摘要:

AbstractPlasmid loss kinetics forSaccharomyces cerevisiaetransformed with the 2‐μm DNA‐based‐plasmid pUCKm8 were measured in nonselective and selective media. The plasmid pUCKm8 gives the organism two new phenotypes: resistance to the wide spectrum antibiotic G418 sulfate, and the ability to produce the enzyme, β‐lactamase. Plasmid stability was determined using the production of β‐lactamase as a marker. The effect of G418 on the growth rates of all organisms present in the culture and on plasmid stability was also determined. Mathematical models describing plasmid loss kinetics during exponential growth for both nonselective and selective conditions are used to simulate the experimental data. In nonselective medium, over 80% of the cells still exhibited the desired phenotype after 50 doublings. In medium containing G418, improvements in plasmid stability were only marginal due to the appearance of antibiotic‐r

ISSN:0006-3592    

DOI:10.1002/bit.260320602

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

年代:1988

数据来源: WILEY

摘要:

AbstractWhenEscherichia colicontaining the plasmid ptac11 is induced with 10−4Misopropyl‐β‐thiogalactopyranoside (IPTG), 90% of the β‐lactamase activity of an overnight culture is present in the medium. The high extracellular activity of β‐lactamase does not result from cell lysis but from an increase in the permeability of the outer membrane. The excreting cells release several other periplasmic enzymes into the extracellular fluid and are more sensitive to lysis by detergents. It was also shown that in these cells the level of two membrane proteins, OmpA and OmpC, is decreased. None of these phenomena were observed with the plasmid pDW17, which has a mutation in thetacpromoter that reduces its activity to one fourth of th

ISSN:0006-3592    

DOI:10.1002/bit.260320603

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe anaerobic digestion of a cellulose‐enriched fraction of domestic refuse by means of rumen microorganisms in an “artificial rumen” digester was studied. Various combinations of solid and liquid retention times and loading rates were applied to establish optimum conditions for the acidogenic phase digestion of the refuse fraction. An optimal substrate conversion of about 72% was obtained at a loading rate of 23.4 g volatile solids (VS)/L d and a solids retention time of 90 h. Variation of dilution rate between 1.04 and 3.14 fermentor volume turnovers per day had no effect on degradation efficiency. At a loading rate of 23.4 g VS/L d a differential removal rate of solids and liquids appeared to be necessary to obtain an effective degradation of the refuse fra

ISSN:0006-3592    

DOI:10.1002/bit.260320604

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

年代:1988

数据来源: WILEY

摘要:

AbstractCalcium alginate gel stabilized with a polyelectrolyte complex (PEC) consisting of potassium poly(vinyl alcohol) sulfate (KPVS) and trimethylammonium glycol chitosan iodide (TGCI) was used for the immobilization of β‐amylase. The immobilization was made by gelling aqueous droplets of enzyme solution including both sodium alginate and KPVS in a CaCl2solution containing TGCI. The activity of the enzyme entrapped into the stabilized gel beads was evaluated by studying the batch reaction kinetics of enzyme‐catalyzed hydrolysis of maltotetraose. Repeated kinetic measurements, totaling 18, were carried out at fixed time intervals. After each measurement the beads were stirred for 1 day in a freshly prepared 10 mMNaCl solution at 3°C. It was found that the immobilized system remained stable without leading to a serious loss of the activity or to a large leakage of the enzyme from the support. This was explained as being due to a PEC‐crosslinked contracted network structure of the stabilized gel

ISSN:0006-3592    

DOI:10.1002/bit.260320605

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

年代:1988

数据来源: WILEY

摘要:

AbstractCellulase producing activity ofTrichoderma reeseiQM9414 was examined under various agitation intensities and at the dissolved oxygen concentration above 3 ppm. The producing activity greatly depended upon the agitation intensity, and the dependence on the agitation was different for each cellulase‐constituting component. The maximum producing activities of FPA, CM Case, and β‐glucosidase were obtained under different agitation conditions, 1.0, 0.7, and 1.4 m/s in tip velocity, respectively. Intensive agitation brought about remarkable reduction in all cellulase components. The mycelial transformation through agitation intensity was also observed. Comparatively mild agitation of 0.3–1.0 m/s caused pellet formation as the culture progressed, although the pelletization was delayed with increasing agitation intensity. The behavior of the pelletization did not occur at 1.3 and 1.7 m/s throughout the course of cultivation, and under the latter agitation condition hyphae were broken up into short fragments. The cellulase producing activity is discussed in relation to such morphological c

ISSN:0006-3592    

DOI:10.1002/bit.260320606

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe interactions between chloroplast membranes and their microenvironment within artificial matrices (albumin‐glutaraldehyde matrix, polyurethane foam) where investigated. Particularly, the influence of a high‐ionic‐strength medium (0.75Mpotassium citrate) on the stability of the photosynthetic ferricyanide reduction by immobilized thylakoids has been studied. A method of data analysis based on a nonlinear identification method combined with the numerical integration of the equation of the transient state of the continuous stirred tank reactor (CSTR) is proposed to estimate the actual degradation of the photosynthetic electron transfer. A statistical analysis achieved on the parameter values has allowed a quantitative assessment of the global behavior of immobilized chloroplast membranes. From the mathernatical analysis of the experimental data, we demonstrate that citrate used in the reaction media prevents the photoinactivation of the electron transfer chain whatever the nature of the matrix or the type of the reactor. The use of an albumin‐glutaraldehyde matrix or an open reactor during experiments also has allowed a better stabilization of the photosystems under operational con

ISSN:0006-3592    

DOI:10.1002/bit.260320607

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

年代:1988

数据来源: WILEY

摘要:

AbstractAutohydrolysis and ethanol‐alkali pulping were used as pretreatment methods of wheat straw for its subsequent saccharification byTrichoderma reeseicellulase. The basic hydrolysis parameters, i.e., reaction time, pH, temperature, and enzyme and substrate concentration, were optimized to maximize sugar yields from ethanol‐alkali modified straw. Thus, a 93% conversion of 2.5% straw material to sugar syrup containing 73% glucose was reached in 48 h using 40 filter paper units/g hydrolyzed substrate. The pretreated wheat straw was then fermented to ethanol at 43°C in the simultaneous saccharification and fermentation (SSF) process usingT. reeseicellulase andKluyveromyces fragiliscells. From 10% (w/v) of chemically treated straw (dry matter), 2.4% (w/v) ethanol was obtained after 48 h. When theT. reeseicellulase system was supplemented with β‐glucosidase fromAspergillus niger, the ethanol yield in the SSF process increased to 3% (w/v) and the reaction time was shortened

ISSN:0006-3592    

DOI:10.1002/bit.260320608

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

年代:1988

数据来源: WILEY

摘要:

AbstractLysozyme was recovered from egg white by continuous precipitation with polyacrylic acid (molecular weight of 4 × 106). Precipitator residence time and shear rate had significant effects on the size distribution of the precipitate, but no clear effects on the compositions. Precipitate mean size increased with higher shear, indicating growth phenomena predominating over breakage. Also, an enhancement of growth rate at small sizes was noted. The Camp number successfully characterized the interaction of shear rate and residence time on the particle size

ISSN:0006-3592    

DOI:10.1002/bit.260320609

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

年代:1988

数据来源: WILEY

摘要:

AbstractA population‐balance model has been used to characterize continuous polyelectrolyte precipitation of egg white proteins. We have modeled the particle size distributions of aggregates formed under a range of mixing conditions. The models, accounting for aggregate growth (by both shear‐driven and Brownian‐like collisions), breakage (by hydrodynamic shear or aggregate‐aggregate collisions), and birth (by the breakage of large aggregates), fit the data well. The kinetic constants show dependencies on shear rate and residence time that have not been previously theoretically predicted; these dependencies are due in part to aging effects on the aggregate. The model constants show a dominance of growth over breakage, supporting qualitative interpretations of the particle size distributions. A mechanism for growth‐rate enhancement, caused by polymer extensions from the particle surfaces, produced improved model performance. A collisional breakage mechanism is

ISSN:0006-3592    

DOI:10.1002/bit.260320610

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

年代:1988

数据来源: WILEY

摘要:

AbstractFermentation kinetics ofClostridium formicoaceticumgrown on lactate at pH 7.0 and 35°C was studied. Acetate was the only fermentation product and its production was growth associated. The growth of this bacterium was insensitive to the lactate concentrations studied, but was inhibited by acetic acid. A Monod‐type expression with product inhibition similar to the noncompetitive inhibition of enzyme kinetics was used to model the batch fermentation. An integrated equation was developed and used to help estimating the kinetic parameters in the model. This mathematical model can be used to simulate the homoacetic fermentation of lactate byC. formicoaceticumat pH 7.0 and 35

ISSN:0006-3592    

DOI:10.1002/bit.260320611

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

年代:1988

数据来源: WILEY