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Query: UMLS:C0040822 (tremor)
 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two forms of cellulase, buffer soluble (BS) and buffer insoluble (BI), are induced as a result of auxin treatment of dark-grown pea epicotyls. These two cellulases have been purified to homogeneity. Antibodies raised against the purified cellulases were conjugated with ferritin and were used to localize the two cellulases. Tissue sections were fixed in cold paraformaldehyde-glutaraldehyde and incubated for 1 h in the ferritin conjugates. The sections were washed with continuous shaking for 18 h and subsequently postfixed in osmium tetroxide. Tissue incubated in unconjugated ferritin was used as a control. A major part of BI cellulase is localized at the inner surface of the cell wall in close association with microfibrils. BS cellulase is localized mainly within the distended endoplasmic reticulum. Gogli complex and plasma membrane appear to be completely devoid of any cellulase activity. These observations are consistent with cytochemical localization and biochemical data on the distribution of these two cellulases among various cell and membrane fractions.
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PMID:Subcellular localization of cellulases in auxin-treated pea. 76 48

Propagules of Rhizoctonia solani grown in modified Czapek's medium containing sodium polypectate or carboxymethyl cellulose as a sole carbon source produced both extracellular and cell-bound polygalacturonase (PG), and cellulase (Cx), respectively. The cell-bound enzymes can be released to various extents by shaking the germinating propagules in solutions of NaCl, KCl, phosphate buffer, Na2EDTA (ethylenediaminetetraacetate), detergents such as Triton X-100 (octyl phenoxypolyethoxyethanol), Tween 80 (polyoxyethylene sorbitan monooleate), Celmusol, and distilled water. Sodium dodecyl sulfate (SDS) inactivated both PG and Cx but did no affect Cx activity in phosphate buffer solution. PG was more easily released by salts from the mycelium of R. solani than Cx. The release of both enzymes was a passive process and was not due to an osmotic effect. The amount of the cell-bound fraction was correlated with the total amount of the extracellular fraction rather than with the mycelial growth. At least one-third of the cell-bound fractions of both enzymes was found to be associated with the cell wall fraction of the mycelium.
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PMID:Release of cell-bound polygalacturonase and cellulase from mycelium of Rhizoctonia solani. 80 41

Enzyme stability studies in case of Sclerotium rolfsii UV-8 mutant have been investigated under the conditions used for saccharification of cellulose (50 degrees C, pH 4.5, 48 h). Avicelase (measure of exoenzymes) and xylanase were found to be less stable than CMCase (endoglucanase) and beta-glucosidase. Merthiolate (and other Hg compounds) added as a biocide, inactivated avicelase and xylanase about 60-70%. Of the antibiotics tested, tetracycline, chloramphenicol, and streptomycin sulfate were found suitable as an additive in cellulose hydrolysis system. The optimum hydrolysis of alkali-treated (AT)-rice straw, AT-bagasse, Solka Floc SW40, and Avicel P.H.101 was observed under shaking conditions at pH 4.5, 50 degrees C in CO2 atmosphere. It is suggested, all the studied parameters could be used for the evaluation of mutant strains.
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PMID:Factors affecting stability of Sclerotium rolfsii UV-8 mutant cellulase complex under saccharification conditions. 179 12

Enzyme stability studies have been reinvestigated under the conditions used for cellulose hydrolysis (pH 4.8, 50 degrees C, 24 hr). The cellobiohydrolase (CBH) component as measured on Avicel is less stable than other enzymes of the cellulase complex, and is 60% inactivated by merthiolate (and other Hg compounds) under the above conditions. Endo-beta-1,4-glucanase is much more stable, and more resistant to merthiolate and other compounds. Under unshaken conditions the Avicelase of the Rutgers strain C 30 shows greater stability to heat than that of other available strains. Biocides must be selected not only for their ability to prevent contamination, but also for their compatibility with cellulases. Tetracycline and chlortetracycline are inexpensive, effective in very low concentrations, have no harmful effect on the enzymes, and are compatible with the yeasts that subsequently grow on the sugar solutions to produce alcohol. Attempts have been made to stabilize the enzymes by chemical modification in such a way as to maintain their solubility. Glutaraldehyde treatment greatly increased the enzyme size, lowered the pI values, and gave a slight shift in the pH activity curve. There was, unfortunately, no increase in enzyme stability, and the activity of enzymes on solid celluloses was adversely affected. Shaking greatly reduced the hydrolysis of Avicel by Trichoderma reesei C 30 enzyme. The adverse effect was accompanied by a decrease in recoverable enzyme and protein.
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PMID:Stability of the cellulase of Trichoderma reesei under use conditions. 676 32

The ability to produce cellulose and xylan degrading enzymes by different strains of Thecotheus pelletieri, in liquid synthetic media with cellulose and xylan as inducers, was compared. All the strains tested were able to grow and produce cellulases and xylanases, being the strain BAFC 2077 the best producer. Several cultural conditions were analysed in order to optimise enzyme production by strain 2077. Shaking cultures gave higher yields of cellulases and xylanases compared with stationary ones. Asparagine at 0.75 g N/L was the best nitrogen source in promoting enzyme production. The influence of different surfactants on enzyme production was studied. Tween 80 exhibited no effect on growth and enzyme production, whereas Tween 20 and Triton X-100 were inhibitory. By means of studies of variation of cellulose/xylan ratio in the culture medium we determined that cellulose and xylan induced cellulase and xylanase synthesis, being the specific substrates the most effective. The inducible behavior of cellulases and xylanases in T. pelletieri was determined by means of inhibition of protein synthesis by cycloheximide and ethidium bromide. Moreover, we found that glucose as well as xylose repressed cellulase and xylanase synthesis in T. pelletieri.
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PMID:Cellulose and xylan degrading enzymes in Thecotheus pelletieri. 1114 50

In an attempt to elucidate the effect of mixing on the rate and extent of enzymatic hydrolysis of cellulosic substrates, alpha-cellulose was hydrolysed using a commercial cellulase preparation at varying levels of substrate concentration (2.5,5 and 7.5% (w/v)) and by using three shaking regimes: continuous at low-speed (25 rpm), continuous at high-speed (150 rpm) and an intermittent regime comprised of high and low-speed shaking intervals. The continuous, high-speed shaking produced the highest conversion yields, whereas the intermittent and low-speed shaking regimes resulted in lower conversions. After 72 h, at all shaking regimes (150 rpm,25 rpm and intermittent), using a low substrate concentration (2.5%) produced conversion yields (82,79 and 80%) higher than those obtained at high (7.5%) substrate concentration (68,63 and 68%). As the substrate concentration increased, the conversion yields at intermittent shaking gradually approached those resulting from high-speed shaking. Thus, it appears that intermittent shaking could be a beneficial process option as it can reduce the mixing energy requirements while producing reasonably high conversion yields.
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PMID:The effect of shaking regime on the rate and extent of enzymatic hydrolysis of cellulose. 1140 53

The efficient saccharification of lignocellulosic materials requires the cooperative actions of different cellulase enzyme activities: exoglucanase, endoglucanase, beta-glucosidase, and xylanase. Previous studies with the fungi strains Aureobasidium sp. CHTE-18, Penicillium sp. CH-TE-001, and Aspergillus terreus CH-TE-013, selected mainly because of their different cellulolytic and xylanolytic activities, have demonstrated the capacity of culture filtrates of cross-synergistic action in the saccharification of native sugarcane bagasse pith. In an attempt to improve the enzymatic hydrolysis of different cellulosic materials, we investigated a coculture fermentation with two of these strains to enhance the production of cellulases and xylanases. The 48-h batch experimental results showed that the mixed culture of Penicillium sp. CH-TE-001 and A. terreus CH-TE-013 produced culture filtrates with high protein content, cellulase (mainly beta-glucosidase), and xylanase activities compared with the individual culture of each strain. The same culture conditions were used in a simple medium with mineral salts, corn syrup liquor, and sugarcane bagasse pith as the sole carbon source with moderate shaking at 29 degrees C. Finally, we compared the effect of the cell-free culture filtrates obtained from the mixed and single fermentations on the saccharification of different kinds of cellulosic materials.
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PMID:Mixed submerged fermentation with two filamentous fungi for cellulolytic and xylanolytic enzyme production. 1201 34

In an attempt to elucidate the effect of reduced mixing on the enzymatic hydrolysis of lignocellulosic feedstocks, a pretreated softwood substrate was hydrolyzed under various mixing regimes using a commercial cellulase mixture. The substrate was generated by SO2-catalyzed steam explosion of Douglas fir wood chips followed by alkali-peroxide treatment to remove lignin. Three mixing regimes were tested; continuous mixing at low (25 rpm) and high (150 rpm) speeds, and mixing at low-speed interspersed with 5-min intervals of high-speed agitation at 150 rpm. At both substrate concentrations (7.5 and 10% [w/w]), the mixed-speed mixing was able to produce sufficiently high conversion rates and yields (93% after 96 h), close or slightly better than those obtained under vigorous mixing (150 rpm). The low-speed shaking produced appreciably lower conversion yields at both levels of substrate concentration. Therefore, the mixed-speed regime may be a viable process option, because it does not seem to have an adverse impact on the cellulose conversion yield and can be an effective means of reducing the mixing energy requirements of an enzymatic hydrolysis process.
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PMID:Influence of mixing regime on enzymatic saccharification of steam-exploded softwood chips. 1201 72

The mycelia of Trichoderma reesei Rut C30 were adsorbed and immobilized within the porous polyurethane supporter. It was found that the synthesis of cellulase by the immobilized cells and the enzymatic hydrolysis of corn stover were able to be carried out in a nitrogen source-limiting medium. Under repeated batch processes with 60 g/L corn stover pretreated by 2% NaOH at 85 degrees C, the average cellulase activity (FPA) was 0.70 IU/ml, the concentration and yield of the reducing sugar were 26.41 g/L and 89.11% respectively after shaking culture at 150 r/min, 30 degrees C, pH 4.8 for 108 h. Total of 12 repeated batches were performed in 54 days. The immobilized cells kept the weight around 10 g/L. The fed-batch process was also studied with the same immobilized cells. Total of 120 g/L corn stover was added in different feeding manners. The reducing sugar of 52.8 g/L was produced after 7 days and the saccharification efficiency (89.2%) was almost the same as the batch process. The results indicated that the cellulase production and cellulosic material saccharification in situs by the immobilized Trichoderma reesei cells is an convenient and effective process for conversion and utilization of renewable biomass.
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PMID:[Saccharification of corn stover by immobilized Trichoderma reesei cells]. 1254 71

An Aspergillus giganteus strain was isolated as an excellent producer of xylanase associated with low levels of cellulase. Optimal xylanase production was obtained in liquid Vogel medium containing xylan as carbon source, pH 6.5 to 7.0, at 25 degrees C and under shaking at 120 rpm during 84 h. Among the several carbon sources tested, higher xylanase production was verified in xylan, xylose, sugar-cane bagasse, wheat bran and corn cob cultures, respectively. Optimal conditions for activity determination were 50 degrees C and pH 6.0. The xylanolytic complex of A. giganteus showed low thermal stability with T(50) of 2 h, 13 min and 1 min when it was incubated at 40, 50 and 60 degrees C, respectively, and high stability from pH 4.5 to 10.5, with the best interval between 7.0 to 7.5. This broad range of stability in alkali pH indicates a potential applicability in some industrial processes, which require such condition. Xylanolytic activity of A. giganteus was totally inhibited by Hg(+2), Cu(+2) and SDS at 10 mM. The analysis of the products from the oat spelts xylan hydrolysis through thin-layer chromatography indicated endoxylanase activity, lack of debranching enzymes and beta-xylosidase activity in assay conditions.
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PMID:Xylanolytic complex from Aspergillus giganteus: production and characterization. 1287 8


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