bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational analysis of dolastatin 10: An nmr and theoretical approach
Authors: Benedetti E. , Carlomagno T. , Fraternali F. , Hamada Y. , Hayashi K. , Paolillo L. , Shioiri T. 
Published: December 2004

AbstractA solution conformational analysis of dolastatin 10, a powerful antineoplaslic agent, has been carried out by means of nmr techniques and theoretical calculations. 1H mono‐ and bidimensional nmr experiments, as well as 1H‐13C heterocorrelated spectra, have been performed on CD2Cl12 solutions. The most interesting nmr data is a huge shielding of the aCH (25) proton of the Dov residue, suggesting the presence of an interaction between the N‐terminal and the aromatic C‐terminal ends of the molecule.The possibility of a head‐to‐tail intermolecular association having been discarded, the presence of a series of preferred folded conformation has been hypothesized. Conformational theoretical analysis supports the nmr hypothesis of a folded peptide‐like molecule, and a series of possible conformers in good agreement with the experimental data have been analyzed. © 1995 John Wiley & Sons, Inc.
Microbial production of amino acids. II. The influence of carbon and nitrogen sources and metal ions on growth of Ustilago maydis (DC.) Cda. and on lysine and threonine production
Authors: Kurz W. G. , Ericson L.‐E. 
Published: December 2004

AbstractThe ability of Ustilago maydis (DC.) Cda. to grow and to produce lysine and threonine was investigated in shake flask cultures. Growth and production of lysine and threonine increased markedly when aeration was increased. The optimal ratio of glucose to diammonium phosphate in the medium seemed to be approximately 10:1. Ammonium phosphate, ammonium sulfate, ammonium chloride, ammonium nitrate, sodium nitrate, urea, aspartic acid, glutamic acid, and glycine were readily used as nitrogen sources. Growth and amino acid production was poor on ammonium carbonate, ammonium acetate, ammonium citrate, trimethylamine, and betaine.U. maydis (DC.) Cda. was found to grow on a number of different carbohydrates. Besides D‐glucose the organism could utilize D‐mannose, D‐galactose, D‐fructose, L‐arabinose, D‐xylose, D‐ribose, sucrose, maltose, and the polyalcoholes D‐sorbitol, D‐mannitol, and i‐inositol. Pectin, dextrin, and corn starch treated with α‐amylase could also be used but not untreated corn starch or lactose, cellobiose, D‐sedoheptulose, glycerol, or D‐glucosamine. The formation of lysine and threonine was better with disaccharides and hexoses than with pentoses.No specific effects on the formation of lysine and threonine could be observed from changes in the concentration of calcium, sodium, potassium, magnesium, zinc, iron, copper, manganese, cobalt, or molybdenum. The requirement of metal ions for growth is discussed.
Preparation and characterization of isolubilized L‐amino acid oxidase
Authors: Weetall H. H. , Baum G. 
Published: December 2004

AbstractThe enzyme L‐amino acid oxidase of Crotalus adamanteus was covalently coupled to porous 96% silica glass particles. The insolubilized enzyme was active on several L‐amino acids including: leucine, isoleucine, cysteine, phenylalanine, tryptophane, and methionine. No activity was observed with D‐amino acids, L‐asparagine, or L‐proline. Maximum activity was observed at pH 7.8. Stability of the enzyme derivative was demonstrated by continuous operation of an enzyme column for 35 days, during which the bound enzyme oxidized over 5000 times its own weight of substrate.
Design and evaluation of a system for thermal decontamination of process air
Authors: Chatigny M. A. , Sarshad A. A. , Pike G. F. 
Published: December 2004

AbstractAerobiology studies at the Naval Biological Laboratory require use of a vacuum system to provide safe disposal of air contaminated with pathogenic, microorganisms. A system for thermal decontamination of this process air has been installed and tested. The system uses a natural gas burner to heat approximately 550 cfm of air to temperatures exceeding 750°F. Tests showed a reduction in number of acrosolized viable hardy spores (Bacillus subtilis var. niger) of more than 8 logs at design flow rates. The kill rate (D values) measured in this system is somewhat higher than those reported by other workers. The annual owning and operating cost of the system is approximately $9000.
Application of ultrafiltration for enzyme. Retention during continuous enzymatic reaction
Authors: Butterworth T. A. , Wang D. I. C. , Sinskey A. J. 
Published: December 2004

AbstractIn most enzymatic reactions, batch or continuous, separation of the enzyme for reuse is difficult if not impossible. A process will be presented in which an Ultrafiltration membrane serves to separate the reaction products from the enzyme and the substrate. In this manner the enzyme may be retained and re‐used. Furthermore, under these conditions, the enzyme need only be present in catalytic amounts regardless of the amount of product produced.Under proper operating conditions and proper ultrafiltration membrane selection, a pure solution of α‐amylase from Bacillus subtilis may be retained with no loss in enzyme activity over a test period of 30 hr after steadystate has been achieved. In the presence of substrate, the membrane support and ultrafiltration cell serve as the reaction vessel for the hydrolysis of starch. The substrate is continuously pumped into the cell under constant ultrafiltration pressure. The di‐, oligo‐, and polysaccharides formed from the enzyme reaction then either pass through the membrane as products or are retained. The molecular weight distribution of the products is dependent on the nominal molecular weight cut‐off of the membrane, absolute ultrafiltration pressure, enzyme‐to‐substrate ratio, temperature, and residence time of the substrate in the reactor. In addition to the partial hydrolysis of starch by α‐amylase, some preliminary findings on the complete hydrolysis of starch by glucoamylase will also be presented. In these latter studies, the substrate may be completely hydrolyzed to glucose units.
Degradation and mineralization of petroleum by two bacteria isolated from coastal waters
Authors: Atlas Ronald M. , Bartha Richard 
Published: December 2004

AbstractWithin the framework of a study on the oil biodegradation potential of the sea the ability of a Flavobacterium sp. and Brevibacterium sp. to metabolize a paraffinic crude oil and a chemically defined hydrocarbon mixture was investigated. Major components of the crude oil were identified by combination gas chromatography and mass spectrometry. The rate and extent of total hydrocarbon biodegradation was measured. In addition, CO2 evolution from the crude oil was continuously monitored in a shaker‐mounted gas train arrangement. Degradation started after a 2 to 4 day lag period, and reached its maximum within two weeks. At this time up to 60% of the crude oil and 75% of the model hydrocarbon mixture, each added at the level of 1 ml per 100 ml artificial sea water, were degraded. Mineralization(conversion to CO2) was slightly lower due to formation of products and bacterial cell material. n‐Paraffins were preferentially degraded as compared to branched chain hydrocarbons. Biodegradation of n‐paraffins in the range of C12 to C20 was simultaneous; no diauxie effects were observed.
Effects of growth rate and influent substrate concentration on effluent quality from chemostats containing bacteria in pure and mixed culture
Authors: Grady C. P. L. , Harlow L. J. , Riesing R. R. 
Published: December 2004

AbstractStudies were performed using pure cultures of A. acrogenes and E. coli and a heterogeneous microbial population growing in carbon‐limited chemostats with glucose as the sole carbon and energy source. A two‐level factorial experimental design was employed to test the hypothesis that the concentration of growth‐limiting substrate in a chemostat is controlled by the growth rate alone and is independent of the concentration of substrate entering the reactor. The pure culture experiments showed that the conclusions depend upon the measurement employed for growth‐limiting substrate. When the concentration of glucose was measured directly, the hypothesis was found to be true within the limits of the study (500–1500 mg/liter). However, if the chemical oxygen demand (COD) test was used as the measure of growth‐limiting substrate the hypothesis was found to be false. When heterogeneous cultures were employed the hypothesis was false regardless of the technique used to measure the concentration of growth‐limiting substrate. Nevertheless, it was possible to generate regression equations which described the interactions among influent COD, growth rate, and effluent COD with a high level of correlation.
Growth models of cultures with two liquid phases. VIII. Experimental observations on droplet size and interfacial area
Authors: Prokop A. , Ludvik M. , Erickson L. E. 
Published: December 2004

AbstractBecause of the importance of the drop she distribution and interfacial area of the dispersed liquid phase in hydrocarbon fermentations, experiments were carried out to determine the drop size distribution and the interfacial area during batch fermentations ofCandida lipolyticaon gas oil and onn‐hexadecane dissolved in dewaxed gas oil. The effects of cell concentration and dispersed phase volume fraction on size distribution and interfacial area were investigated. Measurements of interfacial tensions, densities, viscosities, and fatty acid concentrations were also made. The results show that the size distribution is skewed and that the Sauter mean diameter is in the range of 10 to 30 μ. Both the Sauter mean diameter and the interfacial area increased during the course of a batch fermentation; however, they decreased at the end of the fermentation. The interfacial area also increased with inoculum size.
Invertase covalently coupled to porous glass: Preparation and characterization
Authors: Mason R. D. , Weetall H. H. 
Published: December 2004

AbstractThe enzyme invertase has been covalently coupled to porous glass particles. The product is extremely stable over a long period of time. Kinetic values for the immobilized enzyme are similar to the native enzyme. Excellent enzymatic activity for the immobilized enzyme was exhibited over a broad pH range. The immobilized enzyme when continuously operated for one month was found to have an operational half‐life of over 40 days.
Kinetic studies of C. pyrenoidosa using 94% 13C CO2
Authors: Fowler Eric B. , Adams W. H. , Christenson C. W. , Kollman V. H. , Buchholz J. R. 
Published: December 2004

AbstractThe alga Chlorella pyrenoidosa has been grown in mass quantities on 94 at. % 13CO2. The algal cells have been labeled to the 90 at. % 13C level. Neither inhibition nor a requirement for adaptation was encountered; changes in morphology were not evident. A statistically significant increase in mass of cells produced in the presence of 13CO2 was observed.
Collagen‐enzyme complex membranes and their performance in biocatalytic modules
Authors: Wang S. S. , Vieth W. R. 
Published: December 2004

AbstractCollagen was used as carrier for the immobilization of invertase, lysozyme, urease, glucose oxidase, penicillin amidase, and glucose isomerase. Immobilization was accomplished by either impregnation of a preswollen collagen membrane with enzyme solution or electrocodeposition of collagen and enzyme from a collagen dispersion containing dissolved enzyme. The collagen‐enzyme complexes prepared are in membrane form.Membranous collagen‐enzyme complexes were used to construct biocatalytic reactors such as the capillaric coil modular reactor. Such biocatalytic reactors were used in a recirculation system for the conversion of substrates. The biocatalytic reactors showed initial decreases of activity to stable limits which are maintained over a large number of reactor volume replacements. The stable limits correspond to approximately 35% of the initial activities for lysozyme and invertase, 25% for urease, 15% for glucose oxidase.The mechanism of complex formation between collagen and enzyme involves multiple salt linkages, hydrogen bonds, and van der Waals interactions. This protein‐protein interaction which leads to stable complexes by both impregnation and electrocodeposition processes is unique among the enzyme immobilization methods currently available.
Effectiveness factor calculations for immobilized enzyme catalysts
Authors: Fink David J. , Na Tsungyen , Schultz Jerome S. 
Published: December 2004

AbstractThe steady state, nonlinear diffusion equations which describe reactions in constrained enzyme solutions are of great interest in many biological and engineering applications. As in other types of nonlinear differential equations, exact analytical solutions do not exist except in some simplified cases. In this paper, a general procedure is presented for solving numerically for the substrate concentration profile and effectiveness factor utilizing the transformation method suggested by Na and Na. Design correlations for enzyme solutions constrained within spherical membranes are included. The use of a unique definition of the Thiele Modulus in these charts permits the clear illustration of the effects of substrate concentration and external mass transfer resistances on the overall effectiveness factor for the catalyst particle.
Lysis ofMicrococcus lysodeikticus by lysozyme covalently immobilized on cellulose and polyacrylamide
Authors: Datta R. , Armiger W. , Ollis D. F. 
Published: December 2004

AbstractLysozyme immobilized on polyacrylamide beads or cellulose fibers is found to retain activity for hydrolysis of the cell walls of Micrococcus lysodeikticus. The immobilization on cellulose is somewhat reversible; the polyacrylamide immobilized lysozyme does not release any enzyme upon washing as evidenced by UV and lytic activity tests. The specific catalytic activity of the lysozyme‐polyacrylamide system is found to decline as the density of derivatized surface groups is increased; a model of protein deactivation due to excess surface coupling is presented as a possible rationale for such specific activity variations.
Starch conversion by soluble and immobilized α‐amylase
Authors: Linko Yu‐Yen , Saarinen P. , Linko M. 
Published: December 2004

AbstractB. subtilis α‐amylase was immobilized on cyanogen bromide activated carboxymethyl cellulose. The conversion of wheat starchwas carried out at 72°C in a stirred tank by soluble and immobilized α‐amylase. The initial reaction rate with immobilized α‐amylase was lower than with the soluble enzyme, but after 1 hr immobilized α‐amylase produced a higher quantity of reducing sugars than the soluble enzyme. The action pattern of immobilized α‐amylase was different from that of the soluble enzyme: immobilized α‐amylase produced relatively more glucose and maltose, except at the beginning of conversion. Immobilized α‐ readily hydrolyze G6. The starch conversion by immobilized α‐amylase was not diffusion controlled at a stirring rate of 100‐300 rpm.
Lactase and other enzymes bound to chitin with glutaraldehyde
Authors: Stanley W. L. , Watters G. G. , Chan B. , Mercer J. M. 
Published: December 2004

AbstractAcid tolerant lactase (I), α‐chymotrypsin (II), and acid phosphatase (III) were immobilized on chitin with glutaraldehyde. Pretreatments of the chit in with acid, alkali, ammonia, and pronase were compared with respect to release of titratable amino groups and ability to retain lactase activity. Shrimp chitin appeared to be more sensitive to pretreatment conditions and so effort was concentrated on crab. An acid‐alkali pretreatment was selected as most practical and economical, and the properties of enzymes fixed on crab chitin were studied intensively. The pH optima of the fixed enzymes were shifted about one pH unit; the shift for I was toward more acid pH, for II was toward alkaline pH, and for III was toward acid pH. The retained activity of immobilized I was approximately 60% that of the native enzyme. A column in continuous operation with I on chitin‐glutaraldehyde gave an apparent activity half‐life of 27 days.
The enzymatic transformation of water‐insoluble reactants in nonaqueous solvents. Conversion of cholesterol to cholest‐4‐ene‐3‐one by a Ncardia sp.
Authors: Buckland B. C. , Dunnill P. , Lilly M. D. 
Published: December 2004

AbstractThe rapid conversion of cholesterol to cholestenone by Nocardia in the presence of high proportions of water‐immiscible solvent has been demonstrated. At high agitator speeds, the reaction rate was not limited by the rates of transfer of oxygen or cholesterol to the microorganisms. Using 100 g of thawed cells in 200 ml of carbon tetrachloride containing 16% (w/v) cholesterol, at 20°C cholestenone was formed at 7 g/hr. Cells could be separated easily from the organic solvent and reused. After 7 runs (69 hr) the reaction rate had fallen only to half the value for the first run.
Continuous hydrolysis of sucrose by invertase adsorbed in a tubular reactor
Authors: Boudrant Joseph , Cheftel Claude 
Published: December 2004

AbstractStudies were made of invertase adsorption on Amberlite ion exchange resins. Up to 4000 units of adsorbed enzymatic activity (aea) were obtainedper g of IRA 93 resin; for an aea of 1600 units, the maximum ratio of aea over units of soluble enzyme used for adsorption was close to 50%. Nodesorption occurred during extensive washing at 30°C with 0.01Msodiumacetate buffer at pH 5. Progressive desorption of aea from the invertase–IRA 93 complex occurred when buffer molarity and temperature were increased. Desorption differed only slightly when the buffer pH was 3 or 5. Theoptimum pH of aea was 3.2 with IRA 93 resin, and varied between 3.2 and 5.1with other resins, depending on their anionic or cationic nature. Batch hydrolysis of sucrose by IRA 93–adsorbed invertase followed 1st order kinetics with respect to the substrate concentration, as in the case of soluble invertase.Continuous sucrose hydrolysis with IRA 93–adsorbed invertase was performed in a tubular reactor, and the percent conversion was experimentally determined as a function of the flow rate. The reaction was experimentally determined 50% (w/v) sucrose solution, at pH4 and 30°C; at the selected flow rate, the ratio of sucrose hydrolysis remained constant and close to 76%. This shows that invertase was not desorbed from the tubular reactor. Some continuous hydrolyses were performed with an industrial sucrose solution: enzymatic activity seemed to be stable for anextended period for time (1 month) at 30°C and pH 3 or 4.
Dynamics of mixed populations having complementary metabolism
Authors: Meyer James S. , Tsuchiya H. M. , Fredrickson A. G. 
Published: December 2004

AbstractThe dynamics of a system of two microbial populations having complementary metabolism are investigated by means of simple mathematical models of growth. Complementary metabolism as used here means that each population produces a substance—not present in the initial or feed medium—required by the other for growth. The simple models indicate that (1) something other than lack of the substrate or growth factor produced by its partner must limit the growth of at least one population and (2) the coexistence steady state of such populations in continuous culture is not stable with respect to large perturbations, though it is stable with respect to a wide range of perturbations.
Engineering analysis of continuous production of L‐aspartic acid by immobilized Escherichia coli cells in fixed beds
Authors: Sato Tadashi , Mori Takao , Tosa Tetsuya , Chibata Ichiro , Furui Masakatsu , Yamashita Kiyokazu , Sumi Akihiko 
Published: December 2004

AbstractThe reaction mechanism and decay behavior of aspartase activity for immobilized Escherichia coli cells were investigated by using a sectional packed column.Reaction within the immobilized cell column proceeded at zero‐order on substrate solutions ranging in concentration from 0.1 to 1.0M, and the initial reaction rate was found to be 1.556 × 10−2 mol/min/liter of immobilized cells.The effect of temperature on the reaction rate constant was investigated. The Arrhenius plot was straight line at temperatures below 43°C, and the activation energy for immobilized cells was calculated to be 12.36 kcal/mol.Asparatase activity in the immobilized cell column decayed exponentially and uniformly in all sections of a column. Its half‐life was approximately 120 days.The rate of formation of L‐aspartic acid was shown to be independent of column dimensions.
Enzyme mechanisms involved in cellulose hydrolysis by the rot fungus Sporotrichum pulverulentum
Authors: Eriksson Karl‐Erik 
Published: December 2004

AbstractThis article presents a review of the enzyme mechanisms involved in degradation of cellulose by the white‐rot fungus Sporotrichum poulverulentum. The hydrolytic enzymes involved include: (1) five endo‐1,4‐β‐glucanases; (2) one exo‐1,4‐β‐glucanase, and (3) one or several 1,4‐β‐glucosidases. A recently discovered oxidative enzyme of importance in in vitro cellulose degradation seems to be a cellobiose oxidase. An oxidoreductase, cellobiose:quinone oxidoreductase, is of importance both in cellulose and in lignin degradation. Regulatory mechanisms of the extracellular enzyme activities, such as monosugar levels causing catabolite repression of the endoglucanases, have also been investigated. The enzymes used by S. pulverulentum in cellulose hydrolysis are compared to those used by Trichoderma viride. Very similar types of enzymes are used in both cases. However, no oxidative enzyme has so far been found to be involved in extracellular cellulose degradation in the case of T. viride. Recommendations for further research are given.
Fungal cellulases as an aid for the saccharification of cassava
Authors: De Menezes Tobias J. B. , Arakaki Tomas , DeLamo Paulo R. , Sales Arlindo M. 
Published: December 2004

AbstractCulture broths of cellulolytic fungi were used together with commercial amylases to enhance the saccharification of cassava starch slurry. It was found that the addition of appropriate concentration of the cellulases Trichoderma viride and a soil isolated Basidiomycete, increased both the rate of sugar formation and the degree of solubilization, and decreased the viscosity of the hydrolyzates. Owing to the improvement of the rheological properties of the must, and the additional sugar produced, an increased ethanol yield would be expected from the alcoholic fermentation of this hydrolyzate.
Effect of thiol reagents on extractability of protein from yeast
Authors: Shetty K. Jayarama , Kinsella John E. 
Published: December 2004

AbstractThe effect of soluble thiol reagents on the extractability of protein from yeast cells was studied. The incubation of yeast cells with dithiothreitol, 2‐mercaptoethanol, or monothioglycerol markedly stimulated the release of soluble carbohydrates into the medium. There was a concomitant improvement (over twofold) in the extractability of protein from the yeast cells. The thiol reagents activated the proteolytic enzymes of the yeast cells. Unless inactivated, these enzymes hydrolyze the extracted protein.
Stabilization of proteolytic enzymes in solution
Authors: Feder Joseph , Kochavi Daniel , Anderson Richard G. , Wildi Bernard S. 
Published: December 2004

AbstractThe stability of the neutral and alkaline proteases in a Bacillus subtilis enzyme mixture was studied in aqueous solutions at room temperature. Stabilization of the proteases in solution for periods up to 25 days was achieved by the addition of various protein preparations including casein and soya protein. The degree of stabilization by casein was concentration dependent to about 2% protein. The instability of the neutral protease in solutions of the B. subtilis enzyme mixture was shown to be due primarily to proteolysis by the alkaline protease since the diisopropylfluorophosphate‐treated enzyme was quite stable. Formulation of such enzyme solutions at low pH gave greater stability as did solutions containing an alkaline protease inhibitor from potatoes. A Conceptual approach to the formulation of enzyme solutions containing proteolytic enzyme to ensure maximum stability is proposed.