摘要:

AbstractThe adsorption of aluminum ions bySaccharomyces cerevisiaehas been investigated by determining adsorption isotherms and electrophoretic mobility. The adsorption of aluminum ensures a neutralization of the cell surface charge and allows adhesion of the cells to glass and polycarbonate. Glass slides have been taken as a negatively charged model support, allowing the authors to study in detail the process of adhesion. The cells are simply pretreated by an aluminum solution near pH 4. Bringing the Al‐pretreated cells in contact with the support by sedimentation and washing the support and sediment makes it possible to obtain a single, dense, regular layer of cells adhering strongly to the support. Adhesion can also be obtained from a suspension flowing parallel to a vertical support, provided the flow velocity is sufficiently small; the amount of cells immobilized per unit support area is about one‐half that obtained by sedimentation. The immobilized cells show a specific activity for ethanol production from glucose which is similar to cells in suspens

ISSN:0006-3592    

DOI:10.1002/bit.260270302

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

年代:1985

数据来源: WILEY

摘要:

AbstractAlkaline solutions of hydrogen peroxide partially delignify wheat straw and other lignocellulosic materials, leaving a cellulosic residue that is highly susceptible to enzymatic digestion by cellulase. The delignification reaction is strongly dependent upon the pH of the reaction mixture, with an optimum at pH 11.5–11.6, pKa for the dissociation H2O2⇌ H++ HOO−. The data are consistent with a mechanism in which H2O2decomposition products such as ·OH and O 2−·, rather than H2O2or HOO−, are the primary lignin oxidizing species. During the course of the delignification reaction, O2is evolved from the reaction mixture indicating active H2O2decomposition. At a given concentration of H2O2, the rate of O2evolution is proportional to the amount of lignocellulosic substrate present in the reaction mixture. However, the total amount of O2evolved is inversely proportional to the amount of substrate present, indicating that some of the peroxide oxygen becomes incorporated into lignin degradation products. The amount of peroxide oxygen incorporated can range as high as 2 O2per lignin C9unit, depending upon the initial concentration of lignocellulo

ISSN:0006-3592    

DOI:10.1002/bit.260270303

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

年代:1985

数据来源: WILEY

摘要:

AbstractFirefly luciferase fromPhotinus pyralishas been covalently bound to a collagen strip via an acylazide activation process. Immobilization performed in the presence of both substrates ATP and luciferin allows to increase the activity retained on the strip. The best activity exhibited by immobilized luciferase was obtained in a 0.05MTris‐acetate buffer, pH 7.75. The pH optimum and the activation energy of luciferase have been found unchanged after immobilization. In the chosen stirring conditions, no diffusional limitations of substrates appear. ATP measurements can be performed with collagen‐bound luciferase in the range 1.10−11M−3.10−6M. It was possible to store the strips at 4°C in a dehydrated form; then, the bound enzyme retains 20% of its initial activity after eight months. Human blood ATP was measured with this collagen‐bound luciferase and the results were found in good agreement with those obtained by solubl

ISSN:0006-3592    

DOI:10.1002/bit.260270304

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

年代:1985

数据来源: WILEY

摘要:

AbstractA new method of continuous process analysis in fermentation using a mass spectrometer (MS) membrane probe is described. A number of samples from industrial fermentations were analyzed for the occurrence of volatiles detectable with a silicone membrane probe connected to a quadrupole MS. In all fermentations, characteristic spectra were observed which were found to change systematically during the batch process. Factor analysis was used to treat the data. The factor scores were compared with the actual product concentrations (antibiotics, toxins, etc.), which were measured using other analytical methods and were found to correlate with them. On‐line analysis was also carried out on a fermentation with an MS and an Apple II microcomputer. Direct monitoring of products, which are not directly measurable with the membrane MS probe requires a new calibration each time conditions such as medium composition are change

ISSN:0006-3592    

DOI:10.1002/bit.260270305

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

年代:1985

数据来源: WILEY

摘要:

AbstractHydrolysis ofL‐ andD‐O‐phosphothreonines catalyzed by four different phosphatases, alkaline phosphatases from calf intestine andE. coliand acid phosphatases from wheat germ and potato, has been kinetically studied. Alkaline phosphatases were found to have comparable reactivities towards the optical isomers. On the other hand, both acid phosphatases displayed a marked stereoselectivity, hydrolyzing the L‐ester much faster than its D counterpart. Wheat germ acid phosphatase was the most stereoselective enzyme:VL/VD= 24 andKm,L/Km,D= 0.17. This enzyme was immobilized (ink‐carrageenan gel, followed by crosslinking with glutaraldehyde) and used for the preparative resolution ofD,L‐threonine: the latter was first chemicallyO‐phosphorylated and then asymmetrically hydrolyzed by the immobilized phosphatase. As a result, gram quantities ofL‐threonine of high optical purity andO‐phospho‐D‐threonine were prepared. Immobilized wheat germ phosphatase has been tested for the resolution of other racemic alcohols: serine, 2‐amino‐1‐butanol, 1‐amino‐2‐propanol, 2‐octanol, and menthol. In all those cases, the enzyme was either not sufficiently stereoselective or t

ISSN:0006-3592    

DOI:10.1002/bit.260270306

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

年代:1985

数据来源: WILEY

摘要:

AbstractA mathematical model has been developed to simulate the pseudo‐crystallofermentation process of hydrocortisone byArthrobacter simplex. The model describing the process included considerations on the kinetics of microbial growth, the rate of enzyme formation, the rate of substrate dissolution, the rate of solute crystallization, and the kinetics of enzymatic reaction. The system of equations was solved numerically by the Runge‐Kutta‐Gill method. The good agreement between prediction and experiment indicated the reliability of the established model. The simulation was capable of predicting the time when the crystallization of product occurred, which could be further verified by microscopic observation on the culture medium, as well as cell growth, enzyme synthesis, product formation, and the composition of the final product cry

ISSN:0006-3592    

DOI:10.1002/bit.260270307

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

年代:1985

数据来源: WILEY

摘要:

AbstractSynergistic action of α‐amylase and glucoamylase on hydrolysis of starch is modeled by the kinetic equations presented in this paper. At the early stage of the reaction α‐amylase acts as a contributor of newly formed nonreducing ends of starch molecules to glucoamylase by splitting the original starch molecules. This is expressed by the simultaneous differential equations which consist of each rate equation for α‐amylase and glucoamylase. After the molecular weight of the substrate decreases to the value of about 5000, which is obtained experimentally in this work, the action of α‐amylase can be neglected and the rate of formation of glucose obeys only the rate equation for g

ISSN:0006-3592    

DOI:10.1002/bit.260270308

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe technical feasibility of adopting the fixed‐film reactor concept for biogas production from screened dairy manure was investigated. The methane production capability of laboratory‐scale 4‐L anaerobic reactors (conventional and fixed‐film) receiving screened dairy manure and operated at 35°C was compared. Dairy manure filtrate with 4.4% total solids (TS) and 3.4% volatile solids (VS) (average value) was prepared from 1:1 manure–water slurry. The feed material was added intermittently at loading rates ranging from 2.34 to 25 and 2.25 to 785 g VS/L d, respectively, for the conventional and fixed‐film reactors. Maximum methane production rate (L CH4/L d) for the conventional reactor was 0.63 L CH4/L d achieved at a 6‐day hydraulic retention time (HRT). For the fixed‐film reactor the maximum production rate was 3.53 L CH4/L d when operated at a loading rate of 262 g VS/L d (3 h HRT). The fixed‐film reactor was capable of sustaining a loading of 785 g VS/L d (1 h HRT). The fixed‐film reactor performed much better than the conventional reactors. These results indicate that a large reduction of required reactor volume is possible through application of a fixed‐film concept combined with a liquid–solid separation pret

ISSN:0006-3592    

DOI:10.1002/bit.260270309

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

年代:1985

数据来源: WILEY

摘要:

AbstractZymomonas mobiliscells were entrapped in K. carrageenan. Growth was observed with the immobilized cell preparation. The kinetic and yield parameters for the conversion of fructose to ethanol were nearly identical to free cells. The same preparation of immobilized cells was used in six repeated batch runs and at the end sixthbatch fructose was converted to ethanol more rapidly and efficiently with ethanol productivity of 14 g/L h and 96% conversion of fructose. The effect of high fructose and ethanol levels on specific fructose uptake rate and ethanol productivity was studied and quantitatively analyzed.

ISSN:0006-3592    

DOI:10.1002/bit.260270310

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe inhibitory effect of ethanol on yeast growth and fermentation has been studied for the strainSaccharomyces cerevisiaeATCC No. 4126 under anaerobic batch conditions. The results obtained reveal that there is no striking difference between the response of growth and ethanol fermentation. Two kinetic models are also proposed to describe the kinetic pattern of ethanol inhibition on the specific rates of growth and ethanol fermentation:\documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {\frac{{\mu _i }}{{\mu _0 }} = 1{\rm } - {\rm }\left( {\frac{P}{{P_m }}} \right)^\alpha } \hfill & {\left( {{\rm for}\ {\rm growth}} \right)} \hfill \\ {\frac{{\nu _i }}{{\nu _0 }} = 1{\rm } - {\rm }\left( {\frac{P}{{P'_m }}} \right)^\beta } \hfill & {\left( {{\rm for}\ {\rm ethanol}\ {\rm production}} \right)} \hfill \\ \end{array}$$\end{document}The maximum allowable ethanol concentration above which cells do not grow was predicted to be 112 g/L. The ethanol‐producing capability of the cells was completely inhibited at 115 g/L ethanol. The proposed models appear to accurately represent the experimental data obtained in this study and the literature dat

ISSN:0006-3592    

DOI:10.1002/bit.260270311

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

年代:1985

数据来源: WILEY