摘要:

AbstractThe cybernetic framework developed by Ramkrishna and co‐workers is shown to encompass the regulation of nutrient transport processes as well as the effect of nutrient transport on the biotic phase. A structured model which accounts for both an abiotic or environmental phase and a biotic or cellular phase is proposed to describe bacterial growth on lactose as the limiting carbon and energy source. In the presence of lactose, competing uptake mechanisms are proposed. At low lactose concentrations, an energy‐requiring transport process is the preferred uptake mechanism. The coupling between cellular energetics and nutrient uptake results in an interesting intermittent growth phenomenon. As the concentration of lactose increases, a nonenergetic transport process is preferred and cellular growth ceases to be intermittent. Model simulations are compared with previously reported experimental results and exhibit good agreement over the entire range of initial lactose concentrati

ISSN:0006-3592    

DOI:10.1002/bit.260371002

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

年代:1991

数据来源: WILEY

摘要:

AbstractSaccharomyces cerevisiaewas cultivated in a 4‐m3pilot plant airlift tower loop reactor with a draft tube in batch and continuous operations and for comparison in a laboratory airlift tower loop reactor of 0.08 m3volume. The reactors were characterized during and after the cultivation by measuring the distributions of the residence times of the gas phase with pseudostochastic tracer signals and mass spectrometer and by evaluating the mixing in the liquid phase with a pulse‐shaped volatile tracer signal and mass spectrometer as a detector. The mean residence times and the intensities of the axial mixing in the riser and downcomer, the circulation times of the gas phase, and the fraction of the recirculated gas phase were evaluated and compa

ISSN:0006-3592    

DOI:10.1002/bit.260371003

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

年代:1991

数据来源: WILEY

摘要:

AbstractWith the aim of possibly extending plant microbiology and photosynthesis beyond the usual applicability in aqueous solution, we investigated the solubilization of plant cells inorganic media with the help of water‐in‐oil microemulsions. Cells isolated from leaves ofRumex obtusifoliuswere solubilized in a water/2‐ethyl‐hexyl‐sodiumsulfosuccinate/isooctane system, containing 20% water (v:v) and 240 mMsurfactant, and the oxygen evolution/consumption was measured polarographically. Although no oxygen evolution was detectable in the organic medium, the cells were able to carry out photosynthetic oxygen consumption at the expense of ascorbate. To a lesser extent, photosynthetic oxygen consumption was measured usingN,N,N′,N′‐tetramethyl‐p‐phenylenediamine as electron donor. The rate of ascorbate photooxidation was linearly related to the con

ISSN:0006-3592    

DOI:10.1002/bit.260371004

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe transient response method was utilized to evaluate the rate constants of reaction over immobilized enzyme. Glucose oxidation catalyzed by the immobilized glucose oxidase in a fixed‐bed reactor was selected as an example. A theoretical model including the effects of axial dispersion, film diffusion, and intraparticle diffusion was established for the reactor. The individual rate constant of each elementary step of this enzymatic reaction was determined through direct fitting of the experimental response data to the mode

ISSN:0006-3592    

DOI:10.1002/bit.260371005

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

年代:1991

数据来源: WILEY

摘要:

AbstractRecombinant plasmid pCEDS is structurally unstable inBacillus subtiliscultures. We have previously shown that stability can be independently increased by changing from a complex medium supporting high growth rates to a chemically‐defined medium supporting a lower growth rate and removal of a 4.77‐kb EcoRI fragment from pCED3 to give plasmid YS1. Further stabilization was achieved by combining the two approaches. In the present work, we show that the stabilization of the plasmid‐encoded LacZ+phenotype can be explained solely by the effect on the growth rate ratio between cells containing modified and parental plasmids. By using modified stability experiments (where a single cell rather than a suspended colony was used to initiate growth), independent growth rate measurements, and a simple mathematical model, we can describe the kinetics of the loss of the LacZ+phenotype in terms of two variables, α andp(where α is the ratio of growth rates between modified and parental cells, andpis the probability of obtaining modified cells from parental cells). Under the conditions tested, the average values of α were 1.52 for cultures growing in complex medium, 1.28 for cultures growing in defined medium, and 1.18 for cultures containing the modified plasmid pYS1 growing in complex medium. The calculatedpvalues ranged between 10−8and 10−10under all conditions. Plasmid (pYS137) was used to directly estimate plasmid deletion rates inB. subtilisand it showed a rate between 5 × 10−8and 1.1 × 10−9deletions/cell/generation. In contrast toB. subtilis, there were no detectable differences in growth rates betweenEscherichia colistrains harboring plasmid pCEDS and plasmid‐free cells. These results explain the observed stability of pCEDS inE. colicultures and indicate that readily detected instability inB. subtiliscultures can be the result of

ISSN:0006-3592    

DOI:10.1002/bit.260371006

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe marine phytoplankterTetraselmis suecicawas grown in shallow outdoor flumes for a period of approximately 6 months at the Natural Energy Laboratory of Hawaii. In full sunlight, gross production rates were 15–20 g C m−2d−1. The corresponding photosynthetic efficiencies (PE's) were 9–10%. Respiration losses removed about half the gross production. The CO2utilization efficiencies of 96 ± 11% were achieved by bubbling CO2into the culture with the use of a counterflow sump system. Adding the CO2in the form of carbonated water resulted in utilization efficiencies of 81 ± 11%. Archimedes screws proved superior to both paddle wheels and propellers as a means of circulating the water in the flumes. Insertion of foil arrays into the flumes to effect systematic mixing of the culture significantly enhanced production. The enhancement was greater when the foils were oriented at a small angle relative to the horizontal than when they were oriented at the same angle relative to the vertical. Light modulation effects are implicated as the probable cause of most of the enhancement. Substitution of electric power plant stack gases for pure CO2resulted in no significant change in the production ofT. suecicagrown in chemosta

ISSN:0006-3592    

DOI:10.1002/bit.260371007

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

年代:1991

数据来源: WILEY

摘要:

AbstractLignocelluloses (steamed hardwood and hardwood kraft pulp) were semicontinuously hydrolyzed on a large scale [2‐2. 5 kg of substrate vs. 20, 000 IU filter paperase (FPase)] using a 10‐L hydrolysis reactor with an ultrafiltration unit for the recovery and reuse of cellulases. The substrate was added to the reactor at appropriate intervals to keep a concentration of approximately 5% (w/v). All of the enzyme was added at the beginning and no further addition was done. The ultrafiltration unit was operated intermittently rather than continuously due to its enough capacity (dilution rate of 2.5 h−1) and making the enzyme durable. The enzyme required to produce one gram of reducing sugar in this reactor was 27.3 FPase IU/g RS for steamed hardwood and 7.4 FPase IU/g RS for hardwood kraft pulp. The sugar composition of hydrolyzate was unaltered virtually from beginning to end of the hydrolysis in spite of the progressive loss of enzyme activities. The analysis of the enzyme composition in the hydrolyzate during hydrolysis revealed that an exo‐β‐D‐glucanase component was adsorbed selectively at the stages of advanced hydro

ISSN:0006-3592    

DOI:10.1002/bit.260371008

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe flotation ofStreptomyces pilosuswas studied in the absence and presence of adsorbed Pb(II) ions on the cell walls and with and without using sodium dodecylsulfate (SDS) as collector. Adsorption of SDS onto the organism in the absence and presence of Pb(II) ions was also investigated. It was found that in the absence of adsorbed Pb(II), very little flotation took place with or without the presence of SDS although SDS adsorbed to some extent on the organism. The presence of Pb(II) on the bacterium's cell walls significantly increased flotation even in the absence of the collector. Addition of SDS, however, further increased both flotation rate and recovery.

ISSN:0006-3592    

DOI:10.1002/bit.260371009

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe oxygen transfer in bioreactors with slurries having a yield stress was investigated. The volumetric mass transfer coefficients in a 40‐L bubble column with simulated fermentation broths, the Theological properties of which were represented by the Casson model, were measured. Experimental data were compared with a theoretical correlation developed on the basis of a combination of Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence. Comparisons between the proposed correlation and data for the simulated broths show good agreement. The mass transfer data for actual mycelial fermentation broths reported previously by the authors were re‐examined. Their Theological data was correlated by the Bingham plastic model. The oxygen transfer rate data in the mycelial fermentation broths fit the predictions of the proposed theoretical correlat

ISSN:0006-3592    

DOI:10.1002/bit.260371010

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe effects of various concentrations of a water‐miscible organic solvent [a 7:3 (v/v) mixture ofN,Ndimethylformamide and dimethylsulfoxide] on the kinetics of papain have been investigated. The parameterskcatandKmfor the amidase and esterase activity of papain usingN‐α‐benzoyl‐DL‐arginine‐p‐nitroanilide (BAPNA) andN‐α‐benzoyl‐L‐arginine ethyl ester (BAEE) as substrates were determined. For both types of activity,kcatinitially increased (up to about 15% solvent), and then decreased with increasing concentrations of organic solvent. In contrast,Kmincreased sharply with the organic solvent concentration. Active site titration at 0 and 50% solvent indicated no change in the amount of active enzyme. Fluorometric measurements of the emission spectrum of papain did not indicate any major conformational changes with increasing concentrat

ISSN:0006-3592    

DOI:10.1002/bit.260371011

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

年代:1991

数据来源: WILEY