摘要:

AbstractMicrobial souring (H2S production) in porous media was investigated in an anaerobic upflow porous media reactor at 60°C using microbial consortia obtained from oil reservoirs. Multiple carbon sources (formate, acetate, propionate, iso‐ andn‐butyrates) found in reservoir waters as well as sulfate as the electron acceptor was used. Kinetics and rates of souring in the reactor system were analyzed. Higher volumetric substrate consumption rates (organic acids and sulfate) and a higher volumetric H2S production rate were found at the from part of the reactor column after H2S production had stabilized. Concentration gradients for the substrates (organic acids and sulfate) and H2S were generated along the column. Biomass accumulation throughout the entire column was observed. The average specific sulfate reduction rate (H2S production rate) in the present reactor after H2S production had stabilized was calculated to be 11062 ±2.22 mg sulfate‐S/day g biomass. © 1994 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260440302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractStreptokinase (SK) recovery from streptococcal fermentation broth by cross‐flow microfiltration has been studied. Recovery of SK in the filtrate, independent of the volumetric concentration factor, is approximately two‐fold lower than the initial SK activity in the fermentation broth; moreover, the SK activity in the retentate increase during the process, reaching a concentration factor of 2.73. These results show that the membrane works more as an ultrafiltration membrane, with rejection of S = 0.6, than as a microfiltration membrane. Under filtration conditions, the membrane permeation rate decreased with time. This decreased could be explained by deposition and interaction of material onto/with the membrane resulting in the concentration of permeable products. Studies of the individual concentration factors for the main streptococcal exocellular proteins, indicate clearly that the concentration of the proteins during the microfiltration process is independent of the size of the proteins, suggesting that other factors, such as charge and hydrophobicity, along with concentration‐polarization, should be taken also into account for the understanding of this phenomenon. © 1994 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260440303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of pH and temperature on the thermal denaturation of micrococcal nuclease wer4e investigated. The ranges employed were between pH3.30 and pH9.70 and between 10°C and 85°C, respectively. The reversible denaturation involved in the whole process was clearly discriminated from the irreversible one. The former took place with a large enthalpy change of 384 kJ mol−1at pH 9.70, where the enzyme exhibited it s maximum activity. The latter probably led to aggregation because the successive long incubation after complete deactivation caused precipitation. A reasonable scheme explaining the process involving both denaturations was proposed and the kinetic on the irreversible deactivation was performed. It was revealed that the irreversible deactivation involved two types of reactions whose activation energies were relatively small: 22.2 kJ mol−1and 18.8kJ mol−1. The presence of sucrose suppressed the reversible denaturation without significant influence on enthalpy change, whereas it affected little the irreversible deactivation kinetically. The effects of pH change and addition of sucrose on the denaturation were discussed thermodynamically, especially in terms of the entropy change. © 1994 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260440304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAdenosine 3′:5′ cyclic monophosphate seems to regulate antibiotic biosynthesis and secondary metabolism in tylosin‐producing cultures ofStreptomyces fradiaeC373.1. A dose‐dependent response is observed by exogenous additions of dibutyryl cyclic AMP (cAMP), and is related to the nutritional status of the culture. Addition of cAMP to cultures growing in nutritionally lean media caused higher cumulative antibiotic tigers and some cellular differentiation compared with the control. In nutritionally rich media, a qualitatively different behavior resulted: an almost instantaneous shift toward secondary metabolism occurred. The response is characterized by extensive cellular differentiation with little growth and only a trace of antibiotic production. The possible role of cyclic AMP n the regulation of tylosin biosynthesis and secondary metabolism and its relation to specific nutrient limitations in synthetic, defined media inStreptomyces fradiaeis discussed. © 1994 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260440305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTransition time of metabolic systems in introduced as a suitable optimization criterion for biotechnological processes in which it is desirable to reduce the lag time and minimize the mass contained within the system. Lag time is the time needed for the system to attain the steady state. Results obtained from the sensitivity analysis of this steady state response are presented within the metabolic control analysis and applied to 3 case studies. In all of them the information provided by the transition time control profile allows the implementation of a strategy for biotechnological manipulations aimed at the improvement of the process. © 1994 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260440306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIsolated cell walls of the yeastSaccharomyces cerevisiaewere treated by either chemical (alkali and acid) or enzymatic (protease, mannanase or β‐glucuronidase) processes to yield partially purified products. These products were partially characterized by infrared analysis. They were subsequently reacted with heavy metal cation solutions and the quantity of metal accumulated by the cell wall material determined. The Cu2+ion (0.24, 0.36, 1.12, and 0.60 μmol/mg) was accumulated to a greater extent than either Co2+(0.13, 0.32, 0.43, and 0.32 μmol/mg) or Cd2+(0.17, 0.34, 0.39, and 0.32 μmol/mg) by yeast cell walls, glucan, mannan, and chitin, respectively The isolated components each accumulated greater quantities of the cations than the intact cell wall. Removal of the protein component of the yeast cell walls by Pronase caused a 29.5% decrease in metal accumulation by yeast cell walls per mass, indicating the protein is a heavy metal accumulating component. The data indicate that the outer mannan–protein layer of the yeast cell wall is more important than the inner glucan‐chitin layer in heavy metal action accumulation. © 1994 John Wiley

ISSN:0006-3592    

DOI:10.1002/bit.260440307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of step‐change increase in the concentrations of amino acids and vitamins on the metabolism, growth, and antibody productivity of a murine hybridoma cell line grown in continuous culture on serum‐free medium are presented. Additions of the amino acids cysteine with methionine, tryptophan, and isoleucine with valine and vitamin B12(as cyanocobalamin) resulted in significant increases in viable cell concentrations. Additions of aspartate with asparagine, and threonine with vitamin B1(as thiamine hydrochloride) resulted in significant increases in final antibody concentrations. Substantial decrease in the fraction of amino acid nitrogen excreted as ammonia occurred upon supplementation with three times the normal concentrations of branched chain amino acids. Decreases in the fraction of amino acid nitrogen converted to ammonia were paralleled by increases in the fraction converted to alanine. © 1994 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260440308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractDuring a 70‐h fermentation of a lignocellulose hydrolysate, the ethanol produced was monitored on‐line using a microdialysis probe as an in situ sampling device. The dialysate components were then separated in a column liquid chromatographic system and the ethanol was selectively detected by an amperometric alcohol biosensor. The result was compared with two off‐line analysis methods: one chromatographic method with refractive index (RI) detection and one enzymatic method based on spectrophotometric detection. The two methods base on enzymes were shown to give lower values than the chromatographic method based on RI detection, which is discussed n terms of selectivity. The investigated on‐line setup was found to be a flexible system for monitoring of fermentations, allowing a sampling frequency of at least 12 h−1and with a delay between sampling and detection of less than 5 min. © 1994 John Wiley

ISSN:0006-3592    

DOI:10.1002/bit.260440309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractBiofilm formation and plasmid segregational instability in biofilm cultures ofEscherichia coli DH5α(pMJR1750) were investigated under different medium‐carbon‐to‐nitrogen (C/N) ratios. At C/N ratios of 0.07 and 1, net accumulation of both biofilm plasmid‐bearing and plasmid‐free cells continued through the entire experiment without attaining any apparent steady state. At C/N ratios of 5 and 10, net biofilm cell accumulation for the two populations reached apparent steady states after 84 and 72 h, respectively. At C/N ratios of 0.07 and 1, polysaccharide production increased slowly and reached about 2g alginate equivalent/cm2by the end of both experiments. At a C/N ratio of 5, polysaccharide increase significantly after 84 h, reaching about 7μg alginate equivalent/cm2prior to termination. At a C/N ratio of 10, polysaccharide increased significantly after 72 h and reached 21 μg alginate equivalent/cm2at 108 h. At C/N ratios of 0.07 and 1, protein production reached 6.5 and 4 μg/cm2, respectively. At C/N ratios of 5 and 10, protein production increased slightly for the first 84 h and reached a maximum at 108 h, at 3 and 2 μg/cm2, respectively, then decreased over the last 12 h of the experiment. Ratios of polysaccharide to protein increased with increasing C/N ratios. At C/N ratios of 0.07 and 1, the ratios between extracellular polysaccharide (EP) and protein were no more than 205 μg polysaccharide/μg protein, whereas those at C/N ratios of 5 and 10 increased to about 7 and 12 μg polysaccharide/μg protein, respectively.Probabilities of plasmid loss in the biofilm cultures increased with increasing C/N ratios. At C/N ratios of 0.07, 1, and 5, the probabilities of plasmid loss were 0.0013 ± 0.011, 0.020 ± 0.006 and 0.122 ± 0.021, respectively. At a C/N ratio of 10, the probability of plasmid loss was significantly higher, reaching 0.38 ± 0.125. The increase of probability of plasmid loss at higher C/N ratios results from competition between cell replication and extracellular polysaccharide production. © 19

ISSN:0006-3592    

DOI:10.1002/bit.260440310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA proteinase isolated fromThermusRT41a was immobilized to controlled pore glass beads and was used in the free and immobilized forms for peptide synthesis. The observed maximum yield was the same in both cases. a number of dipeptides were produced from amino acid esters and amides. The best acyl components, from those tested, were found to be Ac‐Phe‐OEt and Bz‐Ala‐OMe. Tur‐NH2, Trp‐NH2, Leu‐pNA, and Val‐pNA were all reactive nucleophiles.The kinetically controlled synthesis of Bz‐ala‐Tyr‐NH2was optimized by studying the effect of pH, temperature, solvent concentration, ionic strength, and nucleophile and acyl donor concentration, ionic strength, and nucleophile and acyl donor concentration on the maximum yield. The initial conditions used were 25 mMBz–ala‐OMe, 25 mMTyr‐NH2, 70°C, pH 8.0, and 10% v/v dimethylformamide (DMF). The optimum conditions were 90% v/v DMF using 80 mMbz‐Ala‐OMe and 615 mMTyr‐NH2at 40°C and pH 10. These conditions increased the maximum conversion from 0.75% to 26% (of the original ester concentration). In a number of other cosolvents, the best peptide yields were observed with acetonitrile and ethyl acetate. In 90% acetonitrile similar yields were observed to those in 90% DMF under optimized conditions except that the acyl donor and nucleophile concentrations could be reduced to 25 mMand 100mM, respectively. The effect of the blocking group on the nucleophile was also investigated; ‐βNA and ‐pNA as blocking groups improved the yields markedly. The blocking and leaving groups of the acyldonor had no effect on the dipe

ISSN:0006-3592    

DOI:10.1002/bit.260440311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY