摘要:

AbstractThis article presents a review of the enzyme mechanisms involved in degradation of cellulose by the white‐rot fungusSporotrichum poulverulentum. The hydrolytic enzymes involved include: (1) five endo‐1,4‐β‐glucanases; (2) one exo‐1,4‐β‐glucanase, and (3) one or several 1,4‐β‐glucosidases. A recently discovered oxidative enzyme of importance inin vitrocellulose degradation seems to be a cellobiose oxidase. An oxidoreductase, cellobiose:quinone oxidoreductase, is of importance both in cellulose and in lignin degradation. Regulatory mechanisms of the extracellular enzyme activities, such as monosugar levels causing catabolite repression of the endoglucanases, have also been investigated. The enzymes used byS. pulverulentumin cellulose hydrolysis are compared to those used byTrichoderma viride. Very similar types of enzymes are used in both cases. However, no oxidative enzyme has so far been found to be involved in extracellular cellulose degradation in the case ofT. viride. Recommendations for furthe

ISSN:0006-3592    

DOI:10.1002/bit.260200302

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

年代:1978

数据来源: WILEY

摘要:

AbstractMethanol oxidase produced by the yeastHansenula polymorphaDL‐1 was used for the enzymatic oxidation of methanol to formaldehyde. The kinetics of enzyme and protein release during cell desruption were studied at the laboratory scale with a Braun homogenizer and the pilot plant scale with a Manton–Gaulin homogenizer. Conditions were defined for maximum release and retention of high activity in cell‐free extracts. Methanol oxidase was immobilized by adsorption on DEAE‐cellulose from enzymes in cell‐free extracts or from ammonium sulfate purified purified fractions. The kinetics of formaldehyde formation with both soluble and immobilized enzyme was studied in batch and continuous

ISSN:0006-3592    

DOI:10.1002/bit.260200303

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

年代:1978

数据来源: WILEY

摘要:

AbstractThis paper describes a mathematical model of the lag phases ofSaccharomyces cerevisiaethat incorporates the basic concepts previously presented in a two‐stage deterministic model for the growth of this organism under conditions of oxygen excess with a sugar as the growth‐limiting substrate. The model structure was suggested by an extensive investigation of the causes of the lag phases ofS. cerevisiaewhich found that, in contrast to the traditionally accepted trends, the length of the lag phase was not inoculum‐size dependent. This was consistent with other previously published work which suggested that a major factor in the length of the lag phases inS. cerevisiaewas the need to synthesize adequate levels of glycolytic and respiratory enzymes. These suggestions were confirmed experimentally with lag‐age data. Based on this conclusion a mathematical model was developed incorporating a description of the levels of glycolytic and respiratory enzymes and their effect on the growth rate and metabolism. This model was tested experimentally and the initial results indicate indicate that many aspects of the lag phase of this organism may be described mathematically. The experimental findings further support the concept of primary regulatory control proposed by Bijkerk a

ISSN:0006-3592    

DOI:10.1002/bit.260200304

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

年代:1978

数据来源: WILEY

摘要:

AbstractImmobilized soybean β‐amylase was prepared by using porous cellulose beads. The expressed activity of the β‐amylase–cellulose beads conjugated below 35 mesh was 59–69% of the initial activity and the protein content was 10–13%. General properties of the conjugate were almost identical with those of the native enzyme except for theKmvalue. TheKmvalue of the conjugate was 40mMand theKmvalue of the native enzyme was 0.6mM. This large difference was probably caused by pore structure, i.e., a pore diffusion problem. The film diffusion problem occurred at the flow rate below a linear velocity of 3 cm/min. Maximum maltose contents of the hydrolyzates prepared by the conjugate and the native enzyme were 69 and 71%, respectively. After a continuous column operation at 50°C for 17 days, the activity of the column was 60% of the activity. The half‐life of the column at 40

ISSN:0006-3592    

DOI:10.1002/bit.260200305

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

年代:1978

数据来源: WILEY

摘要:

AbstractGraphites of different manufacture and origin exert positive but different accelerations on the rate of oxidation of NADH to NAD+in aqueous solution; different proportions of the oxidized form of NAD retain enzymatic activity depending on the nature of the graphite. Oxidative pretreatment of the graphite surfaces increases the rates of NADH oxidation, but subsequent silanization of the surfaces to attach alkylamine groups causes the rates to decrease. The experimental results suggest the presence of at least two types of sites on graphite surfaces: One very reactive site which produces a high percentage of an enzymatically inactive reaction product of NADH and is itself deactivated during the course of reaction, and another type of site which promotes the oxidation of NADH to enzymatically active NAD+in high yields.

ISSN:0006-3592    

DOI:10.1002/bit.260200306

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

年代:1978

数据来源: WILEY

摘要:

AbstractFormaldehyde, an intermediate in methanol oxidation, plays an important role in controlling methanol utilization by microorganisms which fix carbon via the ribulose monophosphate (RMP) cycle. The extracellular formaldehyde concentration profiles in batch cultures at low and high starting methanol concentrations with and without the presence of semicarbazide in the media, suggest the role played by formaldehyde. The impact of formaldehyde on growth is demonstrated by the time dependent and the initial methanol concentration‐dependent cell‐mass‐yield coefficient. Kinetic studies of the enzymes involved in the oxidation and incorporation of C1units suggest that enzyme inhibition cannot account for the observed growth inhibition. A mechanism is proposed to explain methanol and formaldehyde utilization that stresses the transcriptional regulation of mass flow around formaldehyde in assimilation and oxidation pathways through repression and indu

ISSN:0006-3592    

DOI:10.1002/bit.260200307

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

年代:1978

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260200308

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

年代:1978

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260200309

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

年代:1978

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260200310

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

年代:1978

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260200311

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

年代:1978

数据来源: WILEY