摘要:

AbstractLiquid extraction is one means of removing metabolic products continuously during a fermentation and so reducing product inhibition. It is known that microbial organisms are attracted to liquid‐liquid interfaces, and it is important for the design of extraction systems to establish if this has a detrimental effect on the rate of extraction. The extraction of ethanol from aqueous suspensions of yeast (Saccharomyces cerevisiae) usingn‐ decanol is described in this paper. It was found that the presence of the yeast cells severely reduced the rate of ethanol extraction. The overall mass transfer coefficient was reduced from 5.0 × 10−6to 0.7 × 10−6m/s. This reduced overall mass transfer coefficient was unaffected by yeast concentration in the range 0.1–20 kg/m3. The results are consistent with the yeast cells adsorbing to the interface in closely packed layers and preventing mass transfer by simply reducing the available interfacial area. Optical microscope observations confirmed that a yeast layer several cell diameters thick rapidly built up at the interface when a small decanol droplet was added to a yeast

ISSN:0006-3592    

DOI:10.1002/bit.260280702

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe growth kinetics of the yeastSaccharomyces cerevisiaeand the production rate of ethanol have been studied in batch fermentation under anaerobic conditions in a 20‐L fermentor. Two substrates were used in fermentation trials: a synthetic mixture of three fermentable sugars, D‐glucose, D‐mannose, and D‐galactose, and a low‐yield liquor originating from a bisulfite cooking process. The Monod model adequately described the system in relation to the specific growth rate μxand the specific product formation rate μP. Different fermentation parameters (growth rate, substrate utilization, and product formation) were determined for the synthetic mixture and the bisulfite liquor. It was observed that the specific growth rate is much lower in spent sulfite liquor than in a synthetic medium. However, the specific product formation rate remains the same in

ISSN:0006-3592    

DOI:10.1002/bit.260280703

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

年代:1986

数据来源: WILEY

摘要:

AbstractMany of the sophisticated sensors desirable for monitoring bioreactors cannot be placed in the bioreactor either because they are not steam sterilizable or because they require nonphysiological operating conditions. Such sensors can be used if they are separated from the bioreactor. Separation of the sensor from the bioreactor causes a time lag in data acquisition. This results in several complexities in the development of an appropriate and stable feedback control system based on a separated sensor. This paper analyzes the optimal control of a bioreactor with a separated sensor without a time lag and analyzes the feedback control (but not necessarily the optimal control) with a time lag. Simulation results indicate that this type of analysis could be extended to more general bioreactor operating conditions.

ISSN:0006-3592    

DOI:10.1002/bit.260280704

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

年代:1986

数据来源: WILEY

摘要:

AbstractGround corn is now used in industry as an adsorbent to remove water from ethanol vapors. It is stable and inexpensive at 10 cents/lb (22 cents/kg). For regeneration it requires less than 2000 Btu/gal of 190 proof ethanol processed. If necessary, it could be readily saccharified and fermented into ethanol after use. This renewable resource has further exciting potential as an inexpensive adsorbent for water removal from other alcohols, including methanol, isopropanol, andt‐butanol. Water sorption capacity in a fixed bed, nonisothermal adsorption column appears to be a function of the heat capacity of the non‐adsorbed alcohol vapor, relative to the heat capacity of the corn adsorbent. Methanol, ethanol, isopropanol, andt‐butanol containing 17.5 mol% water gave 105,151, 284, and 358 g anhydrous product/kg adsorbent, respectively, per adsorption cycle. This adsorbent, having operational temperature ranges between 80 and 100°C, is indicated to be of potential utility in solvent recycle processes using these industrially important alcohols. Observed adsorption characteristics are discussed in terms of the alcohol properties of molecular size, heat capacity, and diffusivity. The adsorption mechanism is hypothesized to include transport of water molecules into the structure of adjacent starch molecules present in small spherical bodies (diameter of several microns) immobilized on the surface of the corn grit par

ISSN:0006-3592    

DOI:10.1002/bit.260280705

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of the presence of more easily degradable alternative carbon sources on the biodegradation of toxic waste components is of great practical importance. In this work, a mixed phenol/glucose waste was fed to two heterogeneous populations acclimated to different conditions: one was acclimated to phenol as a sole source of carbon and one to a mixed phenol/glucose substrate. Batch substrate utilization experiments were performed under both growth and nonproliferating (no medium nitrogen source) conditions in order to assess substrate removal patterns at the levels of enzyme production and enzyme function. The results indicated that the substrate removal pattern exhibited by the cells was significantly influenced by the acclimation characteristics of the culture. The phenol acclimated cells showed an initial preference for phenol, but the presence of glucose hindered phenol removal rate under both growth and nonproliferating conditions. The cells acclimated to the mixed phenol/glucose waste demonstrated rapid initial glucose removal with a slower concomitant utilization of phenol; acclimation to the mixed waste evidently had a significant impact on the substrate removal pattern for this mixed substrate system.

ISSN:0006-3592    

DOI:10.1002/bit.260280706

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe data on ethanol‐water vapor‐liquid equilibrium in the presence of cellulase enzyme, nutrients, yeast, and rice straw indicated a substantial increase in ethanol concentration in vapor phase at reduced pressures. Maximum relative volatility of ethanol in the presence of added components is approximately twice that of a pure ethanol‐water system. The equation correlating the activity coefficient and ethanol concentration in the liquid phase adequately represents the equilibrium beh

ISSN:0006-3592    

DOI:10.1002/bit.260280707

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

年代:1986

数据来源: WILEY

摘要:

AbstractA series‐type enzyme deactivation model is used to model and to quantitate some more complex enzyme deacti‐vations. The influence of temperature, pH, immobilization, chemical modifier (inhibitor or protector), substrate, and metal ion on the inactivation kinetics and on the parameter values is examined. In some cases the influence of two parameters on enzyme inactivations is presented. This provides further physical insights into enzyme inactivation and stabilization proces

ISSN:0006-3592    

DOI:10.1002/bit.260280708

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn order to predict the potential benefit associated with mixing devices designed to introduce periodic light modulations in dense cultures of microalgae, it is necessary to develop a quantitative understanding of the relationship between the frequency of the modulations and the resulting photosynthetic efficiency enhancement. To explore this relationship, the photosynthetic rate of cells ofPhaeodactylum tricornutumfrom a dense steady state culture was determined as a function of modulation frequency, intensity of light received, and the proportion of the total cycle period during which the cells were illuminated. At high flash frequencies, the photosynthetic rate was determined by the average intensity received by the cells (full light intensity integration), while at low frequencies the cells responded to the instantaneous intensity (no light intensity integration). Full integration was approached asymptotically with increasing flash frequency. The frequency response could be described by a rectangular hyperbola, and the parameters of this hyperbola were nearly independent of the illumination intensity and the flash proportion. The saturation constant of the hyperbola, at which the response is one‐half of the maximum, was 0.67 H

ISSN:0006-3592    

DOI:10.1002/bit.260280709

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

年代:1986

数据来源: WILEY

摘要:

AbstractWidely applied selection strategies for plasmid‐containing cells in unstable recombinant populations are based upon synthesis in those cells of an essential, selection gene product. Regular partitioning of this gene product combined with asymmetric plasmid segregation produces plasmid‐free cells which retain for some time the ability to grow in selective medium. This theory is elaborated here in terms of a segregated model for an unstable recombinant population which predicts population growth characteristics and composition based upon experimental data for stable strain growth kinetics, plasmid content, and selection gene product stability. Analytical solutions from this model are compared with an unsegregated phenomenological model to evaluate the effective specific growth rate of plasmid‐free cells in selective medium. Model predictions have been validated using experimental growth kinetics and flow cytometry data forSaccharomyces cerevisiaeD603 populations containing one of the plasmids YCpG1ARS1, YCpG1ΔR8, YCpG1ΔR88, YCpG1ΔH103, YCpG1ΔH200, pLGARS1, and pLGSD5. The recombinant strains investigated encompass a broad range of plasmid content (from one to 18 plasmids per cell) and probability α of plasmid loss at division (0.05 ≤ α ≤ 0.42). Experimental data for all strains considered is inconsistent with the hypothesis that plasmid‐free cells are unable to grow in selective medium. For a given value of a, the fraction of plasmid‐containing cells in the population decreases with increasing plasmid content and increases for less stable selection gene products. This conceptual framework and mathematical model will aid in strain development for greater

ISSN:0006-3592    

DOI:10.1002/bit.260280710

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe time course of the peroxidative bromination of propylene accompanied byin situgeneration of hydrogen peroxide by glucose oxidase was examined to improve the productivity of propylene bromohydrin. To prevent the rapid inactivation of lactoperoxidase by excess hydrogen peroxide, it was effective to use lactoperoxidase in large excess as compared with glucose oxidase, and to raise the concentration of bromide ion. However, the rate of glucose consumption was lowered at high concentrations of bromide ion, and at higher mole fraction of oxygen as compared with propylene in the gas mixture. Therefore, it seemed that for the favorable production of bromohydrin there existed the optimal conditions for the concentration of bromide ion and for the composition of oxygen‐propylene gas mixture. Such kinetic behaviors of the sequential enzymatic reactions were explained by a mechanism involving free hypobromous acid as a reactive intermediate. Furthermore, the stability of the coimmobilized enzymes withk‐carrageenan gels was investigated in continuous operations. The half‐life of the enzymes was ca. 60 h for the production of propylene bromoh

ISSN:0006-3592    

DOI:10.1002/bit.260280711

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

年代:1986

数据来源: WILEY