bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immobilized xanthine oxidase: Kinetics, (in)stability, and stabilization by coimmobilization with superoxide dismutase and catalase
Authors: Tramper Johannes , Müller Franz , Van Der Plas Henk C. 
Published: December 2004

AbstractMilk xanthine oxidase was immobilized by covalent attachment to CNBr‐activated Sepharose 4B and by adsorption to n‐octylamine‐substituted Sepharose 4B. The amounts of activity immobilized for the two preparations were 30 and 90%, respectively. The pH optima for free and adsorbed xanthine oxidase were at 8.6 and 8.2, respectively. Both free and immobilized xanthine oxidase show substrate inhibition. The apparent inhibition constant (Ki′) found for adsorbed xanthine oxidase with xanthine as substrate was higher than the Ki for the free enzyme, which was shown to be due to substrate diffusion limitation in the pores of the carrier beads (internal diffusion limitation). Higher substrate concentrations, as desirable for practical application in organic synthesis, can therefore be used with the immobilized enzyme without decreasing the rate. As a result of the internal diffusion limitation the apparent Michaelis constant (Km′) for adsorbed xanthine oxidase was also higher than the Km for the free enzyme. Immobilized xanthine oxidase was more stable than the free enzyme during storage at 4 and 30°C. Both forms rapidly lost activity during catalysis. The loss was proportional to the amount of substrate converted. Coimmobilization of xanthine oxidase with superoxide dismutase and catalase improved the operational stability, suggesting that O2− and H2O2 side‐products of the enzymatic reaction were involved in the inactivation. Coimmobilization with albumin also had some stabilizing effect. Complete surrounding of xanthine oxidase by protein, however, by means of etrapment in a glutaraldehyde‐crosslinked gelatin matrix, considerably enhanced the operational half‐life. This system was less efficient than the Sepharose preparations either because much activity was lost during the immobilization procedure and/or because it had poor flow properties. Xanthine (15 mg)was converted by an adsorbed xanthine oxidase preparation and product (uric acid) was isolated in high yield (84%).
Cellulase production and ammonia metabolism in Trichoderma reesei on high levels of cellulose
Authors: Sternberg David , Dorval Sheila 
Published: December 2004

AbstractTrichoderma can be cultured in stirred‐tank fermentors on high (8%)cellulose concentrations without increasing the salt concentration of the medium when NH4OH is used to control pH and as a nitrogen source. Approximation 90% of the ammonia consumed by the organism can be added as NH4OH. The advantage of using high concentrations of cellulose is that culture filtrates with greater cellulase activity are obtained. The advantage of a low salts medium is that unwanted solutes in the final enzyme preparation are reduced. The appearance of cellulase in the medium occurs later than net ammonia uptake so that only 20% of the final amount of cellulase has appeared when 80% of the maximum amount of ammonia has been consumed.
Nitrogenase activity of immobilized Azotobacter vinelandii
Authors: Seyhan E. , Kirwan D. J. 
Published: December 2004

AbstractAs part of a program to investigate the use of biological nitrogen fixation for fertilizer ammonia production, an investigation into the immobilization of the aerobic, nitrogen‐fixing bacterium, Azotobacter vinelandii was undertaken. Immobilization was accomplished by adsorption onto an anionic exchange cellulose (Cellex E)with loadings as high as 1011cells/g resin. Immobilized cell preparations were tested under both batch and continuous‐flow conditions. Nitrogenase activity as high as 4200 nmol/min g resin were observed as measured by the acetylene reduction assay. Immobilized cells retained their activity for as long as 177 hr in a continuous‐flow reactor. Activity loss appeared to be related to the development of a variant strain.
Time scale in the dynamics of continuous cultivation of microorganisms
Authors: Minkevich I. G. , Utkina L. I. 
Published: December 2004

AbstractThe existence of rapid and slow transients in the continuous culture of microorganisms when limited by one of the nutrients is revealed on the basis of a new method of mathematical analysis that separates these rapid and slow transients. The slow transient occurs along one and the same line of slow movement (LSM) independent of the initial state of the culture. This line is situated in the “substrate concentration S – biomass concentration X” coordinate system and rigidly connects these concentrations. When the initial values of S and X do not lie on this line, the rapid process occurring before the slow one leads the culture to LSM. Arrival to LSM occurs owing to alteration of S at almost constant X. The biomass concentration is always a slow variable but tne substrate concentration is both a rapid and a slow variable. A number of regularities of this time hierarchy are analyzed. A comprehensive description of the dynamics of continuous cultivation of microorganisms including different ways of supplying limiting nutrients is presented. Phaseplane plots of microbial cultures and the families of isochrones (lines making it possible to determine exactlythe transient duration) are given. The isochrone theory is described in the appendix.
Improved nonporous magnetic supports for immobilized enzymes
Authors: Halling P. J. , Dunnill P. 
Published: December 2004

AbstractNi powders coated by deposition of TiO2 or controlled oxidation to NiO develop substantial resistance to corrosion. Chymotrypsin immobilized to these coated Ni supports shows very high stability of activity on storage. Chymotrypsin immobilized by adsorption and glutaraldehyde crosslinking was fairly rapidly eluted under operational conditions in the presence of substrate. If 3‐aminopropyltriethoxysilane (APS) was used to produce a covalent linkage, desorption of enzyme still occurred because of relatively unstable bonding of the silane to the oxide surface. A more stable attachment was produced by joining together many silane links with a layer of polyglutaraldehyde. The mechanism of action of APS as a coupling agent under these conditions is discussed. γ‐Fe2O3, and particularly a Mn‐Zn ferrite, are suitable magnetic support materials available with smaller particle sizes. Particles below 1 μm give the expected higher specific activities of immobilized enzymes.
Purification and properties of milk‐clotting enzyme from Bacillus subtilis K‐26
Authors: Rao Lavu Krishna , Mathur D. K. 
Published: December 2004

AbstractA milk‐clotting enzyme from Bacillus subtilis K‐26 was purified by gel filtration and ion‐exchange chromatography resulting in a 24‐fold increase in specific activity with an 80% yield. Polyacrylamide gel electrophoresis and ultracentrifugel analysis revealed that the purified enzyme was homogeneous and had a molecular weight of 27,000 and a Km of 2.77mg/ml for κ‐casein. The enzyme was most stable at pH 7.5 and showed increasing clotting activity with decrease in milk pH up to 5.0. The maximum milk‐clotting activity was obtained at 60°C, but the enzyme was inactivated by heating for 30 min at 60°C. The enzyme was irreversibly inhibited by EDTA and unaffected by DFP. Heavy‐metal ions (Hg2+, Pb2+) inactivated the enzyme.
Process characteristics of cell lysis mutants of Saccharomyces cerevisisae
Authors: Boudrant Joseph , DeAngelo Joseph , Sinskey Anthony J. , Tannenbaum Steven R. 
Published: December 2004

AbstractSeveral temperature‐sensitive lysis mutants of Saccharomyces cerevisiae were selected according to their ability to release alkaline phosphatase when incubated at a nonpermissive temperature. For two mutants, cell lysis and release of alkaline phosphatase reached a maximum when cells in the logarithmic growth phase were shifted to the ncnpermissive temperature. Morphological changes, as well as changes in macromolecular composition of the cells, were observed. Growth is necessary and oxygen is important for the expression of cell lysis at the nonpermisseve temperature.
Effect of environmental parameters on the efficiency of biodegradation of basalt rock by fungi
Authors: Mehta A. P. , Torma A. E. , Murr L. E. 
Published: December 2004

AbstractThe biodegradation of an aluminum‐bearing (basalt) rock by Penicillium simplicissimum has been investigated. This organism grows on a sugar substrate and releases organic acid compounds. These acids interact with the mineral matter and cause their partial decomposition. The dissolved metals are then complexed by the excess organic acids. The activity of the fungi was found to be optimum at an initial pH 7 and in the presence of 5% (w/v) substrate concentration. In 30 days of leaching almost 20% of the aluminum in the rock was solubilized and the pH was decreased from 7 to less than 3.5 in the inoculated flasks. The controls showed less than 1% of the aluminum solubilized and the final pH dropped to only 6.8. A surface characterization study performed by scanning electron microscopy indicated that the specific mineralogical phases containing aluminum and iron within this host rock were preferentially corroded. The mineral phases containing olivine and plagioclase were found to be least resistant, while phases containing titanium were most resistant to the acids released by the fungi.
Mathematical model for enzymatic hydrolysis and fermentation of cellulose by Trichoderma
Authors: Peitersen Nicolai , Ross Edward W. 
Published: December 2004

AbstractThis paper describes a mathematical model for the enzymatic hydrolysis and fermentation of cellulose by Trichoderma reesei. The principal features of the model are the assumption of two forms of cellulose (crystalline and amorphous), two sugars (cellobiose and glucose), and two enzymes (cellulase and β‐glucosidase). An inducer–repressor–messenger RNA mechanism is used to predict enzyme formation, and pH effects are included. The model consists of 12 ordinary differential equations for 12 state variables and contains 38 parameters. The parameters were estimated from four sets of experimental data by optimization. The results appear satisfactory, and the computer programs permit simulation of a variety of system changes.
Immobilization of microbial cells containing NAD‐kinase
Authors: Hayashi Toru , Tanaka Yoshikazu , Kawashima Koji 
Published: December 2004

AbstractMicrobial cells having NAD‐kinase activity, Brevibacterium ammoniagenes, were immobilized by the radiation‐copolymerization method under low temperature with the activity recovery of more than 80%. Compared to the native microbial cells the immobilized cells were more stable against heat and pH change. The immobilized cells were subjected to the 5 hr reaction repeatedly 20 times without any activity loss.
Ethanol in brazil: Brief summary of the state of industry in 1977
Authors: Lindeman Louis Robert , Rocchiccioli Carlo 
Published: December 2004

AbstractThis paper presents a summary of present agricultural production of ethanol in Brazil. The highlights of the national program instituted in 1975 to increase production with the aim of extending automotive gasoline are described. Process descriptions are given for present plants for both cane sugar and manioc root fermentation routes.
Dextran biosynthesis and dextransucrase production by continuous culture of Leuconostoc mesenteroides
Authors: Lawford G. R. , Kligerman A. , Williams T. , Lawford H. G. 
Published: December 2004

AbstractLeuconostoc mesenteroides NRRL B‐512(F) was grown in continuous culture under conditions of energy‐limited growth. The extracellular enzyme dextransucrase (sucrose: 1,6‐α‐D‐glucan 6‐α‐glucosyltransferase EC 2.4.1.5), was not detected in glucose‐or maltose‐limited cultures. Under Conditions of sucrose‐limited growth, the enzyme activity of the cell‐free culture supernatant increased with increasing dilution rate only after the critical concentration of enzyme inducer (sucrose) in the chemostat had been achieved. The appearance of fructose in the effluent of the sucrose‐limited chemostat at higher dilution rates indicated that sucrose was being diverted to dextran biosynthesis. The competition between bacteria and extracellular enzyme for the common substrate sucrose represents an inefficiency in the system of enzyme production. Dextransucrase was isolated from the cell‐free culture supernatant by ammonium sulfate precipitation and DEAE‐cellulose chromatography. The enzyme preparation exhibited both dextran biosynthetic activity and an invertase‐like activity. The biosynthetic efficiency was increased by decreasing the temperature from 30 to 10°C. The enzyme was irreversibly denatured by prolonged incubation in the absence of Ca2+.
Production of high‐quality edible protein from Candida yeast grown in continuous culture
Authors: Lawford G. R. , Kligerman A. , Williams T. , Lawford H. G. 
Published: December 2004

AbstractCandida utilis NRRL Y‐900 was grown in aerobic continuous culture with cane molasses as the source of the growth‐limiting carbon. At 1% reducing sugar in the chemostal (10 liter working volume) feed medium, addition of Zn (25μM) to a minimal salts medium resulted in an increase in the biomass productivity of the chemostat from 1.7 to 2.6 g/liter/hr with a growth yield of 0.55 g dry biomass/g reducing sugar utilized at Dmax. On the average, the yeast biomass was 50–55% protein. At SR > 2% sugar, the biomass productivity was limited by the oxygen supply. With O2‐supplemented aeration (at SR = 4.2%)the maximum biomass productivity Was 7.25 g/liter/hr. Aerobic ethanol production was not observed. A highquality undenatured protein fraction was isolate from the yeast homogenate by isoelectric precipitation at pH 4.5. Contaminating nucleic acid was removed as an insoluble complex by chelation with an organic cation (cetavlon). The final protein product contained about 3% RNA (DWB) and was suitable for use as a food additive.
Rapid ethanol fermentation of cellulose hydrolysate. II. Product and substrate inhibition and optimization of fermentor design
Authors: Ghose T. K. , Tyagi R. D. 
Published: December 2004

AbstractHigh concentrations of both ethanol and sugar in the fermentation broth inhibit the growth of yeast cells and the rate of product formation. Inhibitory effects of ethanol on the yeast strain Saccharomyces cerevisiae NRRL‐Y‐132 were studied in batch and continuous chemostat cultures. Growth was limited by either glucose or ethanol. Feed medium was supplemented with different ethanol concentrations. Ethanol was found to inhibit growth and the activity of yeast to produce ethanol in a noncompetitive manner. A linear kinetic pattern for growth and product formation was observed according to μ = μm (1 – P/Pm) and v = vm (1 – P/Pm′), where μm is the maximum specific growth rate at P = 0 (hr−1); Pm is the maximum specific product formation rate at P = 0 (hr−1); Pm is the maximum ethanol concentration above which cells do not grow (g/liter); Pm′ is the maximum ethanol concentration above which cells do not produce ethanol (g/liter). Substrate inhibition studies were carried out using short‐time experimental techniques under aerobic and anaerobic condition. The degree of substrate inhibition was found to be higher than that has been reported for ethanol fermentation of pure sugar. The kinetic relationships thus obtained were used to compute growth, substrate utilization, and alcohol production patterns and have been discussed with reference to batch and continuous fermentation of enzymatically produced bagasse hydrolysate.
Method for continuous purification of biological material using immunosorbent
Authors: Hughes James J. , Charm Stanley E. 
Published: December 2004

AbstractA mechanical device for the continuous purification of biological material using immunosorbent was developed. The system consists of heat‐sealed nylon pouches containing agarose‐bound antibody, attached to an endless 35 mm wide Mylar belt that passes through four chambers sequentially. The biological material is bound and dissociated, and the immobilized antibody is regenerated for repeated isolation and purification of antigen. The belt design incorporates features to minimize carry‐over between chambers and prevent damage to the agarose‐bound antibody in repeated passes through the system. An existing batch method for the purification of human placental alkaline phosphatase using immobilized rabbit antisera was adapted to continuous purification in the device. The belt contained a low affinity immunosorbent and made five complete passes through the system. A decrease in antigen binding capacity between free immunosorbent suspensions and belt immunosorbent in pouches was observed. This was shown to be the result of the diffusion resistance offered by the pouch and the short exposure times of each pouch in the chambers. A decrease in antigen binding capacity between successive belt passes was also observed, and resulted from the inability of the agarose in the pouches to resuspend completely after each pass. The low efficiency of the agitation method and the roller device used to squeeze the pouches were the reasons for this deficiency.
Analysis of pH‐stat continuous cultivation and the stability of the mixed fermentation in continuous yogurt production
Authors: MacBean R. D. , Hall R. J. , Linklater P. M. 
Published: December 2004

AbstractA pH‐stat fermentor is a continuous cultivator in which the feed rate is controlled to maintain a constant pH, i.e., end‐product acid concentration. This fermentor has application to the continuous cultivation of lactic acid‐producing organisms in milk‐based media. The equations describing the operation of this fermentor are developed. It is shown that, where the limiting substrate is the carbon and energy source, the operation of the fermentor is essentially equivalent to that of a turbidostat. In contrast to this, where the carbon and energy source is in excess and growth is limited by another substrate, pH‐state fermentation is stable both in regions of substrate excess, where D = μmax, comparable with turbidostat operation, and substrate limitation where D < μmax, comparable with chemostat operation. These conditions are met in milk‐based media. An analysis is presented, allowing the prediction of the degree of substrate limitation, cell density, and dilution rate in a pH‐stat fermentor from batch‐growth kinetics. This was confirmed using experimental data for the growth of Streptococcus thermophilus TS2 and Lactobacillus LB1 in skim milk. Stable simultaneous growth of two organisms in continuous culture occurs if their growth rates are determined by separate conditions, so that, at steady state, their growth rqtes are separately madeequal to the dilution rate. It is then predicted, and confirmed by experiment, that a mixed culture of S. thermophilus TS2 and L. bulgaricus LB1 in a pH‐stat continuous fermentor in yogurt mix at pH 5.5 would be stable with the growth of L. bulgaricus being substrate unlimited and the fermentor operting with D = μmax for L. bulgaricus LB1, and the growth of S. thermophilus TS2 being substrate limited so that its growth rate is equal to the existing dilution rate. Finally, it is predicted and confirmed by experiment that if the conditions are altered so that the growth of S. thermophilus TS2 is substrate unlimited the stable association is broken down, the fermentor operates with D approaching μmax for S. thermophilus TS2, and L. bulgaricus LB1 is washed out to the level maintained by wall growth.
Analysis of denitrification with a completely submerged pilot‐scale rotating biological contactor
Authors: Soyupak S. , Murphy K. L. , Jank B. E. 
Published: December 2004

AbstractThe hydraulic characteristics and the denitrifying capacity of a single‐stage 0.5 m diam completely submerged rotating biological contactor were studied. A two compartment model was proposed and fitted the data obtained from pulse dye applications at two different flow rate. Denitrification rates with an influent C:N ratio at 1.5:1 proved to be independent of NO3 + NO2‐N concentration. The pooled denitrification data obtained under the two different flow rates could be fitted by an Arrhenius relationship for temperature over the range of 5 to 25°C. The activation energy was 16500 cal/g−mol. A substantially higher volumetric removal capacity was observed than has previously been reported for either suspended or supported denitrifying systems.
Physical Studies on Cell Immobilization Using Calcium Alginate Gels
Authors: Cheetham Peter S. J. , Blunt Kevin W. , Bocke Christopher 
Published: December 2004

AbstractColumns of calcium alginate gel pellets have excellent physical properties when used as a cell immobilization support. Columns of pellets were very resistant to compression and abrasion during passage of high concentrations of sucrose at high flow rates, but if the pellets were formed using low alginate and Ca2+ concentrations, compression occurred and flow out of the column was reduced and pressure built up. Transfer of sucrose into the pellets was controlled by internal diffusion, the rate of diffusion being increased by reductions in the alginate and Ca2+ concentrations used for immobilization and by the presence of entrapped active cells. Some leakage of cells occurred during use especially when cell division of the entrapped cells took place, but leakage could be minimized by using more highly polymerized pellets. Therefore, immobilization conditions can be chosen so as to form strong pellets, possessing high substrate transfer rates and low rates of cell leakage.
Large‐scale preparation of a lectin from sunn hemp seeds (Crotalaria juncea)
Authors: Ersson Bo 
Published: December 2004

AbstractA procedure for large‐scale preparation of a lectin from Crotalaria juncea seeds is described. The method involve fractionation by pH‐ and ammonium sulfate precipitation followed by biospecific affinity chromatography. The adsorbent used for the affinity chromatography was prepared by coupling galactose to Sepharose 6B activated with divinylsulfone. A comparison of different apparatus and techniques involved in the preparation is discussed. The yield and quality of the lectin prepared at a large scale were comparable with laboratory‐scale preparation. From 50 kg Crotalaria juncea beans, 14.4 g Crotalaria lectin were obtained.