摘要:

AbstractThe relationship among extent of hydrolysis, reaction time, and enzyme dosage was investigated. For this, Sigmacell 50 and pretreated poplar wood (20 g/L) was hydrolyzed with varying dosages of cellulases from three different sources (5 to 100 FPU/g) for time periods ranging from 2 to 94 h. It was found that the formation of glucose can be described by summation of two parallel first order reactions. The extent of hydrolysis at fixed time increases with increasing enzyme dosage in a hyperbolic function. From the empirical data it is possible to calculate the fractions of easily and difficult hydrolyzable cellulose and the digestability which could maximally be obtained at infinite enzyme loadings. In the system Sigmacell 50 and Celluclast the easily and difficult hydrolyzable components are 43.0 and 57.0%, respectively, and the maximum digestability at 94 h is 82.6%. Poplar wood, steam treated at 200°, 220°, and 240°C, showed with Celluclast at 24 h a maximum digestability (weight percentage of wood degraded to glucose) of 43.9, 64.9, and 68.0%. The relationships derived from experimental data allow one to compare objectively the effectiveness of different cellulase enzymes and different pretreatmen

ISSN:0006-3592    

DOI:10.1002/bit.260331002

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

年代:1989

数据来源: WILEY

摘要:

AbstractTwo human squamous carcinoma cell lines and human diploid fibroblasts were examined for the production of extracellular matrix (ECM) molecules including fibronectin (FN), laminin (LN), and thrombospondin (TSP) when grown on a number of different substrates. The substrates used included glass, plastic, collagen (gelatin), and DEAE‐dextran. Levels of TSP as indicated by enzyme‐linked immunosorbent assay did not vary significantly as a function of substrate. In contrast, LN levels in the culture medium were significantly decreased when the cells were grown on DEAE‐dextran or collagen‐linked dextran as compared to the other substrates. FN levels were slightly lower in the culture medium of the cells grown on DEAE‐dextran. Biosynthetic labeling followed by immunoprecipitation indicated that the reduction in LN was due, in part, to decreased biosynthesis. Previous studies have indicated that LN influences the behavior of epithelial cells in culture and that the cells, themselves, are a major source of the LN. The differences in LN production noted here indicate that the production of this ECM component is influenced by the substratum on which the cells are grown. These differences could contribute to alterations in biological properties that are known to be influenced by the s

ISSN:0006-3592    

DOI:10.1002/bit.260331003

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe influence of the composition of the growth medium on the production of endo‐1,4‐β‐D‐glucanase (CM‐cellulase) activity byP. pinophilumwas studied in shake flask cultures using Avicel PH101 as the carbon source. It was observed that the culture conditions had a profound effect on the level of endoglucanase (CM‐cellulase) produced byP. pinophilum.However, isoelectric focusing of the endoglucanase activity obtained from shake flask and fermenter cultures using the same growth medium revealed that the enzyme system found in both cultures was identical qualitatively, and contained seven or eight different endoglucanase components. All the endoglucanase components appeared simultaneously in the early stages of culture and prolonged incubation resulted only in an increase in the concentration of these enzymes. Protease levels were found to be low in both types of culture but were particularly so in the growth medium which contained corn steep liquor. The proteases were unable to release low molecular weight peptides whenP. pinophilumcellulase protein was used as a substrate. The results were interpreted to indicate that the multiplicity of endoglucanase components found in cultures ofP. pinophilumis most likely the result of expression of a number of specific genes rather than by post‐secretional modification of one or more endoglucanase(s) synthesized

ISSN:0006-3592    

DOI:10.1002/bit.260331004

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

年代:1989

数据来源: WILEY

摘要:

Abstractβ‐galactosidase fromAspergillus Oryzaeimmobilized in a spiral flow reactor was used to effect the hydrolysis of the lactose component of skim milk. Residence time distribution measurements were used to assess the amount of longitudinal dispersion occurring as a consequence of the spiral flow pattern and the semiporous nature of the polymeric material used to construct the spiral. It was possible to model the flow conditions as tubular flow with a Peclet number that was a linear function of the reactor space time. Nonlinear regression methods were used to determine the kinetic parameters of three proposed enzymatic rate expressions. The best fit of the data was obtained using a rate expression containing separate terms for competitive inhibition of the reaction by both the a and β anomers of galactose. This kinetic model also incorporates the kinetics of the mutarotation between these forms. At 30°C and a space time of 7 minutes, 80% of the lactose present in skim milk can be converted to glucose and galac

ISSN:0006-3592    

DOI:10.1002/bit.260331005

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

年代:1989

数据来源: WILEY

摘要:

AbstractEndo‐polygalacturonase (endo‐PG) was immobilized on a wide range of natural and synthetic macromolecular supports and their modified derivatives representing many chemical classes, including esters, amides, phenols, alkyl‐ and arylamines, and carboxyl derivatives. The immobilization entailed methods of adsorption alone as well as covalent bond formation using glutaraldehyde or carbodiimide or via the diazo‐coupling reaction. The most promising system proved to be immobilization on trimalehylchitosan (TMC) via adsorption followed by treatment with glutaraldehyde (GA). The binding capacity of the support is on the order of 13,000 IU/g, half of which is active. Various properties of immobilized endo‐PG were evaluated. The optimum pH of the enzyme shifted to the alkaline side. The relative catalytic activity was considerably high even at room temperature and remained so above 70°C. The thermal stability at pH 3‐4 was notably improved by immobilization, the half‐time doubling. Finally, the apparentKmwas greater for immobilized endo‐PG than for native enzyme, while theVmaxwas smaller for the im

ISSN:0006-3592    

DOI:10.1002/bit.260331006

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

年代:1989

数据来源: WILEY

摘要:

AbstractReversible competitive inhibitors of the three enzymes β‐galactosidase, trypsin, and serum cholinesterase have been covalently attached to nonionic ethoxylated surfactants. The binding of the resulting affinity‐derivatized surfactants to the respective enzymes has been quantified by measuring Michaelis‐Menten inhibition constants with kinetic assays. The surfactant‐inhibitor of serum cholinesterase, octaethylene glycol monohexadecy ether pyridinium (C16E8‐PYR), was adsorbed in aqueous solution to an octadecyl‐bonded reverse‐phase silica packing in a 2 × 0.2 cm stainless steel test column. The ability of the test column to function as a high‐performance affinity chromatography (HPAC) column was determined by applying a mixture of bovine serum albumin and cholinesterase (4:1 w/w). Virtually all of the cholinesterase bound and was eluted by applying a gradient in ionic strength. The applied cholinfesterase was recovered with a yield of over 90% and an 11‐fold purification. An aliquot of raw horse serum was then purified in the same fashion with a yield of 84% and a 280‐fold purification. The surfactant‐inhibitor was easily removed from the column with an alcohol wash for sterilization, cleaning, or application of a different affinity ligand. Moreover, the ligand density on the column can be easily manipulated by adsorbing mixtures of derivatized and underivatized surfactants. Leakage of ligands from the support seems to be minimal since the cholinesterase affinity column was operated efficiently after being exposed to 24,000 column volumes of buffer. The application of this technique to high‐capacity, high‐throughput reversible affinity purifications is limited only by the ability t

ISSN:0006-3592    

DOI:10.1002/bit.260331007

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

年代:1989

数据来源: WILEY

摘要:

AbstractTrypsin and α‐chymotrypsin were immobilized by gelentrapment in polyacrylamide cross‐linked withN,N1‐methylenebisacrylamide. The immobilized enzymes are catalytically efficient in suspensions of reverse micelles formed in isooctane by bis(2‐ethylhexyl) sodium sulfosuccinate (AOT) and water. Both entrapped enzymes are stable in reverse micellar suspension at room temperature and pH 8.2 for 3 days and lose 30‐40% activity after 1 week. The enzymes obey Michaelis‐Menten kinetics in the investigated concentration range withKmvalues higher than those in solution. Activity of the enzymes is independent of the water content of the micellar solution. No shift in pH optimum was observed for immobilized trypsin activity towardNα‐benzoyl‐L‐arginine ethyl ester. The utility of the procedure, which combines the advantage of enzyme immobilization and enzymology in reverse micelles, is illustrated by an example of peptide synthesis. In particular, peptide synthesis (e. g., ZAlaPheLeuNH2) using water‐insoluble substrate has been performed with gelentrapped α‐chymotrypsin in reverse micellar suspension with the advanta

ISSN:0006-3592    

DOI:10.1002/bit.260331008

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

年代:1989

数据来源: WILEY

摘要:

AbstractFermentation rates and intracellular compositions have been determined for alginate‐entrappedSaccharomyces cerevisiaeand for identical cells in suspension. Glucose uptake and ethanol and glycerol production are approximately two times faster in immobilized cells than in suspended cells. Phosphorus‐31 nuclear magnetic resonance (NMR) spectroscopy of fermenting immobilized and suspended cells shows differences in intermediate metabolite levels such as fructose‐1,6 diphosphate, glucose‐6‐phosphate, and 3‐phosphoglycerate and in internal pH. Carbon‐13 NMR shows an increase in polysaccharide production. These data suggest that immobilization has accelerated the rate of glucose transport or of glucose phosphorylation. These effects of immobilization upon cell metabolism are observed in a very short period of time under conditions in which negligible DNA, RNA, or protein synthesi

ISSN:0006-3592    

DOI:10.1002/bit.260331009

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe electrical impedance of the culture medium shows complex changes during the growth and fermentation process of yeast, and this prevents its possible application for the monitoring of certain yeast activities. Clarification of the mechanism of such changes is thus essential for practical use. As a first step toward this aim, the impedance, yeast concentration, and pH of a batch culture medium were measured using special cells with two compartments and also the usual type of cell with one compartment. In the special cells, the yeast was cultured in one compartment only. Conducting ions and nonconducting substances diffused through an intermediate porous membrane sandwiched between the two compartments. The impedances of the two compartments were measured simultaneously by the four‐electrode method. The main mechanism responsible for increasing the impedance was the conducting ions produced by the yeast extract added as a nutrient to the culture broth by certain nonconducting substances during the process of growth. The increase in the yeast concentration was also a minor factor increasing the impedance. These increases surpassed the impedance decrease caused by the increase of H+ions produced by some accumulated acidic substances, and the impedance thus increase

ISSN:0006-3592    

DOI:10.1002/bit.260331010

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe design and application of a settler to a continuous fermentation process with yeast recycle were studied. The compact lamella‐type settler was chosen to avoid large volumes associated with conventional settling tanks. A rationale of the design method is covered. The sedimentation area was determined by classical batch settling rate tests and sedimentation capacity calculation. Limitations on the residence time of the microorganisms in the settler, rather than sludge thickening considerations, was the approach employed for volume calculation. Fermentation rate tests with yeast after different sedimentation periods were carried out to define a suitable residence time. Continuous cell recycle fermentation runs, performed with the old and new sedimentation devices, show that lamella settler improves biomass recycling efficiency, being the process able to operate at higher sugar concentrations and faster dilution rate

ISSN:0006-3592    

DOI:10.1002/bit.260331011

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

年代:1989

数据来源: WILEY