摘要:

AbstractA kinetic model of the hydrocortisone‐to‐prednisolone transformation byArthrobacter globiformisis constructed using the experimental data obtained in studies of this process. Besides adequately describing experimental data, the model allows one to determine the relation between hydrocortisone oxidation and the level of endogenous substrates in bacterial cells, and the relation between the saturating concentration of hydrocortisone in the enzymic system of bacteria and the content of endogenous substrates in their cells, as well as the regulation of the transmembrane potential and the activation by the uncoupl

ISSN:0006-3592    

DOI:10.1002/bit.260330602

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

年代:1989

数据来源: WILEY

摘要:

AbstractA kinetic model of hydrocortisone transformation was developed in studies of the kinetics of biochemical systems. The regulatory bases of the model are the biosynthesis of steroid‐transforming enzymes and their activity, the level of endogenous substrates, the respiratory chain activity, and the initial concentrations of reagents. When compared, the experimental data completely coincide with the results of the computer modeling, the coincidence being not only qualitative but also quantitative. It indicates that the model suggested can be used for further studies of other transformations of steroid compounds, as well as for transformation of steroid compounds under close‐to‐biotechnological conditions. The results obtained by means of this model permit one to trace in dynamics the behavior of a number of parameters characterizing the process which is very difficult or not feasible to do in a biochemical experiment. The following was shown: (1) the behavior of the respiratory chain (the reversible transition of its oxidized and reduced forms); (2) the change of the transmembrane potential of hydrogen ions within a far larger stretch of time than is feasible to register in a biochemical experiment; (3) the regulation of the activity of 20β‐hydroxysteroid dehydrogenase and 1, 2‐reductase not only by the change in the level of endogenous substrates, but also by means of their biosynthesis; and (4) the regulatory role of 3‐ketosteroid‐1‐

ISSN:0006-3592    

DOI:10.1002/bit.260330603

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

年代:1989

数据来源: WILEY

摘要:

AbstractVarious types of pretreatments are used for biomass conversion of woods. The major objective of most pre treatments is to increase the susceptibility of cellulose and lignocellulose material to acid and enzymatic hydrolysis. In this study, southern mixed hardwoods were pretreated by combined rapid steam hydrolysis (RASH) and organosolv methods. It was found that the major factor in the pretreatment was the RASH temperatures. The organosolv temperature had only a minor effect on the reactivity of the final product. The enzymatic rate studies indicated that the RASH process helps in increasing the accessibility of cellulose to enzymatic hydrolysis and increased the amount of soluble lignin While the organosolv process only removed solubilized lignin. Another effect of the combined treatment was the decreasing of the enzymatic rate relative to a single RASH pretreatment. All hemicellulose is lost during these pretreatments. Three alcohols (methanol, ethanol, and butanol) were studied using a combined RASH organosolv process. At lower temperatures there were small differences between the alcohols; however, at higher temperatures all alcohols were equally effective. At longer RASH times, the percentage of glucose in the final product, as well as the amount of solubilized lignin, increased. However, the longer RASH times led to a decrease in enzymatic rates, Organosolv residence time studies of 15, 30, and 45 minutes displayed little effect on the product. Various wood‐to‐solvent ratios and water‐to‐alcohol ratios had very little effect on the yield of products. The stability of RASH treated material be fore organosolv process was studied under various storage conditions. The storage conditions had no apparent effect on the

ISSN:0006-3592    

DOI:10.1002/bit.260330604

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

年代:1989

数据来源: WILEY

摘要:

AbstractBiofilm development on sand with different heterogeneous inocula was studied in laboratory‐scale methanogenic fluidized bed reactors. Both the course of biofilm formation during reactor start‐up and the bacterial composition of newly developed biofilms at steady‐state were found to be similar irrespective of the type of inoculum applied. Biofilm formation proceeded according to a fixed pattern that could be subdivided in three consecutive phases, designated as the lag phase, biofilm production phase, and steady‐state phase. Methanogenic activity and biomass content of the fluidized bed granules were found to be accurate parameters of the course of biofilm formation. More indirect parameters monitored did not give unambiguous results in all instances. The composition of the newly developed biomass as assessed on the basis of potential methanogenic activities on different substrates and of the concentration of specific methanogenic cofactors was consistent with electron microscopic obser

ISSN:0006-3592    

DOI:10.1002/bit.260330605

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe biological molecule responsible for the suppression of pyritic sulfur in fine coal simulated froth flotation treated with bacteria was identified. Protein was found to be the most effective agent in pyrite suppression of the three cell components (protein, lipid, and carbohydrate) assayed. Coal recovery and ash removal of the flotation process were only slightly reduced by this treatment. Other protein‐containing materials were evaluated for their ability to suppress pyrite flotation. Whey was found to be the most cost‐effective flotation additive of those assayed. The sulfur content of the whey‐treated float was reduced by 84.0% in a synthetically prepared fractionated coal (10.7% sulfur), by a raw whey dosage of 20 μL/g coal. The inorganic sulfur component of a natural high sulfur coal fraction (10.9%) was completely depressed by this whey addition. The effect of particle size and pulp density upon the process were invest

ISSN:0006-3592    

DOI:10.1002/bit.260330606

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe system described is a modified Hospodka's turbidostat. This device helps to measure the maximum growth rate of fungi in steady‐state aerobic conditions with defined and independent concentration of dissolved oxygen, biomass, and substrate even unlimited. The principle consists of a turbidostat controlled by the dissolved oxygen concentration. The inlet medium pump operates when the dissolved oxygen concentration falls below the set point value. This method allows us to study independently effects of different physical and chemical variables on the maximum specific growth rate of microorganisms. A fungus,Fusarium oxysporum 47isolated from soil, does not show a depressive effect on growth when dissolved oxygen concentration decreases to 5% and osmotic potential to ‐25 bars. Increasing biomass concentration in the range 0.1‐1.0 g/L appears to depress markedly the maximum growth

ISSN:0006-3592    

DOI:10.1002/bit.260330607

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

年代:1989

数据来源: WILEY

摘要:

AbstractAn extensivein vivostudy of the electrokinetic properties of six strains of the brewing yeastS. cerevisiaehas been carried out. The yeasts were cultured under laboratory conditions. They were electrokinetically characterized by the electro‐osmotic dipped cell technique, and data are presented as zeta‐potentials. The effects of pH, fermentation time, successive fermentation cycles, and initial wort density have been established. The electrokinetic properties of an ale yeast which did not function correctly during commercial fermentation have also been examined. The results are discussed in the context of two controversial topics concerning the mechanism of yeast flocculation, the relative importance of yeast cell wall carboxyl and phosphate groups and the influence of wort compone

ISSN:0006-3592    

DOI:10.1002/bit.260330608

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe development of a coimmobilized mixed culture sys tem of aerobic and facultative anaerobic microorganisms in Ca‐alginate gel beads and the production of useful metabolites by the system were investigated. A coimmobilized mixed culture system ofAspergillus awamori(obligate aerobe) andSaccharomyces cerevisiae(facultative anaerobe) in Ca‐alginate gel beads was used as a model system, and ethanol production from starch by the system was used as a model production. MoldAsp. awamoriis an amylolytic microorganism while yeastS. cerevisiaeis an ethanol producer. The two microorganisms grew competitively in the oxygen‐rich surface area of the gel beads because they had similar oxygen demands in aerobic culture conditions. Neither microorganism exhibited “habitat segregation” in the gel beads and leaked yeast cells grew aerobically without ethanol production in the broth. Ethanol productivity was low under these conditions.A more desirable coimmobilized mixed culture system ofAsp. awamoriandS. cerevisiaewas established by adding Vantocil IB (a biocidal compound) to the production medium. The antimicrobial activity of Vantocil IB was more effective withS. cerevisiaethan withAsp. awamori, so that a dense mycelial layer ofAsp. awamoriformed in the surface of the gel beads WhileS. cerevisiaegrew densely in the more inner areas of the gel beads. Also, yeast cell leakace was repressed and ethanol productivity was improved. The system with Vantocil IB produced ethanol of 4.5 and 12.3 g/L from 16 and 40 g/L starch, respectively. A continuous culture using this system with Vantocil IB was also carried out, and a stable steady state could be maintained for six days without leakage of yeast cells and contamination. The selection of a factor suitable for producing “habitat segregation” enabled the development of a coimmobilized mixed culture system of an aerobe and a facultative anaerobe. In this study, totalhabitat segregationwas used to denote a tendency to exhibit denser growth in different parts of

ISSN:0006-3592    

DOI:10.1002/bit.260330609

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

年代:1989

数据来源: WILEY

摘要:

AbstractMouse hybridoma cells were grown in suspension in continuous stirred bioreactors. Cell growth, substrate utilization, and monoclonal antibody (MAb) production were studied using serum‐free medium. Steady‐state data were obtained at different dilution rates, between 0.012 and 0.039 h−1Viability was profoundly affected by dilution rate, particularly near the lower end of the dilution‐rate range investigated. MAb concentration and productivity went through a maximum with respect to dilution rate. Lactate yield on glucose declined with in creasing dilution rate. Experiments were carried out to study the effects of medium glucose concentration on cell growth, product formation, and lactate yield on glucose. Reduction of glucose concentration in the feed medium did not considerably affect cell density and MAb concentration in the culture, but lactate levels dropped sharply; lactate yield on glucose declined substantially, indicating alterations in cell metabolic path ways for energy metabolism. Optimization strategy for continuous cell culture is di

ISSN:0006-3592    

DOI:10.1002/bit.260330610

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of hydrodynamic forces on cell growth are investigated for animal cells growing on microcarriers. A reduction in net growth was observed with high levels of agitation. DNA measurements indicated that the reduction in net growth was due entirely to cell death, from hydrodynamic forces. No inhibition or enhancement of cell replication appeared to occur with high levels of agitation.

ISSN:0006-3592    

DOI:10.1002/bit.260330611

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

年代:1989

数据来源: WILEY