摘要:

AbstractPrevious theories of nutrient supply to microbial floes assumed that transport within the flocs was by molecular diffusion, and they predict that overall nutrient uptake is reduced in floes compared to dispersed cells. Calculations, supported by recent advances in understanding fluid flow through suspended aggregates, however, have shown that substantial fluid flow may occur through highly permeable bacterial floes. Since bioflocculation of microorganisms in bioreactors is known to occur under conditions of low substrate availability, the rate of substrate uptake is assumed to be mass transfer limited. The hydrodynamic environment of a cell then determines cellular uptake rates. Through development of a relative uptake factor, the overall uptake by cells in flocs in sheared fluids and floes attached to bubbles are compared with the uptake by an identical quantity of dispersed cells. Bioflocculation is found to increase the rate of substrate transport to cells in permeable floes compared to dispersed cells, particularly for large‐molecular‐weight substrates and when bubbles are pres

ISSN:0006-3592    

DOI:10.1002/bit.260310202

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

年代:1988

数据来源: WILEY

摘要:

AbstractA three‐pool growth model of an individualEscherichia colicell is described herein. The model is based on a previously developed chemically structured complex single cell growth model. The reduction in model complexity and the identification of the essential modes of motion, over the time scale of growth, is achieved by temporal decomposition and analysis of hierarchy in relaxation times. The three‐pool model faithfully simulates the changes in cell size, cell shape, cell macromolecular composition, DNA initiation and termination periods, and the dependence of cell growth under abiotic glucose limitation. The predictions made by the reduced model compare favorably with both the experimental data and those of the full single cell model (SCM) without any parameter adjustments. The three‐pool model has very few significant parameters and has the potential to find immediate practical use in bioreactor design and process control strategies. The model development illustrates the use ofmodalanalysis to yield reduced physiologically realistic dynamic model of complex microbial system such asE.

ISSN:0006-3592    

DOI:10.1002/bit.260310203

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

年代:1988

数据来源: WILEY

摘要:

AbstractA model for the tryptophan operon is formulated based on the genetic and biophysical data available on the structure of the operon and the nature of interactions between the represser and its ligands. Studies have been done, on wild‐type, superrepressing, and loose‐binding strains to identify conditions at which the stability of the system changes (i.e., evolves to a stable synthesis or periodic synthesis with increasing amplitude). Also, the factors that increase the yield of tryptophan are studied and predictions made, based on the results, for obtaining overproducing strains of tryptophan that can be used for the industrial production of this useful amino a

ISSN:0006-3592    

DOI:10.1002/bit.260310204

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe regulation and kinetics of formation of an inducible, cell‐bound oxacillin‐hydrolyzing β‐lactamase (M‐OXA) by a methanol‐grownPseudomonasstrain were investigated in batch, chemostat, and two‐stage continuous cultures. The extent to which enzyme production occurs declines at increased growth rates, and the rate of M‐OXA β‐lactamase production follows a kinetic pattern that is partially growth independent and partially inversely growth linked. Growth and enzyme formation are regulated differently by medium constituents. The initial steps of M‐OXA β‐lactamase synthesis takes place during the exponential growth phase, and active enzyme is produced by induced nonproliferating cells, probably throug

ISSN:0006-3592    

DOI:10.1002/bit.260310205

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

年代:1988

数据来源: WILEY

摘要:

AbstractThis work has studied the effect of pH on specific growth rate μ, yield factorY, and specific substrate consumption rateUfor two mixed microbial populations (sludge A and B) in a batch reactor with a limiting substrate (phenol). The mathematical analysis of μ andUas a function of pH has been applied not only to the results of the present work but also to other published data. On the basis of the results obtained, the following remarks can be made: (a) The effect of pH on bacterial activity differed for the two sludges; (b) variations in pH of one unit more or less than optimum pH can give rise to appreciable variations in μ andU;and (c) with regard to the mixed populations used in this study, the μ orUand pH data for the range investigated can be suitably described by a parabolic relat

ISSN:0006-3592    

DOI:10.1002/bit.260310206

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe productivity of the acetone–butanol fermentation was increased by continuously removing acetone and butanol from the fermentation broth during fed‐batch culture. Whole broth containing viable cells ofClostridium acetobutylicumwas cycled to a Karr reciprocating plate extraction column in which acetone and butanol were extracted into oleyl alcohol flowing counter‐currently through the column. By continuously removing these toxic metabolites from the broth, end product inhibition was reduced, and a concentrated feed solution containing 300 g/L glucose was fermented at an overall butanol productivity of 1.0 g/L h, 70% higher than the productivity of normal batch fermentation. The continuous extraction process provides flexible operation and lends itself to process sca

ISSN:0006-3592    

DOI:10.1002/bit.260310207

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

年代:1988

数据来源: WILEY

摘要:

AbstractAn unstructured mathematical model is proposed for mixed culture growth of two different bacterial species that exhibit “opposite” substrate preferences in response to the “same” environmental conditions. The model incorporates enzymatic control mechanisms such as induction, repression, and inhibition in the microorganisms as manifested in their preferential utilization of substrates and microbial interactions such as amensalism and competition. The model predicts cell mass, substrate concentrations, dissolved oxygen tension, as well as key enzyme levels. The predictions of the model are compared with experimental data for pure culture growth and for mixed culture growth on two substrates, glucose and citrate, in a batch

ISSN:0006-3592    

DOI:10.1002/bit.260310208

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

年代:1988

数据来源: WILEY

摘要:

AbstractSix endoglucanases (Endo I, II, III, IV, V, and VI), three exoglucanases (Exo I, II, and III), and a β‐glucosidase (β‐gluc I) isolated from a commercial cellulase preparation ofTrichoderma virideorigin were examined as to their activities on xylan ex oat spelts. Endo I, II, and III as well as Exo II and III showed no activity toward xylan and were classified as specific glucanases. Less specificity was found for the endoglucanases Endo IV, V, and VI, Exo I, and β‐gluc I, whose enzymes were able to hydrolyze xylan. With respect to product formation these xylanolytic cellulases fit the classification of xylanases generally accepted in the literature. Kinetic experiment with xylan, CM‐cellulose, andp‐nitrophenyl‐β‐D‐glucoside revealed that Endo IV, V, an VI and Exo I prefer to hydrolyze β‐1, 4‐D‐glucosidic linkages. β‐Gluc I showed

ISSN:0006-3592    

DOI:10.1002/bit.260310209

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

年代:1988

数据来源: WILEY

摘要:

AbstractMouse–human hybridoma 4H11 cells producing anti‐Pseudomonassp. monoclonal antibody (IgA) grew in a serum‐free medium supplemented with insulin, transferrin, ethanolamine, and selenite (ITES). The hybridoma could be applied to high‐density culture in a serum‐free medium supplemented with ITES, 0.5% BSA, egg yolk VLDL, and artificial blood FC‐43 in a culture vessel equipped with hollow‐fiber modules for medium exchange. Total cell density reached 1.1 × 107cells/mL (viable cell density was 7.6 × 106cells/mL), and the IgA productivity was around 20 μg/106cells/day in the serum‐free medium, which corresponded to the levels in serum

ISSN:0006-3592    

DOI:10.1002/bit.260310210

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

年代:1988

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260310211

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

年代:1988

数据来源: WILEY