摘要:

AbstractThe adsorption ofThiobacillus ferrooxidansto coal surfaces has been studied. Adsorption experiments were conducted on coal samples from eight different Eastern coal fields. In all cases the adsorption process was at least 90% complete within the first two minutes following inoculation. The results of these experiments were used to test the validity of two proposed adsorption models. The first model assumes that bacterial adsorption follows second‐order irreversible kinetics of the second kind with respect to the concentration of bacteria and substratum surface area in the system. The second model allows for the contribution of reversible adsorption detected in desorption experiments. It was found that the combined reversible–irreversible model more accurately describes the initial stages of adsorption. Rate constants in both models were calculated for each coal sample. The relation of each of these constants to the pyrite concentration in coal is presented and the significance of these relations is discussed.Scanning electron micrographs of inoculated coal samples sho thatThiobacillus ferrooxidansselectively adsorb to exposed pyrite phases dispersed throughout the organic coal matrix. Preferential attachment was also observed along topographical faults in the caol surface. Mercury contact angle measurements on coal indicate that the selective adsorption ofThiobacillus ferrooxidansmay be attributable to the lower surface free energy of pyrite relative to the organic coal mat

ISSN:0006-3592    

DOI:10.1002/bit.260280402

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

年代:1986

数据来源: WILEY

摘要:

AbstractSugarcane bagasse and wheat straw were subjected to alkali treatment at 200°C for 5 min and at 3.45 MPa gas pressure (steam and nitrogen), followed by an explosive discharge through a defibrating nozzle, in an attempt to improve the rate and extent of digestibility. The treatment resulted in the solubilization of 40–45% of the components and in the production of a pulp that gave saccharification yields of 80 and 65% in 8 h for bagasse and wheat straw, respectively. By comparison, alkali steaming at 200°C (1.72 MPa) for 5 min gave saccharification yields of only 58 and 52% in 48 h. The increase in temperature from 140 to 200°C resulted in a gradual increase inin vitroorganic matter digestibility (IVOMD) for both the substrates. Also, the extent of alkalinity during pretreatment appears to effect the reactivity of the final product towards enzymes. Pretreatment times ranging from 5 to 60 caused a progressive decline in the IVOMD of bagasse and wheat straw by the alkali explosion method and this was accompanied by a progressive decrease in pH values after explosion. In the alkali‐steaming method, pretreatment time had no apparent effect with either substrate. An analysis of the alkali‐exploded products showed that substantial amounts of hemicellulose and a small proportion of the lignin were solubilized. The percentage crystallinity of the cellulose did not alter in either substrate but there was a substantial reduction in the degree of polymerization. The superiority of the alkali‐explosion pretreatment is attributed to the efficacy of fiber separation and disintegration; this increases the surface area and reduces the degree of poly

ISSN:0006-3592    

DOI:10.1002/bit.260280403

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis article presents a method for determining the rate constant for deactivation and the internal distribution of immobilized enzyme. This method makes use of the parallel deactivation process in a diffusion‐controlled regime, in which the internal activity profile behaves like a penetration front. This front basicallytracesthrough the initial active enzymatic profile, and one can determine the internal profile and the rate constant for deactivation from the experimentally observable bulk concentration versus time. This method is applied to the experimental data of the system of hydrogen‐peroxide‐immobilized catalase on controlled pore glass and Si–Al pa

ISSN:0006-3592    

DOI:10.1002/bit.260280404

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

年代:1986

数据来源: WILEY

摘要:

AbstractAn integrated microprocessor‐based fermenter controller was developed in 1980 for an operational environment at Cetus Corp. The main goals in the design and construction of the system were (1) to facilitate scale‐up; (2) to provide flexibility and high performance for optimizing fermentation processes; and (3) to be cost‐effective for 15 in‐house systems. It was also developed to work in conjunction with a laboratory minicomputer for on‐line optimization experiments. The controller controls temperature, agitation, dissolved oxygen, pH, and foam throughout each fermentation run without manual intervention. The feedback control parameters have been optimized to provide very accurate control over a wide range of setpoint conditions and under rapidly changing metabolic conditions such as induced during anEscherichia colibatch run. The controller has also been configured to monitor, display, and record each of the controlled variables; support the interactive operator console; and communicate with the laboratory computer. In over 4 years of operation, these systems have met the design goals and have proven to be very reliable. The controller is described, its operational performance presented, and a typical fermentation run d

ISSN:0006-3592    

DOI:10.1002/bit.260280405

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe activities of cellulases and xylanase were determined in laboratory cultures ofAspergillus terreusF‐413 performed on natural and chemically or hydrothermally pretreated oak sawdust. The best stimulation effects were obtained in the cultures containing sawdust treated with dioxane, sodium hydroxide, or phosphoric acid. Moreover, the sawdust pretreatment distinctly affected its enzymatic hydrolysis, especially when the preparation of hydrolase complex was isolated from the culture ofA. terreusF‐413 growing on the modified sawdust as a sole carbon source. The highest saccharification effect was observed when the sawdust was treated with dioxane, sodium hydroxide, or phosphoric acid. Glucose was the main product of sawdust decomposition found in the hydrolyza

ISSN:0006-3592    

DOI:10.1002/bit.260280406

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe thermal inactivation of a great number of immobilized enzymes shows a biphasic kinetics, which distinctly differs from the first‐order inactivation kinetics of the corresponding soluble enzymes. As shown for α‐amylase, chymotrypsin, and trypsin covalently bound to silica, polystyrene, or polyacrylamide, the dependence of the remaining activities on the heating time can be well described by the sum of two exponential terms. To interpret this mathematical model function, the catalytic properties of immobilized enzymes (number of active sites in silica‐bound trypsin,KMandEavalues in silica‐bound α‐amylase and chymotrypsin) at different stages of inactivation and the influence of various factors (coupling conditions, addition of denaturants or stabilizers, etc.) on the thermal inactivation of silica‐bound α‐amylase were studied. Furthermore, conformational alterations in the thermal denaturation of spin‐labeled soluble and silica‐bound β‐amylase were compared by electron spin resonance (ESR) studies. The results suggest that the biphasic inactivation kinetics reflects two different pathways according to which catalytically identical enzyme molecules are pr

ISSN:0006-3592    

DOI:10.1002/bit.260280407

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe technology of coupling ultrafiltration and fermentation has been tested with the acetonobutylic fermentation in continuous mode. The device developed was sterilizable by steam and permitted drastic cleaning of the ultrafiltration (UF) membrane without interrupting the continuous fermentation. It has been shown to be an easily operated and reliable experimental tool for studying high‐cell‐density cultures and inhibition phenomena. With total recycle of biomass, a dry weight concentration of 125 g/L was attained, which greatly enhanced the volumetric solvent productivity of acetonobutylic fermentation in averaging 4. 5 g/L h for significant periods of time (>70 h) and maintaining solvent concentration and yield at acceptable lev

ISSN:0006-3592    

DOI:10.1002/bit.260280408

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

年代:1986

数据来源: WILEY

摘要:

AbstractPerstraction (membrane‐aided solvent extraction) was utilized for elimination of ethanol inhibition in continuous ethanol fermentation using high sugar concentrate. Hollow fibers for an artificial kidney were used as a permeable membrane, and their capacity to extract ethanol was examined by using several organic solvents. When tri‐n‐butylphosphate was used as an extractant, a 500 g/L feed glucose medium was successfully fermented by immobilized yeast cells. During this continuous fermentation a high ehtanol productivity of 48 g/h‐L‐gel was held, and the solvent requirement per consumed glucose was 6 L‐solvent

ISSN:0006-3592    

DOI:10.1002/bit.260280409

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

年代:1986

数据来源: WILEY

摘要:

AbstractAs a part of the development of an integral mathematical model describing the up‐flow anaerobic sludge blanket (UASB) reactor, the kinetics of the conversion of organic wastes has to be known. We compared the Monod model with the model proposed by Andrews et al. Together with the assumption that the substrate for the anaerobic bacteria is formed by nonionized, volatile fatty acids, the Andrews model is able to describe substrate inhibition and reactor failure due to pH changes.From four batch experiments, with different concentrations of microorganisms, it could be concluded with a reliability of over 95% that the monod model was inadequate and Andrews' model was adequate to describe the measurements. Standard statistical techniques like theX2‐and theF‐test were used for this purpose.From a parameter sensitivity analysis for the Andrews model it followed that the maximum specific growth rate μ Amaxof the bacteria and the inhibition constantK1are the parameters which influence the system most. Thus, these parameter were determined experimentally and most accurately. The results are:\documentclass{article}\pagestyle{empty}\begin{document}$$\mu^{A}_{\max} = 16*10^{-4}{\rm h}^{-1}\pm 2\%\quad {\rm and}\quad K_l = 0.0158\,{\rm g}\,{\rm HAc/L}\pm 2.5\%$$\end{document}The other parameters were taken from literature. From calculation of the Thiele modulus for the particles it follows that transport limitation of the substrate in the flocus is not significant. The efficiency η is 0.85 in the w

ISSN:0006-3592    

DOI:10.1002/bit.260280410

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

年代:1986

数据来源: WILEY

摘要:

AbstractXylose transport, xylose reductase, and xylitol dehydrogenase activities are demonstrated inSaccharomyces cerevisiae.The enzymes in the xylose catabolic pathway necessary for the conversion of xylose to xylulose are present, althoughS. cerevisiaecannot grow on xylose as a sole carbon source. Xylose transport is less efficient than glucose transport, and its rate is dependent upon aeration. Xylose reductase appears to be a xylose inducible enzyme and xylitol dehydrogenase activity is constitutive, although both are repressed by glucose. Both xylose reductase and xylitol dehydrogenase activities are five– to tenfold lower inS. cerevisiaeas compared toCandida utilis.In vivoconversion of14C‐xylose inS. cerevisiaeis demonstrated and xylitol is detected, although no significant levels of any other14C‐labeled metabolites (e. g., ethanol) are obs

ISSN:0006-3592    

DOI:10.1002/bit.260280411

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

年代:1986

数据来源: WILEY