摘要:

AbstractRapid liquid‐liquid extraction of lactate dehydrogenase from muscle by using a low‐cost aqueous bipolymer two‐phase system was achieved by using a centrifugal separator. Extraction of the target enzyme into the upper phase was enhanced by including the dye Procion yellow HE‐3G (bound to polyethylene glycol). The dye acted as an affinity ligand for the enzyme. The isolation of the enzyme was carried out either by using a cell extract or by homogenizing the muscle directly in the system. The latter approach reduced the preparation time with a factor of 0.25. The two methods gave, respectively, 310 and 360 kU lactate dehydrogenase/kg muscle (measured at 22°C). By using a small centrifugal separator, Alfa Laval LAPX 202, 3–5 kg muscle could be processed/h in a 30‐L, two

ISSN:0006-3592    

DOI:10.1002/bit.260300702

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

年代:1987

数据来源: WILEY

摘要:

AbstractUsing commercial immobilized glucose isomerase (SWETASE®, Nagase Co.), the effect of substrate protection on enzyme deactivation has been studied in a batch manner. The data analysis was carried out based on Briggs‐Haldane kinetics in which enzyme deactivation accompanying the protection of substrates was also considered. The protection factor was proposed to elucidate the dependence of the degree of substrate protection. The existence of the protection of glucose isomerase by the substrates has been verified experimentally. Also, the enzyme‐substrate complex deactivates with a decay constant which is one‐half that of the free enzyme. Theoretical analysis of enzyme deactivation with substrate protection offers an effective understanding which is essential for enzyme replacement and process optimi

ISSN:0006-3592    

DOI:10.1002/bit.260300703

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

年代:1987

数据来源: WILEY

摘要:

AbstractPeriodic environmental shifts have been used to induce synchrony in many different microbial populations. In this article, the induction synchrony phenomenon is analyzed using an age distribution model in which the age at which the cells divide is subjected to periodic forcing. It is found that synchrony will occur whenever the period of the forcing lies in the interval between the youngest and the oldest division age that occur in the population during the forcing. The analysis also predicts that under certain conditions it should be possible to obtain a multimodal synchrony in which cells in the population are distributed among a set of discrete, synchronized cell lines. The behavior of the age distribution when the conditions for synchrony are not satisfied is briefly explored. It is found that the age distribution model is able to exhibit a very rich spectrum of possible dynamic behavior. Many of the phenomena observed can be thought of in terms that are familiar from nonlinear analysis, such as stable and unstable limit cycles, period doubling, halving, and chaos. The richness of dynamic behavior opens the possibility that environmental shifts or periodic forcing could be used as a powerful tool in discriminating models of microbial kinetics and cell cycle control.

ISSN:0006-3592    

DOI:10.1002/bit.260300704

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe performance of a continuous vertical packed‐bed reactor with yeast immobilized in carrageenan gel beads is reported. The study focuses on the mathematical modelling of the steady‐state fermentor behavior by means of a tanks‐in‐series model which includes the intrinsic kinetic model and the external mass transfer and internal diffusion‐reaction conditions in

ISSN:0006-3592    

DOI:10.1002/bit.260300705

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn this article, a two‐phase system for the digestion of wastes with a high solid content is simulated. The solids are charged to the hydrolyzer and then leachate recirculation is activated until biodegradation is nearly complete. Several parameters are tested, namely moisture, leachate recirculation flow rate, and hydrolyzer‐methanizer volume ratio. The results show that recirculation rate is an important parameter subject to optimization, with optimal values corresponding to hydrolyzer hydraulic retention times below 1 day. The quantity of recirculating water must be the highest possible. As a consequence, the organic load to the methanizer is reduced, making thus possible the use of a smaller methanizer vol

ISSN:0006-3592    

DOI:10.1002/bit.260300706

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

年代:1987

数据来源: WILEY

摘要:

AbstractAutoflocculation and bioflocculation are considered to be the most promising means for the economical harvesting of microalgae. We have therefore studied these phenomena with cultures ofScenedesmus obliquusproduced during biological tertiary wastewater treatment. The quantity of extracellular polymers produced during ageing of the cultures proved insufficient to initiate bio‐flocculation while the concentration of Ca2+and PO43−of the treated effluent were too low to induce autoflocculation. It has been shown, however, that the algae sediment more readily upon ageing, possibly as a result of increased ceil density. The use of density gradients made with Percoll (a colloidal solution of silica particles) allowed measurement of the true cell density and showed that this increases when cultures enter the declining growth phase. The quality of the biomass thus harvested is, however, considerably impaired, protein content decreasing from 62.7% (dry wt) during the exponential growth phase (day 5) to 14% at the end of cultures (day

ISSN:0006-3592    

DOI:10.1002/bit.260300707

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

年代:1987

数据来源: WILEY

摘要:

AbstractPressed and wilted samples of sweet sorghum [Sorghum bicolor(L.) Moench var. Rio] were ensiled for periods up to 155 days. A kinetic study of the biochemical changes which occurred during ensiling showed that in wilted sorghum ensilage invert sugars and mannitol levels collectively were maintained at 65% of the original ferment able sugar content of the sorghum. The acidic environment produced by ensiling also served as a pretreatment that resulted in enhanced yields of reducing sugar when the sorghum was contacted with cellulolytic enzymes. The quantity of sugar obtained from enzymatic hydrolysis more than compensated for carbohydrate used by organisms during the ensiling process. BothSaccharomyces uvarumandClostridium acetobutylicumwere able to ferment a medium constituted from pressed sorghum juice and the solution resulting from enzymatic hydrolysis of sweet sorghum ensilage.

ISSN:0006-3592    

DOI:10.1002/bit.260300708

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

年代:1987

数据来源: WILEY

摘要:

AbstractA significant increase in extracellular xylanase activity was observed in the mixed culture fermentation ofTrichoderma reeseiD1‐6 andAspergillus wentiiPt 2804 whenA. wentiiinoculation was phased by 15 h.A. wentiiproduced a polysaccharide, chiefly consisting of glucose monomeric units, which was required for expression of maximum xylanase activity. Expression of high activity of xylanase in theA. wentiiphased mixed culture compared to that in eitherT. reeseiorA. wentiisingle cultures appeared to be controlled by the combined action of a polysaccharide produced byA. wentiiand the relative growth of the two fungi in the mixed cultur

ISSN:0006-3592    

DOI:10.1002/bit.260300709

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

年代:1987

数据来源: WILEY

摘要:

AbstractO‐Acetylserine sulfhydrase in the form of a crude extract fromSalmonella typhimuriumLT2 was used for the production ofL‐cysteine fromL‐O‐acetylserine and sodium hydrosulfide at pH 7.0 and 25°C. The two substrates have quite different pH stability relationships.O‐Acetylserine readily rearranges toN‐acetylserine and the rate of this O → N acyl transfer reaction increases at higher pH, temperature, and concentration ofO‐acetylserine. On the other hand, sodium hydrosulfide is more soluble at a higher pH. A stirred‐tank bioreactor with a continuous substrate feed was employed to overcome this problem. TheO‐acetylserine feed was stored at its saturation level (2.05M) at pH 5.0, and the sodium hydrosulfide feed was dissolved at 2.05–2.3Mwithout pH adjustment (pH ≥ 11.5). Both substrates were simultaneously introduced into the bioreactor. The performance of the bioreactor was optimized by employing an automatic feedback control system to regulate the concentration ofO‐acetylserine in the bioreactor. This feedback control system was based on the fact that as the bioconversion proceeds, protons are produced along with cysteine. A pH controller thus detected the decrease in pH and activated the substrate pumps. After mixing in the bioreactor, these two substrate solutions behaved as a base due to the high alkalinity of sodium hydrosulfide. Thus, substrate infusion started when the pH was lower than the set point, i.e., the reaction pH, and stopped when the pH was raised higher than the set point. The amount of substrate introduced was determined by the alkalinity of the mixture of the two substrates, which in turn was controlled by the concentration of sodium hydrosulfide. After optimizing the sodium hydrosulfide concentration and the substrate feed rate, the bioconversion gave a productivity of 3.6 gL‐cysteine/h/g dry cell weightS. typhimurium, anL‐cysteine titer of 83 g/L and a molar yield

ISSN:0006-3592    

DOI:10.1002/bit.260300710

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe presence of anions in solution was found to inhibit the uptake of La3+, Cd2+, Pb2+, UO 2+2, and Ag+byRhizopus arrhizusbiomass. The effects ranged from total inhibition of Cd2+and Pb2+uptake at equimolar concentrations of EDTA to no change in uptake of La3+or UO 2+2at 12‐fold molar excesses of Cl−or CO 2−3. No anion was found to enhance metal uptake levels, and the degree of inhibition generally followed the series:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm EDTA } \ge \ge {\rm SO}_{^{^{^{\rm 4} } } }^{{\rm 2} - } \ge {\rm Cl}^ - \ge {\rm PO}_{^{^{^{\rm 4} } } }^{{\rm 3} - } \ge {\rm glutamate} \ge {\rm CO}_{^{^{\rm 3} } }^{{\rm 2} - } $$\end{document}The chemical equilibrium model REDEQL2 was adapted to treat metal uptake byR. arrhizusbiomass and used to predict the effects of anions in solution. Comparisons with the experimental results are made and discussed in light of the assumptions underlyin

ISSN:0006-3592    

DOI:10.1002/bit.260300711

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

年代:1987

数据来源: WILEY