the interaction of shear rate and residence time on the particle size.
Adsorption of Trichoderma reesei cellulase on cellulose: Experimental data and their analysis by different equations
Authors: Steiner W. , Sattler W. , Esterbauer H. 
Published: December 2004

AbstractThe adsorption of cellulase from Trichoderma reesei MCG 77 on Avicel was measured at varying cellulase (2–8 g/L) and Avicel (10–200 g/L) concentrations at pH 4.8 and 50°C. Different mathematical equations were derived for the evaluation of the experimental data. The fraction of cellulase protein that can maximally be adsorbed is 0.96, and 1 g Avicel can bind maximally 0.092 g cellulase protein. The Michaelis constant for the adsorption equilibrium [cellulase] + [Avicel] ⇌ [cellulase Avicel] complex is between 2.0 and 2.3 · 10−5 mol/L. This value is based on the assumption that cellulase has an average molecular weight of 48.000. The apparent molecular weight of Avicel, i.e., that amount in grams that can bind 1 mol cellulase, is 520,000. Under maximum binding the enzyme covers on Avicel a surface of 42 m2/g, and the occupied volume is 0.186 cm3/g Avicel.
Effects of microcarrier concentration in animal cell culture
Authors: Croughan Matthew Shane , Hamel Jean‐François P. , Wang Daniel I. C. 
Published: December 2004

AbstractResults are presented which show how the microcarrier concentration affects the hydrodynamic environment in animal cell bioreactors. At low levels of agitation, no physical effects of microcarrier concentration were found. However, cell growth was strongly influenced by cell concentration. At high levels of agitation, a strong detrimental effect of microcarrier concentration was found. A new mechanism of hydrodynamic damage was identified which is second order in microcarrier concentration. The identification of this mechanism adds to the fundamental understanding of hydrodynamic phenomena in microcarrier bioreactors.
Shear stress induced stimulation of mammalian cell metabolism
Authors: Frangos J. A. , McIntire L. V. , Eskin S. G. 
Published: December 2004

AbstractA flow apparatus has been developed for the study of the metabolic response of anchorage‐dependent cells to a wide range of steady and pulsatile shear stresses under well‐controlled conditions. Human umbilical vein endothelial cell monolayers were subjected to steady shear stresses of up to 24 dynes/cm2, and the production of prostacyclin was determined. The onset of flow led to a burst in prostacyclin production which decayed to a long term steady state rate (SSR). The SSR of cells exposed to flow was greater than the basal release level, and increased linearly with increasing shear stress. This study demonstrates that shear stress in certain ranges may not be detrimental to mammalian cell metabolism. In fact, throughout the range of shear stresses studied, metabolite production is maximized by maximizing shear stress.
Enzymatic transesterifications of carbonates in water‐restricted environments
Authors: Abramowicz Daniel A. , Keese Charles R. 
Published: December 2004

AbstractWe investigated the ability of several hydrolases to catalyze reactions with an abiotic water‐insoluble substrate, carbonic acid diphenyl ester, also known as diphenyl carbonate (DPC). In single‐phase water/organic systems, turnover numbers (TN) of greater than 2 × 104 min−1have been achieved for the hydrolysis of DPC. The Km values for the hydrolytic reaction were measured to be 200μM and 330μM for Candida cylindracea lipase and Porcine liver esterase, respectively. In addition to hydrolysis, we observed transesterification of carbonates with a wide variety of alcohol and phenol species. Transesterifications of DPC with bifunctional alcohols resulted in the synthesis of polycarbonates. We investigated the stability and transesterification activity of these enzymes in several water‐restricted environments to limit competing hydrolysis reactions. We find that, with the removal of water, hydrolysis is reduced more than four orders of magnitude while transesterification is diminished only 10‐fold (turnover numbers of 600 min−1 in water‐miscible systems to 60 min−1 in water‐restricted environments with pure Candida lipase). Stability of the Candida lipase in these water‐restricted environments (half‐life of longer than 3 days) is much greater than in water/organic single phase systems (5 h in 20% methanol). In addition, the Candida lipase displayed enantiomeric selectivity in transesterifications of DPC with racemic 2‐butanol (greater than 80% ee).
Energy requirements for the size reduction of poplar and aspen wood
Authors: Holtzapple M. T. , Humphrey A. E. , Taylor J. D. 
Published: December 2004

AbstractThe energy requirements associated with conventional mechanical size reduction of poplar and aspen wood are compared to a new method of size reduction employing a wood planer. Although the planer requires about 2.3 times less energy to achieve the same size reduction as conventional methods, large‐scale equipment to implement this approach does not currently exist. Explosive depressurization was also compared to conventional mechanical size reduction. The conventional mechanical methods require roughly 70% more energy to achieve the same size reduction as explosive depressurization. Thus, explosive depressurization appears to be the preferred method and has the added benefit of altering the chemical structure of the wood to enhance the enzymatic hydrolysis of the cellulose fraction.
Biosynthesis of pullulan using immobilized Aureobasidium pullulans cells
Authors: Mulchandani Ashok , Luong John H. T. , LeDuy Anh 
Published: December 2004

AbstractImmobilization of Aureobasidium pullulans by adsorption on solid supports and entrapment in open pore polyurethane foam were attempted. By adsorption, the highest cell loading of 0.012–0.018 g dry wt/cm2 support was obtained in pH 2.0 medium. Under this acidic condition, the net surface charges (zeta potentials) of both the cells and supports were close to zero and no pullulan was synthesized. Cationic coatings of Cytodex and polyethylenimine were not efficient in enhancing the binding strength between the cells and the supports. Surface immobilized cells and polyurethane foam entrapped cells exhibited a similar fermentation characteristics resulting in ca. 18 g/L pullulan and ca. 5 g/L leaked cells. However, cells entrapped in the polyurethane foam were more shear resistant. The immobilized cells thus could be repeatedly used for pullulan biosynthesis.
Immobilized enzymes in reverse micelles: Studies with gel‐entrapped trypsin and α‐chymotrypsin in AOT reverse micelles
Authors: Fadnavis Nitin W. , Luisi Pier Luigi 
Published: December 2004

AbstractTrypsin and α‐chymotrypsin were immobilized by gelentrapment in polyacrylamide cross‐linked with N,N1‐methylenebisacrylamide. The immobilized enzymes are catalytically efficient in suspensions of reverse micelles formed in isooctane by bis(2‐ethylhexyl) sodium sulfosuccinate (AOT) and water. Both entrapped enzymes are stable in reverse micellar suspension at room temperature and pH 8.2 for 3 days and lose 30‐40% activity after 1 week. The enzymes obey Michaelis‐Menten kinetics in the investigated concentration range with Km values higher than those in solution. Activity of the enzymes is independent of the water content of the micellar solution. No shift in pH optimum was observed for immobilized trypsin activity toward Nα‐benzoyl‐L‐arginine ethyl ester. The utility of the procedure, which combines the advantage of enzyme immobilization and enzymology in reverse micelles, is illustrated by an example of peptide synthesis. In particular, peptide synthesis (e. g., ZAlaPheLeuNH2) using water‐insoluble substrate has been performed with gelentrapped α‐chymotrypsin in reverse micellar suspension with the advantage of efficient enzyme recycling.
Disruption of native and recombinant Escherichia coli in a high‐pressure homogenizer
Authors: Sauer Thomas , Robinson Campbell W. , Glick Bernard R. 
Published: December 2004

AbstractThe disruption of native and recombinant strains of Escherichia coli was studied using a high‐pressure homogenizer (Microfluidizer). The cells were grown in both batch and continuous fermentations. Cell suspensions ranging from 4 to 175 g dry wt/L were investigated at disruption pressures ranging from 30–95 MPa and at up to five passes. For both types of cells, the fraction of cells disrupted was dependent on the growth rate and concentration of the cells, the disruption pressure, and the number of passes through the disrupter. A model is presented that correlates the fractional disruption with these operating variables. The recombinant strain disrupted more readily than the native strain; 95 to 98% disruption of the former was achieved in two to three passes at a pressure of 95 MPa.
Dynamic pressure method for kla measurement in large‐scale bioreactors
Authors: Linek V. , Beneš P. , Vacek V. 
Published: December 2004

AbstractA dynamic method is proposed for kla measurement in aerated and agitated reactors, in which a change in the total pressure in the reactor by approximately 20% leads to a simultaneous change in the oxygen concentration in all the bubbles in the dispersion. This procedure suppresses the influence of nonideal mixing of the gas phase on the kla value. Other dynamic methods so far used do not possess this advantage. They are based on a step change in oxygen concentration in the entering gas, where the interfacial nitrogen transport and the finite rate of the concentration change propagation into the individual bubbles in the dispersion can cause an error in the reported kla values of more than hundreds of percent. The reliability of the pressure method is tested by comparison both with the standard dynamic method, in which pure oxygen is absorbed in a liquid from which all other gas components were previously removed, and with the steady‐state sulphite method. The signal of the oxygen probe used in the experiments must be independent of the pressure. A test for this in dependence is described. The pressure method is also suitable for large‐scale reactors since the necessary pressure changes are sufficiently small and, morever, air can be used.
A new method for the adaptive determination of optimum pH and temperature
Authors: Harmon Jeff. L , Lyberatos Gerasimos , Svoronos Spyros A. 
Published: December 2004

AbstractAn adaptive control algorithm for the on‐line determination of optimal temperature or pH for biomass production in a continuous fermentor is presented. The algorithm requires no prior information and uses a dynamic Hammerstein model to identify parameters and to estimate an optimal steady‐state control value. A check of the estimated performance measure second derivative is included to ensure that the target extremum is an optimum. The process is driven towards this optimum with a variable step size that depends on the quality of the on‐line identified model. Numerical simulations are performed on a dynamic chemostat model that incorporates a metabolic time delay. The algorithm successfully finds the optimum temperature or pH values and maintains the reactor at the optimum steady state.
Formal modeling of approximate relations in biochemical systems
Authors: Mavrovouniotis Michael L. , Stephanopoulos George , Stephanopoulos Gregory 
Published: December 2004

AbstractAiming to satisfy the need for the formalization of semiquantitative reasoning in the analysis of biochemical systems, the O[M] formalism for reasoning with orders of magnitude and approximate relations has been developed. It is based on seven primitive relations among quantities and compound relations which are formed as implicit disjunctions of primitives. O[M] can perform inferences by using formal approximate relations, algebraic equations, inequalities, if–then rules, assumptions, and goals. The applications discussed include Michaelis–Menten kinetics, different modes of inhibition of an enzymatic reaction, analysis of fluxes in biochemical networks, and identification of rate‐limiting steps of biochemical pathways. In these applications, O[M] provides a medium for acquisition and formalization of previously informal concepts, analysis of systems at the order‐of‐magnitude level of detail, and automation of commonsense reasoning.