摘要:

AbstractThe specific ethanol productivity withSaccharomyces cerevisiaegrown aerobicly in a chemostat was found to be highly dependent on the ratio of intracellular to extracellular potassium concentration through variations in the energy consumption used for maintenance of the concentration gradient of potassium across the cell membrane. The specific ethanol productivity progressively rose from 0 to 20 mmol h−1g−1cell dry matter at a growth rate of 0.17 h−1when the ratio of intracellular to extracellular potassium concentration was increased from 10 to 80. The ethanol production under potassium limited growth conditions was caused neither by a reduction in the specific respiratory activity nor by variations in the potassium content in cell dry matter. Results which strongly that ethanol production under potassium limited growth conditions is brought about by changes in the ratio of pyruvate oxidase to pyruvate decarboxylase activity through changes in the intracellular pyruvate concentration are pres

ISSN:0006-3592    

DOI:10.1002/bit.260260402

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe cultural conditions for the production of enhanced formation of L‐serine (up to 7 g/L) are described with the methylotrophic bacteriumPseudomonas3 ab (DSM 672). The batch process is divided into three parts: (1) the biomass production phase, (2) substrate limitation period, and (3) L‐serine accumulation phase. The initial specific production rate ofqp= 0.1 g L‐serine/g dry wt/h is based on the inhibition of the L‐serine pathway. This is accomplished by high precursor concentrations (glycine) and a pH shift to pH 8.5. The enzymatic background is discussed. Furthermore, a coupling of the L‐serine process with a L‐tryptophan‐producing process is

ISSN:0006-3592    

DOI:10.1002/bit.260260403

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

年代:1984

数据来源: WILEY

摘要:

AbstractUsing only wheat bran koji from theRhizopusstrain, raw cassava starch and cassava pellets converted reasonably well to alcohol (ethanol) without cooking at 35°C and pH 4.5–5.0. When the initial broth contained 30 g raw cassava starch, 10 gRhizopussp. koji, and 100 mL tap water, 12.1 g of alcohol was recovered by final distillation from fermented broth. In this case, 12.1 g alcohol corresponds to an 85.5% conversion rate based on the theoretical values of the starch content. When the initial broth contained 40 g cassava starch, 14.1 g of alcohol was recovered, where 14.1 g corresponds to a 74.5% conversion rate. The alcoholic fermentation process described in the present work is considered more effective and reasonable than the process using raw starch without cooking reported until now, since the new process makes it unnecessary to add yeast cells and glucoamylase preparati

ISSN:0006-3592    

DOI:10.1002/bit.260260404

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe kinetics of crystalline cellulose and hemicellulose hydrolysis in corn stover were studied with a nonisothermal technique. Reactions were arrested at temperatures between 160 and 240°C and product sugars were analyzed using a Bio‐Rad HPX‐85 liquid chromatographic column. A simple first‐order series reaction model was used for both cellulose and hemicellulose hydrolysis reactions. Kinetic parameters were obtained for three different sulphuric acid concentrations (0.49, 0.92, and 1.47 wt %). Activation energies remained constant over this acid concentration range but the preexponential factors showed an increase with acid concentration. Relationships were obtained between the preexponential factors and acid concentrations. Cellulose hydrolysis and glucose degradation reactions were observed to be of higher order with respect to acid concentration in comparison with the previous studies with other raw mat

ISSN:0006-3592    

DOI:10.1002/bit.260260405

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

年代:1984

数据来源: WILEY

摘要:

AbstractOptimal automatic bioreactor control requires a mathematical model adapted to the potency of reliable sensors. A new relationship describing the kinetic behavior of alcoholic fermentation is discussed. By analogy with chemical kinetics, the biological rate of substrate consumption is related to substrate and product concentration by the following equation:\documentclass{article}\pagestyle{empty}\begin{document}$$r_s = kS^\alpha P^\beta$$\end{document}Using the well known yield relation between product and substrate, it is possible to describe in both batch and continuous cultures the ethanol and sugar concentrations versus time. This pattern has been successfully tested on several fermentations performed by yeasts (S. cerevisiae, S. bayanus, andS. cerevisiae sake) and a bacterium (Z. mobilis). This simple relationship is proposed as a tool for process control alcoholic fermentation.

ISSN:0006-3592    

DOI:10.1002/bit.260260406

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe effect of dehydration on yield and calorific values has been investigated for oils, hydrocarbons, and polyphenols extracted from leaves of Euphorbia esula/ (leafy spurge). Methods of dehydration employed were with a warm oven (50°C), a hot oven (105°C), at room temperature (25°C), and with freeze drying. Generally, dehydration resulted in a loss of yield for all extractives. Noteworthy exceptions were oil yields from the warm‐oven‐ or air‐dried biomass which did not differ significantly from fresh tissue. Significant differences in calorific values (range 4643–5192 cal/g) were observed for each category of whole leafy biomass dehydrated as indicated above. Dehydration reduced the calorific value of oils (range 9483–10,095 cal/g) but tended to increase the calorific values of polyphenols (range 4178–6033 cal/g). NMR spectroscopy of the oil fraction suggested that dehydration did not grossly alter the composition of oils, despite differences in yield and ca

ISSN:0006-3592    

DOI:10.1002/bit.260260407

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe rate of celluose degradation, limited due to the inhibition by cellobiose, can be increased by the hydrolysis of cellobiose to glucose using immobilized β‐glucosidase. Production of β‐glucosidase in four yeasts was studied and a maximum activity of 1.22 IU/mg cells was obtained in cells ofPichia etchellsiiwhen grown on 3% cellobiose as the sole carbon source. A study of the immobilization of β‐glucosidase containing cells ofPichia etchellsiion various solid supports was conducted and immobilization by entrapment in calcium alginate gel beads was found to be the most simple and efficient method. A retention of 96.5% of initial activity after ten sequential batch uses of the immobilized preparation was observed. The pH and temperature optima for free and immobilized cells were the same, i.e., 6.5 (0.05MMaleate buffer) and 50°C, respectively. Even though the temperature optimum was found to be 50°C, the enzyme exhibits a better thermal stability at 45°C. Beads stored at 4°C for six months retain 80% of their activity. Kinetic studies performed on free and immobilized cells shown that glucose is a noncompetitive product inhibitor.The immobilized preparation was found to be limited by pore diffusion but exhibited no film‐diffusion resistance during packed bed column indicated by a low dispersion number of 0.1348. A model for reaction with pore diffusion for a noncompetitive type of inhibited system was developed and applied to the cellobiose hydrolysis system. The rate of reaction with diffusional limitations was determined by using the model and effectiveness factors were calculated for different particle sizes. An effectiveness factor of 0.49 was obtained for a particle diameter of 2.5 mm. The modified rate expression using the effectiveness factor represented batch and packed bed reactor operation satisfactorily. The productivity in the packed bed column was found to fall rapidly with increase in conversion rate indicating that the operating conditions of the column would have to be a compromise between high conversion rates and reasonable productivity. A half‐life of over seven days was obtained at the operating temperature of 45°C in continuous operation of the packed bed reactor. However, the half‐life in the column was found to be greatly affected by temperature, increasing to over seventeen days at a temperature of 40°C and decreasing to less t

ISSN:0006-3592    

DOI:10.1002/bit.260260408

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

年代:1984

数据来源: WILEY

摘要:

AbstractInvertase immobilized onto corn grits was utilized in the hydrolysis of highly concentrated sucrose solutions producting liquid sugar solutions containing glucose and fructose. Comparisons of conversion efficiencies of this immobilized invertase in a continuous stirredtank reactor and a plug‐flow reactor indicated that the plug‐flow reactor has an higher efficiency. Continuous sucrose hydrolysis was then performed in 0.1‐ and 1‐L tubular reactors. This tenforld scaling‐up was achieved without any noticeable loss in efficiency. This process thus was scaled‐up to a 17.6‐L pilot reactor set in a cane sugar refinery. This reactor was fed with highly concentrated sucrose solutions [71% (w/w)] to produce invert sugar syrup with the desired inversion degree. It allows a productivity equal to 9.1 kg sucrose hydrolyzed/h in the case of a 69% (w/w) sucrose initial concentration with a 72% co

ISSN:0006-3592    

DOI:10.1002/bit.260260409

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

年代:1984

数据来源: WILEY

摘要:

AbstractA mathematical model has been developed which describes organics removal, oxygen utilization, ammonianitrogen removal, ortho‐phosphate removal, and biomass production in an aggregated microbial suspension containing a uniform floc size and the organics as a soluble biodegradable material. It is applicable to both steady‐state and transient conditions, as well as to systems experiencing only carbon oxidation or to systems experiencing both carbon oxidation and nitrification. The model, consisting of five partial differential equations and four ordinary differential equations, takes into account the flow pattern in the reactor, intraparticle mass transport of oxygen, organics, ammonia‐nitrogen and ortho‐phosphate, and biochemical reactions by the individual cells embedded in t

ISSN:0006-3592    

DOI:10.1002/bit.260260410

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

年代:1984

数据来源: WILEY

摘要:

AbstractIt is known that 2,3‐butanediol is a potentially valuable chemical feedstock that can be produced from the sugars present in hemicellulose and celluose hydrolysates.Klebsiella oxytocais able to ferment most pentoses, hexoses, and disaccharides. Butanediol appears to be a primary metabolite, excreted as a product of energy methabolism. The theoretical maximum yield of butanediol from monosaccharides is 0.50 g/g. This article describes the effects of pH, xylose concentration, and the oxygen transfer rate on the bioconversion of D‐xylose to 2,3‐butanediol. Product inhibition by butanediol is also examined. The most important variable affecting the kinetics of this system appears to be the oxygen transfer rate. A higher oxygen supply favors the formation of cell mass at the expense of butanediol. Decreasing the oxygen supply rate increases the butanediol yield, but decreases the overall conversion rate due to a lower cell concentr

ISSN:0006-3592    

DOI:10.1002/bit.260260411

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

年代:1984

数据来源: WILEY