bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of the kinetics of reactions catalyzed by enzymes attached to membranes
Authors: Kobayashi Takeshi , Laidler Keith J. 
Published: December 2004

AbstractA theoretical treatment has been worked out for the kinetics of solid‐supported enzyme systems, with diffusive and electrostatic effects taken into account. A utilization factor, defined as the ratio of the actual reaction rate to the rate of substrate consumption in the outer solution, is defined, and equations to evaluate the utilization factor are given for five kinetic conditions: (a) Michaelis‐Menten behavior, (b) substrate inhibition, (c) product inhibition (competitive), (d) product inhibition (noncompetitive), and (e) product inhibition (anticompetitive). When the solid‐supported enzymes obey a Michaelis‐Menten relationship, an equation for the apparent Michaelis constant is given and a criterion for insignificant diffusion effects is shown. A substrate‐inhibited enzyme reaction may display multiple steady‐state behavior, and a criterion for uniqueness is presented. In the case of product‐inhibited enzyme reactions, the utilization factor is always less than that which corresponds to a Michaelis‐Menten relationship. Equations to evaluate the apparent Michaelis and inhibition constants are given.
Immobilization of enzymes on magnetic particles
Authors: Van Leemputten E. , Horisberger M. 
Published: December 2004

AbstractTrypsin (EC 3.4.4.4) was immobilized in low yield on aminoalkylsilylated magnetite (Fe3O4). Better results were obtained when trypsin was immobilized by crosslinking with glutaraldehyde on magnetite. The preparation contained 36 mg protein/g magnetite and the enzyme retained 46% and 11% of esterase and proteolytic activity. Immobilized trypsin was more heat stable than trypsin. Invertase (β‐D‐fructofuranoside fructohydrolase, EC 3.2.1.26) was cross‐linked on magnetite with glutaraldehyde in low yield due to the inactivation of the enzyme. However in the presence of 1% sucrose, the total activity recovered was 79% of the initial activity and the preparation contained 4.4 mg/g of active invertase. Immobilized invertase was less active than invertase when acting on oligosaccharides of the raffinose family. The immobilized enzymes could be easily recovered, from solutions or suspensions, magnetically.
Reduction and separation of nitrate and nitrite by liquid membrane‐encapsulated enzymes
Authors: Mohan Raam R. , Li Norman N. 
Published: December 2004

AbstractPurified enzymes encapsulated in liquid surfactant membranes have been shown to retain their catalytic activity. In general, previous work on encapsulation has been confined to single enzymes. The system has now been extended to encapsulate a bacterial cell‐free homogenate. Liquid membrane‐encapsulated bacterial cell‐free homogenate reduces effectively NO3− to NO2− and other nitrogen compounds of lower oxidation state. This technique of removing nitrates and nitrites may have application in waste‐water treatment. Also, it has been shown that encapsulated cell‐free homogenate does not leak and there is no absorption of the substrate onto the liquid surfactant membrane surfaces. The reduction in the reaction rates is discussed in terms of solubility of the substrate and the rate of permeation of the substrates through the liquid surfactant membrane.
Preparation of an immobilized two‐enzyme system, β‐amylase‐pullulanase, to an acrylic copolymer for the conversion of starch to maltose. I. Preparation and stability of immobilized β‐amylase
Authors: Mårtensson Kaj 
Published: December 2004

Abstractβ‐Amylase (EC 3.2.1.2), obtained from barley, was chemically attached to a crosslinked copolymer of acrylamide‐acrylic acid using a water‐soluble carbodiimide. The derivative showed 23% β‐amylase activity in relation to that of free enzyme with a coupling yield of 40% based on the amount of added β‐amylase. In order to find optimal coupling conditions, the effect of pH and different carbodiimide concentrations was investigated. The enzymic activity associated with different β‐amylase concentrations was further outlined. A slightly increased operational stability for the enzyme upon immobilization was observed. Markedly improved operational stability has been obtained by coupling in the presence of reduced glutathione of bovine serum albumin.
Preparation of an immobilized two‐enzyme system, β‐amylase‐pullulanase, to an acrylic copolymer for the conversion of starch to maltose. II. Cocoupling of the enzymes and use in a packed bed column
Authors: Mårtensson Kaj 
Published: December 2004

Abstractβ‐Amylase (EC 3.2.1.2) and pullulanase (EC 3.2.1.9) have been covalently bound in a two‐enzyme system to a crosslinked copolymer of acrylarmide‐acrylic acid by using a water‐soluble carbodiimide. The coupling yields based on the amounts of added β‐amylase and pullulanase were 40% and 38%, respectively, with residual enzymic activities of 22% and 32% of those of free enzymes. A markedly increased operational stability was observed for the immobilized two‐enzyme system compared to the free enzymes in solution. In order to find optimal operational conditions the influence of different pH values and temperatures on the conversion process was investigated. The action of the immobilized β‐amylase‐pullulanase derivative on partially hydrolyzed starch (DE 3.4–10.7) in a packed bed column was studied. Analysis of the product was performed using gas‐liquid chromatography.
Continuous hydrocarbon fermentation with colloidal emulsion feed. A kinetic model for two‐liquid phase culture
Authors: Yoshida Fumitake , Yamane Tsuneo 
Published: December 2004

AbstractCandida tropicalis was cultured in a chemostat‐type fermentor with n‐hexadecane, dispersed in water as submicron droplets, as the only carbon substrate. The emulsion as well as the aqueous medium were fed continuously into the fermentor. A Monod‐type equation can correlate the specific group rate in the continuous fermentor with the concentration of submicron droplets. The same equation can also be fitted to the data for the conventional‐type batch culture in the same fermentor in which an oil phase as well as an aqueous phase existed, if the hydrocarbon concentration in the aqueous phase excluding oil drops is employed as the substrate concentration. This demonstrates that Candida tropicalis takes up only submicron droplets of n‐hexadecane as the carbon substrate.
Preparation of immobilized lactase. Continued studies on the enzymatic hydrolysis of lactose
Authors: Weetall H. H. , Havewala N. B. , Pitcher W. H. , Detar C. C. , Vann W. P. , Yaverbaum S. 
Published: December 2004

AbstractA soluble fungal lactase (lactase‐W) of greater activity that the previously available fungal lactase (lactase‐M) has been covalently coupled to ZrO2‐coated porous glass particles and 1 mm diameter porous TiO2 particles. The immobilized lactase‐W appears to give results similar to the lactase‐M except for the operational half‐life. At 30°C the half‐life of the lactase‐M appears to exceed that of the lactase‐W by approximately 100 days under operational conditions.
Kinetics of formation of humic substances in activated sludge systems and their effect on flocculation
Authors: DeWalle F. B. , Chian E. S. K 
Published: December 2004

AbstractHumic substances were isolated during batch aeration studies with activated sludge and a complex waste source, by using concentration and separation techniques that employ reverse osmosis, ultrafitration, and gel permeation chromatography. The study suggests that the formation of high molecular weight humic substances may occur after the removal of the readily available carbon source. The amount of refractory material finally present in the solution will depend on its adsorptive properties toward bacterial cells. The adsorptive characteristics may be determined by the magnitude of the carbohydrate fraction present in the humic substances. If the carbohydrate content decreases, adsorption onto the cells may decrease resulting in an impairment of both the floe formation and settleability of the sludge floes. Decreased adsorption will result in a higher total organic carbon content and an increase in color bearing materials in the effluent.
Temperature effects on anaerobic fermentation of domestic refuse
Authors: Pfeffer John T. 
Published: December 2004

AbstractAnaerobic fermentation of organic solid waste can provide a significant source of fuel gas (methane). Application of this process requires a better understanding of the kinetics of the biological system. The literature is replete with kinetic studies of this process as applied to waste solids from water pollution control systems. Much of this work has been conducted in the mesophilic temperature range. Increased temperatures yield higher reaction rates that will improve the economics of the process. The rate limiting step in the fermentation of refuse is the hydrolysis of the complex organic solids, in particular cellulose. Cellulose is a major component of the refuse. A laboratory study employing domestic refuse has shown the effect of temperature on the rate of methane fermentation. The optimum mesophilic temperature was found to be 42°C, while the optimum thermophilic temperature was at least 60°C. No data was obtained beyond the 60°C temperature. Reaction rate constants are presented for anaerobic fermentation of domestic refuse. Because of the characteristics of the substrate it−was not possible to obtain the necessary measurements for evaluation of constants in the Monod model. An overall system constant was developed.
External and internal diffusion in heterogeneous enzymes systems
Authors: Horvath Csaba , Engasser Jean‐Marc 
Published: December 2004

AbstractThe intrusion of diffusion in heterogeneous enzyme reactions, which follow. Michaelis‐Menten kinetics, is quantitatively characterized by dimensionless parameters that are independent of the substrate concentration. The effects of these parameters on the overall rate of reaction is illustrated on plots commonly employed in enzyme kinetics. The departure from Michaelis‐Menten kinetics due to diffusion limitations can be best assessed by using Hofstee plots which are also suitable to distinguish between internal and external transport effects. A graphical method is described for the evaluation of the reaction rate as a function of the surface concentration of the substrate from measured data.
Maximal exponential growth rate and yield of E. coli obtainable in a bench‐scale fermentor
Authors: Bauer S. , Shiloach J. 
Published: December 2004

AbstractOxygen supply is one of the main factors which influences aerobic cell growth in a fermentor. Maximal rates at which E. coli can grow on glucose as carbon source under various limiting oxygen‐supply conditions were determined in a bench‐scale fermentor. Culture conditions are described which gave yields of about 38 g dry cells per liter medium.
Gel entrapped enzymes: Kinetic studies of immobilized β‐galactosidase
Authors: Hinberg I. , Korus R. , O'Driscoll K. F. 
Published: December 2004

Abstractβ‐galactosidase from E. coli (β‐D‐galactose galactohydrolase, EC 3.2.1.23) has been entrapped in a crosslinked 2‐hydroxyethyl methacrylate gel with a 35% retention of activity. The kinetic behavior of the gel‐entrapped enzyme has been studied in a recirculation reactor system, the substrate being o‐nitrophenyl‐βhyphen;D‐ galactopyranoside. Kinetic constants were determined for particle sizes ranging from 69 to 231 μm in diameter and compared to those of the free enzyme. External diffusion effects were eliminated by operating at high recirculation flow rates. A fourfold increase in Km(app) was observed for the 231 μm particles, consistent with existing theoretical treatments for internal diffusion effects.An Arrhenius plot of rate data showed significant curvature at higher temperatures, which was attributed to the effects of internal diffusion. The pH–activity profile of the gel‐entrapped enzyme was bell‐shaped at high substrate concentration and, in contrast to the free enzyme, could be fitted to the titration curve of two ionizable groups, a basic group having a pK of 8.6. The gel‐entrapped enzyme had a higher pH optimum and retained a larger percentage of its maximal activity at alkaline pH than the free enzyme; its pH stability at high pH was also much better.The thermal stability of the gel‐entrapped enzyme was studied and found to be 14 days at 22°C and 65 min at 45°C.
The functional role of lipids in hydrocarbon assimilation
Authors: Hug H. , Blanch H. W. , Fiechter A. 
Published: December 2004

AbstractThe yeast Candida tropicalis utilizes both glucose and hydrocarbons as sole carbon sources. When grown on hydrocarbons, the cells contain twice as much lipid as when grown on glucose. In transient continuous culture experiments, following a substrate change from glucose to hexadecane, an adaption phase occurred. During this phase the lipid concentration per cell increased greatly. It is proposed that a high cellular lipid concentration is necessary for hydrocarbon assimilation, and this is not just a reflection of the lipophilic nature of the substrate.
Reduction of contamination in an industrial fermentation plant
Authors: Bartholomew W. H. , Engstrom D. E. , Goodman N. S. , O'Toole A. L. , Shelton J. L. , Tannen L. P. 
Published: December 2004

AbstractInformation is presented concerning revisions of the fermentation air system equipment which improved the sterility situation in the production of monosodium glutamate.Basically, the revision were a relocation and elevation of the intake to the air compressors and installation of a retention chamber after the compressors to take advantage of the heat of compression.The extended high temperature retention ensures sterile air to the final air filter before the fermentor. Contamination losses—mainly from phage—have been materially reduced relative to the level prevailing before the change.
Enzyme catalysis in the presence of nonaqueous solvents using chloroperoxidase
Authors: Cooney Charles L. , Hueter John 
Published: December 2004

AbstractStudies exploring the effect of two nonaqueous solvents on enzyme activity were done using chloroperoxidase as a model system. Chloroperoxidase produced by Caldariomyces fumago is a bifunctional enzyme with halogenating activity at pH 3 and peroxidation activity at pH 5 to 6. Methanol affected both of these activities similarly. Furthermore, methanol and the halogen acceptor, monochlorodimedon, competitively inhibit the reaction. These results are discussed in terms of the site of action of methanol. At 10% methanol concentration, the enzyme retained up to 33% of its activity depending on the monochlorodimedon concentration. Dimethylsulfoxide at 10% concentration permitted up to 47% retention of activity. Its effects on the enzyme are more complex than methanol and are discussed in terms of a transitory inactivation of the enzyme.
Recovery of erythropoietin from anemic sheep plasma
Authors: Hancher C. W. , Hall R. F. , Ryon A. D. , Kelmers A. D. 
Published: December 2004

AbstractA method is described for the large‐scale preparation of erythropoietin from anemic sheep plasma. DEAE‐cellulose and carboxymethylcellulose column chromatography was used to prepare Step II erythropoietin. A total of 168 sheep yielded 499 liters of plasma from which 323,000 IU of Step II erythropoietin was obtained.
An enzyme rate equation for the overall rate of reaction of gel‐immobilized glucose oxidase particles under buffered conditions. II. Two limiting substrates
Authors: Atkinson B. , Lester D. E. 
Published: December 2004

AbstractThe overall rate of reaction of gel‐immobilized glucose oxidase particles in buffered media has been investigated theoretically under two substrate diffusion limited conditions by the numerical solution of the diffusion equations. It has been found that the Enzyme Rate Equation (Atkinson and Lester), Biotechnol. Bioeng., 16, 1299 (1974), together with an analytical solution which describes the asymptotic conditions associated with a large particle size, provides an adequate estimation of the values resulting from the numerical solution outside the region of the parameter space defined by 0.4 < Mg′, M0′ < 10.When the dimensionless parameter (B0′/Bg′)(Mg′2/M0′2) is greater than unity the overall rate of reaction is limited principally by the external concentration and when the parameter has a value less than unity, by the external oxygen concentration.The results are generally applicable to enzymes whose kinetics are similar to those of glucose oxidase or for which the equation describing glucose oxidase kinetics provides an adequate curve‐fit of experimental data.
Immobilized enzyme catalysis with reaction‐generated pH change
Authors: Bailey J. E. , Chow Mary T. C. 
Published: December 2004

AbstractMany enzyme‐catalyzed reactions involve the liberation or consumption of hydrogen ions. In this paper a mathematical model is employed to investigate how such reactions behave when the enzyme is immobilized. Shifted pH optima, disappearance of an optimum pH, insensitivity to bulk pH, and very large effectiveness factors are some of the phenomena which appear as a result of pH coupling between the reaction and the enzyme's activity. Several of the qualitative features revealed by the model are consistent with earlier experimental observations. In addition, preliminary guidelines for optimal choice of enzyme support are suggested.
An annular bound‐enzyme reactor
Authors: Emery A. , Sorenson J. , Kolarik M. , Swanson S. , Lim H. 
Published: December 2004

AbstractA column reactor with an annular cross section was formed by rolling up DEAE cellulose paper and a screening spacer. Glucoamylase was attached by ion adsorption. For the spacer used, pressure drop was very low, suggesting that this form may be useful with feed streams that are not completely particle‐free. Tests of this reactor at the high substrate concentrations characteristic of commercial reactors showed very little diffusional resistance, exhibiting zero‐order behavior over most of the concentration range. At low concentrations, the reactor had an apparent “half‐order” behavior caused by diffusional limitation in the paper. In this range, flow rate influenced the reaction rate, showing that mass transfer in the main stream also is a contributing factor in this range. Because of the high concentrations and the low Michaelis constant (0.0011 M) the reactor does not show first‐order behavior, even at very high conversions. The design of a plant‐scale reactor was formulated from these data. The increase in the quantity of enzyme necessary to compensate for the effects of diffusion was only a few percent.Two reactors were formed with sheets nonporous to the enzyme, binding the enzyme with cyanogen bromide after forming the reactor. The amount of enzyme bound was about one monolayer, and there appeared to be no diffusional limitations, even at low substrate concentrations.
Assessment of methanogenie activity in anaerobic digestion: Apparatus and method
Authors: Van Den Berg L. , Lentz C. P. , Athey R. J. , Rooke E. A. 
Published: December 2004

AbstractAn apparatus is described for the rapid measurement and recording of methanogenic activity in anaerobic fermentations, and its application is demonstrated in the evaluation of the anaerobic contact process, using pear waste. The method is based on recording the rate of manometer liquid displacement in a Warburgtype vessel by means of optical sensors, appropriate electronic circuitry, and an event marking recorder or time‐interval printer. Optimum conditions for measuring methanogenic activity included a pH of 6.7–6.9, a final phosphate buffer concentration of 0.07–015M, and formic and acetic acid contents of over 500 and 200 mg/liter, respectively. In comparisons of fermenter liquid and settled effluent, methanogenic activity can be assumed to be proportional to the number of methane formers present. The apparatus should be generally useful in recording rates of gas production or consumption.
Enzymatic hydrolysis of waste cellulose
Authors: Mandels Mary , Hontz Lloyd , Nystrom John 
Published: December 2004

AbstractWaste cellulose was a suitable carbon source for cellulose production by Trichoderma viride. The enzyme can be produced in submerged fermentation using newspaper as a growth substrate. A variety of pure and complex cellulosic materials were hydrolyzed by culture filtrates. Saccharification of 5% slurries after 48 hr ranged from 2–92%. The rate and extent of hydrolysis was controlled by degree of crystallinity, particle size, and presence of impurities. Newspaper was used to evaluate methods for the pretreatment of substrate. The best pretreatment was ball milling which gave good size reduction, maximum bulk density, and maximum susceptibility. Hammer milling, fluid energy milling, colloid milling, or alkali treatments were less satisfactory. Dissolving cellulose in cuprammonium, or carbon disulfide (Viscose) and then reprecipitating gave a susceptible, but low bulk density product. However the susceptibility was lost if the substrate was dried. Because of costs, low bulk density, necessity of keep ing the substrate wet, and generation of chemical waste streams dissolving cellulose to increase reactivity does not seem a practical approach.Cellulose fractions separated from municipal trash or agricultural residues such as milled fibres from bovine manure are promising substrates for conversion.
The influence of alkali and heat treatment on yeast protein
Authors: Lindblom Marianne 
Published: December 2004

AbstractThe soluble components in disintegrated cells of Saccharomyces cereivisiae have been characterized by means of extraction, centrifugation, dialysis, and gel filtration. The influence of alkali and heat treatment on the protein and RNA in the soluble fraction from disintegrated yeast cells and on functional properties of protein concentrates have been studied.After water extraction and centrifugation at 100000 g 42% of the nitrogen containing components of the disintegrated cells were recovered in the supernatant. By extraction at pH 11.5 an additional 31% of the nitrogen was solubilized. Half of the water‐soluble nitrogen‐containing components has a molecular weight lower than 5000. In the water‐ and alkali‐soluble fractions about 80% of each amino acid was recoveredThe water‐soluble protein was separated into 3 fractions by gel filtration on Sephadex G 200. The major portion of the protein had a molecular weight about 100,000. The amount of protein in this fraction was decreased after treatment at increasing pH and temperature. No degradation of protein to low molecular peptides occurred. The amount of RNA in the soluble fraction was only slightly influenced by alkali treatment and by heat treatment at pH 7.5 in the presence of 5% NaCl. RNA was not degraded to low molecular components of the treatments.The solubility of protein concentrates decreased after treatment at alkaline pH and after heat precipitation.
Preparation of an immobilized two‐enzyme system, β‐amylase–pullulanase, to an acrylic copolymer for the conversion of starch to maltose. III. Process kinetic studies on continuous reactors
Authors: Mårtensson Kaj 
Published: December 2004

AbstractKinetic studies on the parameters influencing the potential industrial application of an immobilized two‐enzyme system of β‐amylase and pullulanase for conversion of starch to a product with high maltose content, have been performed. The apparent Michaelis constant, the apparent product inhibitor constant, and the activation energy have been determined for the immobilized preparation and compared to the values for the corresponding soluble enzyme system. The catalytic activity of the immobilized enzymes was studied in a plug‐flow reactor and a continuous feed stirred tank reactor. Mathematical models for these reactors have been formulated and adapted to fit the experimental data. Comparisons of the reactor efficiencies were made and the conditions were found to be such as to favor the plug‐flow reactor. Results on operational stability tests at different temperatures and substrate concentrations are given.