摘要:

AbstractMilk xanthine oxidase was immobilized by covalent attachment to CNBr‐activated Sepharose 4B and by adsorption ton‐octylamine‐substituted Sepharose 4B. The amounts of activity immobilized for the two preparations were 30 and 90%, respectively. The pH optima for free and adsorbed xanthine oxidase were at 8.6 and 8.2, respectively. Both free and immobilized xanthine oxidase show substrate inhibition. The apparent inhibition constant (Ki′) found for adsorbed xanthine oxidase with xanthine as substrate was higher than theKifor the free enzyme, which was shown to be due to substrate diffusion limitation in the pores of the carrier beads (internal diffusion limitation). Higher substrate concentrations, as desirable for practical application in organic synthesis, can therefore be used with the immobilized enzyme without decreasing the rate. As a result of the internal diffusion limitation the apparent Michaelis constant (Km′) for adsorbed xanthine oxidase was also higher than theKmfor the free enzyme. Immobilized xanthine oxidase was more stable than the free enzyme during storage at 4 and 30°C. Both forms rapidly lost activity during catalysis. The loss was proportional to the amount of substrate converted. Coimmobilization of xanthine oxidase with superoxide dismutase and catalase improved the operational stability, suggesting that O2−and H2O2side‐products of the enzymatic reaction were involved in the inactivation. Coimmobilization with albumin also had some stabilizing effect. Complete surrounding of xanthine oxidase by protein, however, by means of etrapment in a glutaraldehyde‐crosslinked gelatin matrix, considerably enhanced the operational half‐life. This system was less efficient than the Sepharose preparations either because much activity was lost during the immobilization procedure and/or because it had poor flow properties. Xanthine (15 mg)was converted by an adsorbed xanthine oxidase preparation and product (uric acid) was isolated i

ISSN:0006-3592    

DOI:10.1002/bit.260201002

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe production of single‐cell protein (SCP) from ethanol by different imcroorganisms is briefly reviewed. The trends in modeling the SCP production are outlined with a stress on the need to incorporate metabolic and engineering considerations into the pertinent models. Data on batch yeast growth on ethanol are analyzed, a metabolic model involving design parameters is suggested, parameters values are estimated, and their significance is discussed. The model essentially describes the response of a system to disturbances (substrate, metabolites, oxygen, etc.). An effective numerical integration procedure is necessary in the solution of the model which has “stiff” char

ISSN:0006-3592    

DOI:10.1002/bit.260201003

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

年代:1978

数据来源: WILEY

摘要:

AbstractTwo analytically solved mathematical models are presented for a reactor ystem employing immobilized whole cells as a biocatalyst. The whole cells are entrapped or pumped through the shell side of the dialyzer reactor unit. The reactant mixture is circulated through the cialyzer tube side. Nutrient diffuses across the hollow fiber membrane from the tube side to the shell side, where it reacts to form product, which then back diffuses into the reactant mixture stream. The use of a high recirculation ratio of nutrient through the dialyzer tubes to nutrient feed rate to the entire system, allows the system to be modeled as a continuous‐flow stirred‐tank reactor. The first analysis details the development of an effectiveness‐factor correlation for first‐ and zero‐order kinetics. The second analysis presents the solution to an unsteady‐state‐system mass balance with Michaelis–

ISSN:0006-3592    

DOI:10.1002/bit.260201004

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe maintenance coefficient,ms(mmol substrate/g cell dry wt hr), of two distinct groups of C1‐utilizing bacteria has been determined by growing the organisms in an aerobic continuous culture limited by different C1growth substrates. For growth on methanol,ms= 2.5 ± 0.3 forPseudomonasC; 3.9 ± 0.7 forPs. methylotropha(these bacteria utilize methanol via the ribulose monophosphate pathway of formaldehyde fixation) 1.5 ± 0.2 forPseudomonas1, and 2.3 ± 0.4 forPseudomonas135 (the latter bacteria utilize C1‐compounds via the serine pathway). For growth on formaldehyde,ms= 1.5 ± 0.3 forPseudomonas1 and 2.7 ± 0.7 forPseudomonas135, whereas on formate the values formsare 1.0 ± 0.2 and 4.4 ± 1.3; respectively. Although the maintenance coefficients did not differ systematically between the two groups of bacteria, the maintenance requirementsper generationof the serine pathway bacteria were considerably higher (8.7 vs. 3.9) owing to their slower growth rate. The maximum molar yield values,YMmax(g cell dry wt/mol substrate utilized), corrected for the maintenance energy of bacteria which utilize C1‐compounds via the ribulose monophosphate pathway averged 10.1 when grown on methanol, while the values for bacteria which use the serine pathway averaged 13.5. On formaldehyde an average value of 11.5 is obtained and on formate the average value was 7.4 in the serine pat

ISSN:0006-3592    

DOI:10.1002/bit.260201005

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe stability of the model of a completely mixed activated‐sludge process holding the recycle sludge concentration,XR, as a system constant subjected to pH, temperature, potassium cyanide, and phenol shock loading was investigated. Soft‐drink bottling wastewater was used and maintained at 1000 mg/liter chemical oxygen demand (COD). The hydraulic ratio and recycle sludge concentration were maintained at 0.3 and 7000 mg/liter, respectively. An initial dilution rate of ¼ hr−1was maintained for pH and temperature shock loading, with ¼ and ⅛ hr−1for KCN shock loading and ¼, ⅛, and\documentclass{article}\pagestyle{empty}\begin{document}$\frac{1}{16}$\end{document}hr−1for phenol shock loading. It was found that the present system could handle pH shock loading as low as 4.0 and as high as 10.4 without any serious disruption of biological solid concentration and filtrate COD. At pH 4.0 shock loading, filamentous organisms were predominant. Temperature shock loading could be handled from 23 to 36°C without any leakage of effluent filtrate COD. At 46°C temperature shock, a 14 hr period was required to recuperate to the new steady state and provided only 85% of COD removal efficiency. For KCN (50 mg/liger) and phenol (85 mg/liter) shock loading, the dilution rates should be lower than\documentclass{article}\pagestyle{empty}\begin{document}$\frac{1}{16}$\end{document}hr−1in order to shorten the transient period and improve the effluent quality. Biological kinetic constants included cell yield value, maximum growth rate, and the saturation constant, which was varied with the quali

ISSN:0006-3592    

DOI:10.1002/bit.260201006

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

年代:1978

数据来源: WILEY

摘要:

AbstractBy means of stimulus‐response experiments with a Li+tracer, a description of the fluid flow in a 30 m3reactor, used for anaerobic treatment of wastewater, was derived. It appeared that of the three parts that could be distinguished in the reactor (the sludge bed. The sludge blanket, and the settler), the sludge bed could be described as a combination of two perfectly mixed regions with bypassing and return flows; the sludge blanket was perfectly mixed, while the fluid flow in the settler could be described as plug flow. From experiments performed under different conditions it was concluded that 60 m3gas/day were sufficient to provide good mixing and also that the height of the sludge bed should be 2–3 m. From this last conclusion it follows, e.g., that scale‐up of the 30 m3reactor should be done by increasing the cross section of the reactor while homogeneously distributing the influent over the b

ISSN:0006-3592    

DOI:10.1002/bit.260201007

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

年代:1978

数据来源: WILEY

摘要:

AbstractMaterial and energy balances for fermentation processes are developed based on the facts that the heat of reaction per electron transferred to oxygen for a wide variety of organic molecules, the number of available electrons per carbon atom in biomass, and the weight fraction carbon in biomass are relatively constant. Mass–energy balance equations are developed which relate the biomass energetic yield coefficient to sets of variables which may be determined experimentally. Organic substrate consumption, biomass production, oxygen consumption, carbon dioxide production, heat evolution, and nitrogen consumption are considered as measured variables. Application of the balances using direct and indirect methods of yield coefficient estimation is illustrated using experimental results from the literature. Product formation is included in the balance equations and the effect of product formation on biomass yield estimates is examined. Application of mass–energy balances in the optimal operation of continuous single‐cell protein production facilities is examined, and the variation of optimal operating conditions with changes in yield are illustrated for methanol as organic subs

ISSN:0006-3592    

DOI:10.1002/bit.260201008

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

年代:1978

数据来源: WILEY

摘要:

AbstractMaterial and energy balances for fermentation processes with product formation are developed using regularities which are frequently useful in analyzing experimental results. Available electron balances are presented and used to analyze the results of experiments in which biomass and lysine are produced in batch culture using molasses and corn extract as organic substrates. Measured values of biomass productivity, lysine productivity, O2consumption rate, heat evolution rate, CO2evolution rate, and rate of utilization of reducing sugars (RS) are used to obtain estimates of biomass energetic yield, lysine energetic yield, and fraction of substrate energy evolved as heat. For two of the three experiments, based on the entire fermentation, the measured mass rate variables are very consistent and energy measurement errors are less than 10% when proper consideration is given to both the RS and the amino acids present in the organic substrate. The average measured value of 26.5 kcal/equivalent (equiv) of available electrons transferred to oxygen compares favorably with the known average value of 27 kcal/equiv.

ISSN:0006-3592    

DOI:10.1002/bit.260201009

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

年代:1978

数据来源: WILEY

摘要:

AbstractPhanerochaete chrysosporiumwas grown in fermentors on NaOH‐extracted maple, pine, and cedar barks at the optimum substrate concentration of 1% (w/v). The yields (mg protein/liter) on maple, pine, and cedar were 1500, 1200, and 880, respectively, which are probably due to the different lignin contents of the barks. Lignin is not utilized. The productivities at 30°C obtained for pine (4.07 × 10−2g protein/liter hr) and cedar (2.63 × 10−2g protein/liter hr) barks were greater than for maple (2.63 × 10−2g protein/liter hr). The substrate (bark) was the limiting component of the fermentation. Over the 26–38°C temperature range protein productivity increased by a factor of three (1.55 × 10−2vs. 4.61 × 10−2g protein/liter hr) for maple bark. Low agitation rates resulted in an overproduction of cellulase and reduced levels

ISSN:0006-3592    

DOI:10.1002/bit.260201010

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

年代:1978

数据来源: WILEY

摘要:

AbstractApparent kinetics and pH–activity relationships have been determined for glucoamylase and glucose oxidase immobilized on activated carbon using a diimide method. Reaction rate expressions of Michaelis–Menten form adequately approximate the observed kinetics for both enzyme preparations over the ranges of substrate concentrations considered. Influences of external mass transfer as well as substrate and product adsorption on interpretation of the experimental data have been examined. Immobilization of a glucose oxidase–gluconolactonase enzyme mixture has been found to increase substantially the ratio of gluconolactonase to glucose oxidase activities compared to the corresponding activity ratio for these enzymes in sol

ISSN:0006-3592    

DOI:10.1002/bit.260201011

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

年代:1978

数据来源: WILEY