bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution of heparinase covalently immobilized to agarose: Experimental and theoretical studies
Authors: Bernstein Howard , Yang Victor C. , Langer Robert 
Published: December 2004

AbstractAn immobilized enzyme reactor has been developed to remove heparin, the anticoagulant that is required in all extracorporeal devices for patients undergoing open‐heart surgery or kidney dialysis. The device uses the enzyme heparinase (EC 4.2.2.7), which is covalently linked to agarose with cyanogen bromide. A critical parameter in the development of a model for the degradation of heparin catalyzed by immobilized heparinase is the radial concentration profile of the enzyme within the agarose matrix. Experimental determinations of bound enzyme con centrations have been conducted previously for several enzyme systems using radioactive or fluorescent labels. For the development of the heparinase reactor it is necessary to use catalytically but not electrophoretically pure enzyme, and thus it is not possible to use the labeling techniques. To obtain information about the bound enzyme distribution, an experimental study of the intrinsic binding kinetics of heparinase to cyanogen bromide‐activated agarose was conducted. The binding reaction was studied as a function of both the concentration of heparinase and the gel‐reactive group. At conditions of functional group excess, the binding kinetics were pseudo first order in heparinase concentration with a rate constant equal to 0.12 Ccn (h−1), where Ccn is the gel‐reactive group concentration. The reactive group concentration remained constant within the 2–4‐h experiments. Competitive binding between heparinase and the protein contaminants was unimportant. A model was formulated for the immobilization procedure based on the diffusion of heparinase within the porous network and the binding kinetics as determined above. The model predicted the immobilization of heparinase to be kinetically controlled and the enzyme to distribute uniformly within the agarose matrix. These experimental techniques could be applied to predict the immobilized enzyme distribution for different enzyme systems that are not electrophoretically pure.
Combined submerged and solid substrate fermentation for the bioconversion of lignocellulose
Authors: Viesturs U. E. , Strikauska S. V. , Leite M. P. , Berzins A. J. , Tengerdy Robert P. 
Published: December 2004

AbstractA novel two‐stage bioreactor has been designed for a combined submerged (SF) and solid substrate fermentation (SSF) of wheat straw. The straw was pretreated with steam, and cellulases from the culture fluid of Trichoderma reesei were adsorbed on it for increased bioconvertibility. SSF was conducted in the top part of the bioreactor by inoculating the straw with a 36‐h mycelial culture of T. reesei, or Coriolus versicolor. In the bottom part of the fermenter, Endomycopsis fibuliger was grown in SF. The SF liquor was recirculated through the SSF stage at 24 h intervals to remove glucose and other metabolites that may inhibit growth, and to maintain optimum moisture level and temperature. The removed glucose and other metabolites provided nutrients for the yeast in the SF stage. The combined fermentation resulted in overall higher biomass yield, increased bioconversion, increased cellulase production, and increased digestibility compared with single SSF or SF.
Methanogenesis from volatile fatty acids in downflow stationary fixed‐film reactor
Authors: Bhadra Amit , Scharer Jeno M. , Moo‐Young Murray 
Published: December 2004

AbstractMethanogenesis was studied in downflow stationary fixed‐film bioreactors. The support materials in this study included ceramic Raschig rings, hardwood chips, and sized charcoal. The performances of these support materials have been compared using both synthetic acid mixture and acid products obtained from paper mill sludge. Woodchips appeared to be the most promising support material: The maximum methane productivity of 3.56 L/L day at a nominal retention time of 0.78 day was obtained using initial total acid concentrations of 9.125 g/L. Higher productivity was achieved at the cost of efficiency of the process in terms of conversion of acids. From nitrogen balances, it was deduced that ammonia supplemented methane generation by supplying hydrogen for there duction of carbon dioxide.An ionic balance was developed to ascertain the relationship between the composition and the pH of the liquid and the mole fraction of carbon dioxide in the gas phase. From these ionic balance equations, it was possible to predict the gas phase composition at various retention times. The maximum error between the computed and the experimental values was less than 13%.
Kinetic expression for maltose production from soluble starch by simultaneous use of β‐amylase and debranching enzymes
Authors: Shiraishi Fumihide , Kawakami Koei , Yuasa Akio , Kojima Tsuyoshi , Kusunoki Koichiro 
Published: December 2004

AbstractThe kinetics of the hydrolysis of soluble starch by simultaneous use of β‐amylase and either isoamylase or pullulanse was studied experimentally for a wide range of subtrate and enzyme concentrations. A kinetic expression was constituted for maltose production by β‐armylase, which was stimulated by an increase in linear linkage portions due to the debranching enzyme on amylopectin molecules. As a result, calculations by the kinetic expression agreed with time course data under various conditions.
Continuous cellulase production by immobilized Sporotrichum cellulophilum and continuous saccharification of bagasse
Authors: Tamada Masao , Kasai Noboru , Kaetsu Isao 
Published: December 2004

AbstractImmobilized Sporotrichum cellulophilum with nonwoven materials was cultured continuously by a rotating‐disk fermentor to supply cellulase into the saccharification system. The filter paper activity (5.0) was retained after 696 h under conditions of 250 rpm stirring and 0.014 h−1 dilution rate. The product of the culture was supplied continuously to the saccharification reactor and used for the saccharification of bagasse. A glucose solution of ca. 0.9% was obtained continuously from 5% bagasse slurry during 610 h saccharification by this method.
Mathematical modelization of a packed‐bed reactor performance with immobilized yeast for ethanol fermentation
Authors: Gòdia F. , Casas C. , Solà Ç. 
Published: December 2004

AbstractThe performance of a continuous vertical packed‐bed reactor with yeast immobilized in carrageenan gel beads is reported. The study focuses on the mathematical modelling of the steady‐state fermentor behavior by means of a tanks‐in‐series model which includes the intrinsic kinetic model and the external mass transfer and internal diffusion‐reaction conditions in the beads.
A novel technique for measuring solute diffusivities in entrapment matrices used in immobilization
Authors: Merchant F. J. A. , Margaritis A. , Wallace J. B. , Vardanis A. 
Published: December 2004

AbstractA novel technique has been developed for measuring effective solute diffusivities in entrapment matrices used for cell immobilization. In this technique radiotracers were used to measure effective diffusivities and equilibrium partition coefficients of the solute between the liquid and solid matrix. Ca‐alginate was used in this study, because it is one of the most commonly employed matrices for the immobilization of microbial, plant and mammalian cells. The experimental apparatus consisted of a single spherical Ca‐alginate bead which was attached to a rotating rod and immersed in water containing C14‐glucose. The rotational speed of the spherical bead was controlled and resulted in excellent mixing, and negligible external film mass transfer resistance, which allowed the measurement of true effective solute diffusivity within the solid matrix. The rates of C14‐glucose diffusion within the Ca‐alginate sphere were measured using a scintillation spectrometer. A mathematical model of unsteady‐state diffusion in a sphere was used with appropriate boundary conditions, and the effective diffusivity of glucose was found from the best fit of the experimental data using a computer regression analysis method. Using 2% (w/v) Ca‐alginate beads in this new radiotracer technique the effective diffusivity and partition coefficient of glucose were found to be 6.62 × 10−10 m2/s and 0.98, respectively. The accuracy, advantages, and simplicity of this new method for diffusivity measurements are also compared to other existing methods.
Microheterogeneity of enzymes and deactivation
Authors: Sadana Ajit , Malhotra Arun 
Published: December 2004

AbstractThe influence of microheterogeneity on enzyme inactivation kinetics is presented. Examples of different enzymes are given where microheterogeneity has been detected by different techniques. The different statistical models are presented which include the influence of microheterogeneity on enzyme inactivation kinetics and stability. As the microheterogeneity of the enzyme increases, there is a sharper decline in the normalized activity during the initial stages of the deactivation but a greater stability and activity, compared to similar homogeneous enzyme, as the deactivation proceeds. Microheterogeneity makes the deactivation reaction have a higher apparent order of reaction. The implications of microheterogeneity on enzyme inactivations are high lighted by different examples. The analysis provides fresh physical insights into the chemistry, subpopulations, structure, and function of enzymes.
Thermochemical pretreatment of lignocellulose to enhance methane fermentation: I. Monosaccharide and furfurals hydrothermal decomposition and product formation rates
Authors: Baugh Kent D. , McCarty Perry L. 
Published: December 2004

AbstractOver a pH range 1–4 and temperatures from 170 to 230°C, the decomposition rates of xylose, gaiactose, mannose, glucose, 2‐furfural, and 5‐hydroxymethyl‐2‐furfural (5‐HMF) were pseudo first order. The effect of temperature and pH on the pseudo first‐order decomposition rate constants was modeled using the Arrhenius equation and acid‐base catalysis, respectively. Decomposition rates of the monosaccharides were minimum at a pH 2–2.5. Above pH 2.5, the monosaccharide decomposition was base catalyzed, with acid catalysis occurring at a pH of less than 2 for glucose. The furfurals were subject to acid catalysis at below ca. pH 3.5. The hydrothermal conversion of glucose to its decomposition products during thermochemical Pretreatment can be modeled as a combination of series and parallel reactions. The formation rates of identified soluble products from glucose decomposition, 5‐HMF and levulinic acid, were also functions of temperature and pH. The rate of 5‐HMF formation relative to glucose decomposition decreased as the pH increased from 2.0 to 4.0, with levulinic acid formation only detected when the pH was 2.5 or less. For glucose decomposition, humic solids accounted for ca. 20% of the decomposition products.
Selection of thermotolerant yeast strains for simultaneous saccharification and fermentation of cellulose
Authors: Szczodrak J. , Targoński Z. 
Published: December 2004

AbstractA total of 58 yeast strains from 12 genera were assayed for their ability to grow and ferment carbohydrates in standard Durham tube test at 40, 43, and 46°C. Based on the kinetic parameters for glucose fermentation in shaken flask cultures, the strain Fabospora fragilis CCY51‐1‐1 was chosen for further studies. It reached about 56.0 and 35.0 g ethanol/L from ∼140 g glucose/L at 43 and 46°C in less than 48 h, respectively. Trichoderma reesei cellulase preparation (400 FPU/L) had not distinct effect on the ethanol yield and biomass production by the selected strain in the first 12 h fermentation at 46°C. Later a negligible decrease in both yields was observed. It was found that Fabospora fragilis did not grow or produce ethanol at 46°C as tho initial ethanol concentration overcame 40 g/L.
Hydrolysis of beef tallow by lipase from Pseudomonas sp.
Authors: Kosugi Yoshitsugu , Suzuki Hideo , Funada Tadashi 
Published: December 2004

AbstractThe lipase produced by Pseudomonas fluorescens biotype I was selected for hydrolyzing beef tallow at 50–70°C to more than 90% of reaction ratio. Using an amount of lipase sufficient to reach equilibrium, the final reaction ratio was decreased with increasing temperature and the apparent enthalpy of beef tallow hydrolysis obtained by the final reaction ratio was −1.93 × 104cal/mol, and the final reaction ratio also decreased with increasing substrate concentration. The rising time, which is the reaction time up to one‐half of the final reaction ratio, decreased remarkably with increasing temperature, and was closely related to the value of the maximum velocity by the Michaelis constant of this lipase. The final reaction ratio increased with increasing lipase amount up to equilibrium. Increasing the lipase above the amount required to reach equilibrium caused a decrease in the rising time. The feasibility of using parameters obtained by a hyperbolic simulation of the progress curve is discussed.
High‐pressure—temperature bioreactor for studying pressure—temperature relationships in bacterial growth and productivity
Authors: Miller Jay F. , Almond Edward L. , Shah Nilesh N. , Ludlow Jan M. , Zollweg John A. , Streett William B. , Zinder Stephen H. , Clark Douglas S. 
Published: December 2004

AbstractThermophilic organisms offer many potential advantages for biotechnological processes; however, realization of the promise of thermophiles will require extensive research on bacterial thermophily and high‐temperature cultivation systems. This article describes a novel bioreactor suitable for precise studies of microbial growth and productivity at temperatures up to 260°C and pressures up to 350 bar. The apparatus is versatile and corrosion resistant, and enables direct sampling of both liquids and gases from a transparent culture vessel without altering the reaction conditions. Gas recirculation through the culture can be controlled through the action of a magnetically driven pump. Initial studies in this bioreactor of Methanococcus jannaschii, an extremely thermophilic methanogen isolated from a deep‐sea hydrothermal vent, revealed that increasing the pressure from 7.8 to 100 bar accelerated the production of methane and cellular protein by this archaebacterium at 90°C, and raised the maximum temperature allowing growth from 90 to 92°C. Further increases in pressure had little effect on the growth rate at 90°C.
A continuous affinity ultrafiltration process for trypsin purification
Authors: Luong J. H. T. , Male K. B. , Nguyen A. L. 
Published: December 2004

AbstractA continuous process has been devised and tested for purification of a crude trypsin preparation from pig pancreas. The development was based on the principles of affinity chromatography and Ultrafiltration. Trypsin was selectively attracted by a water‐soluble high molecular weight (>100,000) polymer, bearing a potent and specific trypsin inhibitor, m‐aminobenzamidine. The trypsin‐macroligand complex was then retained by using an appropriate Ultrafiltration membrane, while impurities could pass through. The bound trypsin was eluted by either arginine or benzamidine. The process also featured provision for recirculation of the eluant as well as the macroligand. It was demonstrated that this purification process could purify trypsin from the crude preparation with a yield of 77%, contaminated with only 3% of impurities. For the first time, a serious attempt has been made toward continuous purification of enzymes by the affinity Ultrafiltration technique. Besides a substantial increase in productivity, the affinity polymer could be easily reconditioned and expected to possess a long operative life. Such characteristics undoubtedly will play an important role in reducing the cost of trypsin purification.
Enzyme hydrolysis of plasma proteins in a CSTR ultrafiltration reactor: Performances and modeling
Authors: Bressollier Ph. , Petit J. M. , Julien R. 
Published: December 2004

AbstractBy investigating the effects of four operating variables—volume (V), Ultrafiltration flux (J), enzyme concentration (E), and substrate concentration (S)—on capacity (K) and conversion rate (ε) of a hollow fiber CSTR, the performances of the CSTR and the kinetic constants of the reaction were determined. A model which takes into account the course of fractional conversion (X) according to the modified space–time parameter, τ (integrated form of V, J, S, and E), was devised by employing the relationship to integrate the equation for the reaction rate of the CSTR and the expression of the modified space time. Correlation of this model and the experimentally obtained results demonstrates that the characteristics for an ultrafiltration membrane reactor for enzymatic hydrolysis by alcalase of plasma proteins are close to those of an ideal CSTR. Optimal scaling up, however, remains dependent on the compromise which may be obtained between capacity and the conversion rate.
On the optimal control of fed‐batch reactors with substrate‐inhibited kinetics
Authors: Cazzador Lorenzo 
Published: December 2004

AbstractThe optimal feed rate profiles, for fed‐batch fermentation that maximizes the biomass production and accounts for time, are analyzed. The solution can be found only if the final arc of the optimal control is a batch arc, since in this case the final concentrations of substrate and biomass can be determined by ulterior conditions on the mass balance and on the final growth rate of biomass and thus it is possible to solve the resulting time optimal problem by using Green's theorem. This evidences the “turnpike property” of the solution, which tries to spend the maximum time on or at least near the singular arc along which the substrate concentration is maintained constant. The optimality of the final batch arc is related to the time operational cost in the performance index. The sequence of the control depends on the initial conditions for which six different regions, with the respective patterns, have been identified, in case the performance index allows the control sequence to have a final batch.
Improved performance in viscous mycelial fermentations by agitator retrofitting
Authors: Buckland B. C. , Gbewonyo K. , Dimasi D. , Hunt G. , Westerfield G. , Nienow A. W. 
Published: December 2004

AbstractFor viscous mycelial fermentations it was demonstrated at the pilot‐plant scale that the replacement of standard radial flow Rushton turbines with larger diameter axial‐flow Prochem hydrofoil impellers significantly improved oxygen transfer efficiency. It was also determined that the Streptomyces broth under evaluation is highly shear thinning. Separate experiments using a Norcardia broth with similar Theological properties demonstrated that the oxygen transfer coefficient, KLa, can be greatly increased by use of water additions to reduce broth viscosity. These observations are consistent with the hypothesis that the improvement in oxygen transfer by changing agitator types is primarily due to an improvement in bulk mixing. A model is presented, based on the concepts of Bajpai and Reuss, which explains this improvement in performance in terms of enlargement of the well mixed micromixer region for viscous mycelial broths.
Stability and expression of a plasmid‐containing killer toxin cDNA in batch and chemostat cultures of saccharomyces cerevisiae
Authors: Lee Fang‐Jen S. , Hassan H. M. 
Published: December 2004

AbstractA chimeric plasmid (pYT760‐ADH1) containing the yeast killer toxin–immunity cDNA was transformed into a leucine–histidine mutant (AH22) and into four industrial toxin‐sensitive yeasts. The chimeric plasmid was very stable and expressed toxin production (89.5 ± 4.8% killer cells) in two of the transformed yeasts that contained the 2μ plasmid, but was lost within 10 generations from two other transformed pickle yeasts that did not contain the 2μ plasmid. It suggested that plasmid stability was dependent on the presence of the 2μ plasmid which is naturally present in some yeasts. The plasmid was extremely stable (100% killer cells) and expressed more toxin in the mutant strain AH22. The effects of dilution rate, D(h−1) on plasmid stability and toxin expression were studied in transformed AH22 (AH22/T3) and Montrachet 522 (522/T1) wine yeast grown in glucose‐limited chemostat cultures. The results show that killer toxin production by AH22/T3 cells increased as a function of D(h−1) and that plasmid stability reached 100% at D ≥ 0.09 ± 0.01 h−1. However, with Montrachet 522/T1 transformed cells, 100% plasmid stability was seen at D ≥ 0.18 ± 0.02. h−1. We also challenged the AH22/T3 in chemostat culture (D = 0.25 h−1) with an equal number of untransformed cells (AH22). Transformed cells dominated the population (100%) within 8–10 h of growth, a time equivalent to two mean residence time.
Bioreactor considerations for secondary metabolite production from plant cell tissue culture: Indole alkaloids from Catharanthus roseus
Authors: Payne Gregory F. , Payne Nadine N. , Shuler Michael L. 
Published: December 2004

AbstractBatch shake flask studies with Catharanthus roseus demonstrated that alkaloid production commenced only after growth had slowed or ceased. To obtain high alkaloid productivities for extended periods, a hormone‐free production medium was used. To develop a readily scalable process, both immobilized and suspended cell systems were studied. In the immobilized cell systems, growth, glucose utilization, and alkaloid production were suppressed; for the case of membrane entrapped cells this suppression was observed to be reversible. Based on the oxygen requirements of the cells, and the oxygen transfer capabilities of a pneumatically agitated bubble column, conditions were established that allowed the growth and production dynamics observed in shake flasks to be reproduced in the air sparged column reactor. The requirement for the aseptic exchange of growth for production medium was satisfied by using a coarse cotton filter and coupling filtration to aeration. With this filtration system, media can be rapidly and completely exchanged and the filter can be quickly and effectively backwashed. By coupling filtration to aeration, a two‐stage batch operation can be employed while requiring only a single bioreactor. Studies with this system demonstrated its capabilities for alkaloid production.
Performance of membrane fixed biocatalyst reactors. I: Membrane reactor systems and modelling
Authors: Prenosil J. E. , Hediger T. 
Published: December 2004

AbstractEnzymatic membrane reactors are discussed according to the state of biocatalyst and driving force of reaction. Particular attention is given to the Capillary Membrane Fixed Enzyme Reactor (CAMFER) for its favorable characteristics. It is shown that, for a practical range of operation conditions, both kinetic and mass transfer effects must be considered simultaneously. Three modes of operation were investigated in detail using enzymatic lactose hydrolysis as a model reaction: Diffusional reactor, Recycle reactor, and Backflush reactor. In the comparison, superior performance of the CAMFER in diffusional mode was clearly demonstrated.