摘要:

AbstractA kinetic model for anaerobic digestion of insoluble solid‐state substrates was developed. Rate equations for cell growth and substrate consumption were derived based on the assumption that the microorganisms assimilate the substrate mainly at the point of contact where they grow. The model emphasizes effects of substrate particle size, organic loading, and cell concentration on the rates of cell growth and substrate utilization. Batch digestion of a stearic acid emulsion with a mean particle size of 2.0 μm and a biological sludge was conducted at 30 and 37°C to verify the proposed model. Agreement between the experimental and calculated results indicated the validity of the model for describing the microbial degradation of insoluble solid‐state substrates. Further examinationof the model revealed that with low cell substrate affinity or at low cell concentration, it coincided with a Michaelis–Menten type kinetics in which the effect of particle size was taken into consid

ISSN:0006-3592    

DOI:10.1002/bit.260350602

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe method of resting cells has been of interest in the development of biocatalysts applied to organic reactions.This article deals with the use of resting cells of a thermophilic archaebacteriumSulfolobus solfataricus, in the asymmetric reduction of acyclic, cyclic, and aromatic ketones. The system allows the continuous regeneration of endogenous coenzyme with the coupled substrate approach. The results indicate that the direction of hydride attack was equatorial on thereface of the carbonyl group of substrates producing (S)‐alcohols with a good optical yield. A convenient system for the reuse of resting cells has been set out to synthesize (S)‐alcohols on a preparative sc

ISSN:0006-3592    

DOI:10.1002/bit.260350603

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

年代:1990

数据来源: WILEY

摘要:

AbstractEfficient expression of a foreign protein product by the yeastSaccharomyces cerevisiaerequires a stable recombinant vector present at a high number of copies per cell. A conditional centromere yeast plasmid was constructed which can be amplified to high copy number by a process of unequal partitioning at cell division, followed by selection for increased copy number. However, in the absence of selection pressure for plasmid amplification, copy number rapidly drops from 25 plasmids/cell to 6 plasmids/cell in less than 10 generations of growth. Copy number subsequently decreases from 6 plasmids/cell to 2 plasmids/cell over a span of 50 generations. A combination of flow cytometric measurement of copy number distributions and segregated mathematical modeling were applied to test the predictions of a conceptual model of conditional centromereplasmid propagation. Measured distributions of plasmid content displayed a significant subpopulation of cells with a copy number of 4–6, evenin a population whose mean copy number was 13.5. This type of copy number distribution was reproduced by a mathematical model which assumes that amaximum of 4‐6 centromere plasmids per cell can be stably partitionedat cell division. The model also reproduces the observed biphasic kinetics of plasmid number instability. The agreement between simulation and experimental results provides support for the proposed model and demonstrates the utility of the flow cytometry/segregated modeling approach for the study of multicopy recombinant vector propagat

ISSN:0006-3592    

DOI:10.1002/bit.260350604

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

年代:1990

数据来源: WILEY

摘要:

AbstractA new fiber‐optic dissolved oxygen sensing technique was applied to the study of two‐phase aqueous/perfluorocarbon (pfc) dispersions. These dispersions were examined for their oxygen transfer enhancement capability in the absence and presence of an oxygen‐consuming reaction. For the pfc‐in‐water dispersions, oxygen uptake rate (OUR) enhancements were equal both with and without oxygen‐consuming cells present in the aqueous phase. In contrast, for water‐in‐pfc dispersions, OUR enhancements inthe presence of reaction were limited by oxygen diffusion across the aqueous phase droplets. Nevertheless, enhancement factors of 5–10 on an aqueous phase volume basis were obtained in a 75% pfc dispersion.These oxygen transfer enhancements were directly translatable into enhancements in overall fermenter productivity for actual microbial cu

ISSN:0006-3592    

DOI:10.1002/bit.260350605

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

年代:1990

数据来源: WILEY

摘要:

AbstractTwo theoretical approaches were examined to quantify observed experimental oxygen transfer enhancements in aqueous/perfluorocarbon (pfc) fermentation systems. Steady‐state macroscopic balance results indicated that enhancements in the presence of reaction were a function of the gas bubble‐to‐droplet diameter ratio for pfc‐in‐water dispersions, but primarily a function of only the droplet diameter for water‐in‐pfc dispersions. The problem of unsteady‐state diffusion into a semi‐infinite composite medium was employed to predict enhancements in the absence of reaction based on the relative permeabilities of the perfluorocarbon and water phases. Since potential enhancements exceeded actual enhancements in the presence of an oxygen consuming reaction for water‐in‐pfc dispersions, the use of less expensive, lower oxygenpermeable oil phases is re

ISSN:0006-3592    

DOI:10.1002/bit.260350606

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

年代:1990

数据来源: WILEY

摘要:

AbstractExperiments have been carried out on a laboratory‐scale adsorber packed with 3.3 kg cornmeal. The effects of varying particle size, feed concentrations and flow rates, and regeneration conditions on the product quality and breakthrough times were investigated. It was found that 85% (w/w) vapor feed gave the best product, and product yields of up to 99.8% (w/w) alcohol were obtained at energy costs as low as 4.0 MJ kg−1. It is suggested how this figure could be impro

ISSN:0006-3592    

DOI:10.1002/bit.260350607

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

年代:1990

数据来源: WILEY

摘要:

AbstractAn intrinsic, unstructured model has been utilized to describethe startup dynamics of a continuous Caalginate‐immobilizedZymomonas mobilis(ATCC 10988) fermentation. This model predicts, at least qualitatively, transients in the fermenter effluent glucose, ethanol, and biomass concentrations as well as radial gradients in immobilized‐cell concentration and activity within the gelbiocatalysts. Predicted intrabiocatalyst gradients in immobilized‐cell specific growth rate were used to calculate the corresponding gradients in intracellular RNA level based on a reported linear relationship between the two. Mathematical simulations of immobilized biomass concentration profiles and RNA content were verified using a novel, scanning microfluorimetry tech

ISSN:0006-3592    

DOI:10.1002/bit.260350608

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

年代:1990

数据来源: WILEY

摘要:

AbstractSimultaneous wet milling and enzymatic hydrolysis of newsprint in a ball mill reactor (BMR) and in an attrition mill reactor (AMR) were studied. The effect of milling on the enzyme deactivation was also investigated. Variables studied included milling media size, material, and the presence or absence of an air–liquid interface in the reactor. At a reaction temperature of 45°C and a pH of 4.5 and in the presence of an air–liquid interface, the amount of reducing sugars produced by hydrolysis using a BMR was typically 5 to 15%less than the amount produced using an AMR. Without an air–liquid interface there was no significant difference. The effect of an air–;liquid interface on enzyme deactivation without any substrate was also studied. Enzyme activity after six hours of milling ranged from 1 to 85% ofthe starting activity. In both the AMR and the BMR, the extent of enzyme deactivation was 20 to 50% greater with an air–liquid interface present than with the air–liquid inte

ISSN:0006-3592    

DOI:10.1002/bit.260350609

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

年代:1990

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260350610

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

年代:1990

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260350611

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

年代:1990

数据来源: WILEY