Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cellulases”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed1991

Characterization of the leader peptide of an endo-type cellulase produced by an alkalophilic Streptomyces strain.

An endo-type semi-alkaline cellulase (CMCase I) produced by an alkalophilic Streptomyces strain has an extraordinarily long leader peptide of about 70 amino acids (aa), which can be grouped into four distinct regions, an NH2-terminal region (13 aa), an Arg-cluster region (13 aa), a hydrophobic region (23 aa), and an Ala/Pro-repeat region (12 aa). For identification of the function of each part of the leader peptide for secretion of the enzyme, mutation in the leader peptide were generated by site-directed mutagenesis using the cloned gene, and the mutant genes were expressed in a cellulase-negative mutant strain, Streptomyces lividans HN1. Although all the alterations in the leader peptide, except for one case, decreased secretion to various extents, in S. lividans, the following conclusions were obtained. Comparison of the intra- and extra-cellular enzyme activities of the mutants suggested that the Arg-cluster region was essential in secretion of the cellulase. Deletion of 8 amino acids rich in threonine and proline in the NH2-terminal region enhanced the secretion to a small extent. Deletion of the Ala/Pro repeat region had almost no effect on secretion.

Amino Acid Sequence↗
PubMed2005

Cellulase production by Trichoderma reesei using sawdust hydrolysate.

Sawdust hydrolysates were investigated for their ability to support cell growth and cellulase production, and for potential inhibition of Trichoderma reesei Rut C30. Simultaneous fermentations were conducted to compare the hydrolysate-based media with the controls having equivalent concentrations of glucose and Avicel cellulose. Six hydrolysates differing in the boiling durations in the hydrolysis procedure were evaluated. The hydrolysates were found to support cell growth and induce active cellulase synthesis. The maximum specific cellulase production rate was 0.046 filter paper units (FPU)/(g of cells.h) in the hydrolysate-based systems, much higher than that (0.017 FPU/[g of cells.h]) in the controls.

Cell Culture Techniques↗
PubMedDate not supplied

[Constitutive synthesis of cellulase by Trichoderma lignorum].

The induction of cellulase synthesis by lactose was studied in the resting cells of Trichoderma lignorum OM 534. The effect depended on the concentration of lactose, pH, and the age of the mycelium. The induction of the enzyme synthesis by lactose is supressed by glucose and its metabolites. The repression by glucose is partly eliminated by Cyk 3'-5'-AMP, theophylline, and coffeine. The induction of cellulase by lactose is regarded as a derepression of the synthesis of this enzyme as a result of slow assimilation of the disaccharide. The synthesis of cellulase in T. lignorum is presumed to be constitutive.

Caffeine↗
PubMedDate not supplied

[Synthesis and secretion of the components of the cellulase complex in Aspergillus terreus].

Aspergillus terreus was found to have two functionally different cellobiases. One of them is excreted into the surrounding medium and is a part of the cellulase complex. The second one is an endocellular (or periplasmic) enzyme. It is distinguished by its stability, the time of mRNA operation, the sorption of cell debris; moreover, its activity does not depend on changes in the parameters of the medium when the incubation mixture is replaced and the surface is treated with 0.5 M NaCl. The synthesis of all components in the cellulase complex of A. terreus is coordinated. The time it takes the mRNAs for cellulases to function does not exceed 2 h. A close correlation exists between the synthesis and secretion of polysaccharases (endoglucanases and exoglucosidases) in A. terreus. Cellobiase is adsorbed by the fungal cell wall owing to charge interactions; its desorption depends on the ionic strength and the pH of the medium.

Aspergillus↗
PubMed1983

[Ability of cellulases to degrade crystalline cellulose as a result of their effective adsorption on the substrate: experimental confirmation and theoretical interpretation].

It was shown experimentally that the increase in the adsorption ability of cellulases leads to a sharp increase of the rate of the enzymatic degradation of crystalline cellulose. At the same time the rate of degradation of amorphous cellulose does not depend on the adsorption ability of cellulases. These effects have been explained using a model which takes into consideration the influence of the structure of the solid substrate on the surface mobility of the adsorbed molecules of the enzyme. The equations were derived which inter-relate the catalytic and the adsorptive properties of cellulases.

Adsorption↗
PubMedDate not supplied

[Effect of nitrogen sources on cellulase biosynthesis by a mutant strain of Trichoderma viride 44].

The effect of various nitrogen sources on cellulase biosynthesis by the mutant strain Trichoderma viride 44 was examined. This strain may utilized nitrogen in the nitrate, ammonium of organic form. When cultivating this strain, it appears advantageous to add to the nutrient medium yeast and yeast lyzates as well as their mixture with ammonium sulfate. Cellulase reached its maximum activity of 20.2, 21.5 and 23.2 mu/ml when grown on the medium containing ammonium phosphate, peptone and brewing yeast plus ammonium sulfate, respectively. It is useful to apply nitrogen in its organic forms in small quantities and in combination with mineral forms. The nitrogen presence in the medium is necessary only at the exponential stage of fungal growth. The lack of nitrogen in the stationary stage characterized by the maximum cellulase formation does not inhibit an increase in the enzyme activity.

Cellulase↗
PubMedDate not supplied

[Hydrolysis of cellulose by fungi. II. Production of cellulases by Trichoderma harzianum by fermentation in liquid media].

Microcristalline cellulose (cellulose Avicel, Merck) supported growth of Trichoderma harzianum and induced production of cellulases in liquid cultures. After 50 h growth, the total cellulasic activities present in both the supernatant and the mycelium were 3,000 IU/l of carboxymethyl cellulose, 400 IU/l of filter paper activity, and 4 IU/l of cotton activity corresponding to 1.7 g/l of proteins. Cellulase production could be increased by a preliminary treatment of cellulose, and pH regulation during growth. The influence of inoculum concentration was studied and an optimum of 3 x 10(7) conidia/g dry weight of substrate was demonstrated. Using a synthetic culture medium, a soluble factor of germination was demonstrated which could be leached out by 3 successive washings of conidia.

Cellulase↗
PubMed1977

Synthesis of cellulase by Fusarium sp. in different culture conditions.

The mechanism of the synthesis of cellulases by Fusarium sp. strain was studied. It was found that a significant role in determination of cellulases is played by the adsorption of these enzymes on cellulose. The aeration level of the culture media had a significant effect on the synthesis as well as on the enzymatic complexity of cellulases.

Air↗
PubMedDate not supplied

Cellulase activity, degradation of cellulose and lignin and humus formation by cellulolytic fungi.

Cellulase activity and degradation of cellulose and lignin in wheat straw and formation of humus during degradation by Botryotrichum sp., Masoniella sp., Paecilomyces fusisporus, Sclerotium sp. and Trichurus spiralis was studied. All the cultures exhibited carboxy-methyl-cellulase activity, but cellulase activity on cellulose powder, filter paper and cotton was shown only by Masoniella sp., P. fusisporus and Sclerotium sp. when grown on cellulose powder in submerged culture conditions. However, when grown on wheat straw in solid culture all fungi exhibited FPD activity. All except Masoniella sp. degraded both cellulose and lignin efficiently as compared to cellulose. There was formation of humus like substances during growth of fungi on wheat straw.

Carboxymethylcellulose Sodium↗
PubMed1993

Cellulase production on high levels of cellulose and corn steep liquor.

Several enhanced cellulase mutants of Trichoderma reesei have been used for cellulase production using corn steep liquor and microcrystalline cellulose as substrates. Under the optimum fermentation conditions on 6% cellulose and 3.6% corn steep liquor Trichoderma reesei Rut C 30 produced high levels of cellulase enzymes 6MC-ase 54 IU/ml, filter paper activity 3.2 IU/ml after 10 days incubation at 28-30 degrees C.

Ammonium Sulfate↗
PubMed1996

Transcriptional control of the cellulase genes in Trichoderma reesei.

The expression of the cellulase transcripts of Trichoderma reesei is controlled by the nature of the energy carbon sources used in the culture medium. Cellulose and the soluble disaccharide sophorose, but not glycerol or glucose, act as inducers. Evidence is presented suggesting that a low constitutive extracellular cellulolytic system catalyzes the formation of a soluble inducer from cellulose, and this inducer triggers the expression of the cellulase transcripts. This basal and cellulose-induced expression of the cellobiohydrolase I mRNAs (cbh1), the major member of the cellulase system, is transcriptionally controlled by two independent cis-acting DNA regions. In addition, expression of the cbh1 transcript is influenced by the physiological state of the mitochondria and this sensitivity is controlled through the 5'-flanking DNA sequence of this gene.

Cellulase↗
PubMed1997

Extracellular cellulase system of a thermotolerant streptomycete: Streptomyces albaduncus.

During screening for cellulolytic streptomycetes from different natural substrates, Streptomyces albaduncus thermotolerant streptomycete was selected for detailed studies because of its comparatively better yield and ability to grow at higher temperatures (up to 47 degrees C). The production of cellulases of this strain was studied under different growth conditions. It produced optimum levels of all the three constituents of cellulase complex at pH 7.0, and 37 degrees C in the presence of 3% substrate. When grown as submerged culture complex under these conditions, the strain produced considerable amounts of filter paper degrading activity (FPase), carboxymethyl cellulose hydrolyzing activity (CMCase) and beta-glucosidase activity in the extracellular supernatant. It exhibited good overall cellulolytic activity as measured using cotton as substrate. The maximum yields of FPase and CMCase were obtained within 96-120 h and beta-glucosidase after 48 h. The optimum incubation temperature for enzyme activities was 50 degrees C and optimum pH in the range of 6.0-6.5. After analyzing the cellulase complex of S. albaduncus, we are now capable to improve it genetically for superior yields.

Cellulase↗
PubMed2004

Cloning of genes expressed early during cellulase induction in Hypocrea jecorina by a rapid subtraction hybridization approach.

The cellulase system of the filamentous fungus Hypocrea jecorina (Trichoderma reesei) is encoded by several cellobiohydrolase, endoglucanase and beta-glucosidase genes, which are co-ordinately expressed upon induction by cellulose or the disaccharide sophorose. To identify genes, which are specifically expressed under these inducing conditions and possibly related to the induction process, we applied rapid subtraction hybridization (RaSH) to sophorose induced mRNAs from the wild-type strain H. jecorina QM9414 and a mutant strain H. jecorina QM9978, which is defective in the induction of cellulase gene expression. From a total of 224 clones, 22 gene fragments representing 20 different genes were analyzed. These included one gene encoding a PAS-domain protein with similarity to the Neurospora clock modulator VIVID; one gene similar to Podospora anserina ami1 involved in nuclear migration and the genes encoding translation elongation factor 1alpha, the transcriptional activator Hap5, and myo-inositol-1-phosphate synthase; in addition, several genes were detected, whose function is unknown. Some of them did not even have potential homologues in the Neurospora or Fusarium genome databases. The differential regulation of expression of those 20 genes by sophorose in wild-type and mutant was verified by Northern blotting. Their consistent response to additional inducing conditions (cellulose) confirms their interconnection with cellulase formation.

Blotting, Northern↗
PubMed2000

Surface hydrophobic amino acid residues in cellulase molecules as a structural factor responsible for their high denim-washing performance.

The denim-washing performance of six purified fungal cellulases (four endo-1,4-beta-D-glucanases and two cellobiohydrolases) was compared using a model microassay. The performance of cellobiohydrolases per mg of protein was much lower than that of endoglucanases. For endoglucanases, it varied up to 5 times between the best and the worst enzyme. Experiments with amino acids immobilized on cross-linked agarose showed that their side chains may bind indigo owing to hydrophobic interactions and formation of hydrogen bonds. The best binding effects provided Tyr and Phe. Analysis of three-dimensional structures of cellulase molecules showed that a certain correlation exists between the washing performance of enzyme and (i) quantity (percentage) of aromatic residues exposed to solvent on the surface of protein globule or (ii) overall percentage of the surface hydrophobic residues. Data presented provide an evidence that the molecules of certain cellulases, which have hydrophobic domains (clusters of closely located non-polar residues) on their surface, may bind indigo and thus act as emulsifiers helping the dye to float out of cellulose fibers to the bulk solution.

Journal Article↗
PubMed1969

The cellulase of Fusarium solani. Resolution of the enzyme complex.

1. Culture filtrates from Fusarium solani were fractionated by ion-exchange chromatography on DEAE-Sephadex, followed by gel chromatography on Sephadex G-100, into a C(1) component, a C(x) component (CM-cellulase) and a beta-glucosidase (cellobiase) component. 2. The individual components showed little capacity for the solubilization of cotton fibre (cellulase activity), but when recombined in their original proportions 81% of the original cellulase activity was recovered. 3. The C(1) components of F. solani and Trichoderma koningii were similar in their pH optima, heat stabilities over the pH range 5-8 and elution volumes on Sephadex G-100. 4. The C(1) component of F. solani synergized with the C(x) component of T. koningii and conversely. 5. The C(1) and the beta-glucosidase components of F. solani were devoid of the swelling-factor (S-factor) activity associated with the C(x) component.

Cell-Free System↗
PubMed1970

The formation of short fibres from native cellulose by components of Trichoderma koningii cellulase.

Cellulolytic enzyme components of culture filtrates of Trichoderma koningii were fractionated on ionic and non-ionic forms of Sephadex and on cellulose powder (Whatman) and examined for their ability to hydrolyse soluble carboxymethyl-cellulose, and to saccharify, solubilize and form short fibres from native undegraded cellulose of the type found in cotton. DEAE-Sephadex provided two CM-cellulase components and a C(1) component; the C(1) component acted weakly and solely on cotton, forming soluble products but not short fibres. The ability to form short fibres was confined almost wholly to one of the CM-cellulase components which completely degraded cotton, minimally to soluble products and extensively to short fibres. The latter action was unaffected by the presence of the other two components. The two CM-cellulase components solubilized cellulose synergistically whereas the short-fibre-forming component and C(1) component were inhibitory.

Cellulose↗
PubMed1971

The cellulase of Fusarium solani. Purification and specificity of the -(1-4)-glucanase and the -D-glucosidase components.

1. Cell-free culture filtrates of the fungus Fusarium solani were examined for homogeneity with respect to beta-d-glucosidase and C(x) activities. 2. o-Nitrophenyl beta-d-glucoside and cellobiose were both used as substrates for beta-d-glucosidase activity. 3. No evidence for the non-identity of nitrophenyl beta-d-glucosidase and cellobiase activities could be found, either by heat treatment, gel filtration on Sephadex G-100 or by isoelectric focusing. 4. The beta-d-glucosidase component was also a feeble exo-beta-glucanase: it had a molecular weight of approx. 400000. 5. The fall in viscosity of a solution of CM-cellulose, the formation of reducing sugars in a solution of CM-cellulose and the solubilization of phosphoric acid-swollen cellulose (Walseth cellulose), were all used for the measurement of C(x) activity. 6. The ratio of the two types of CM-cellulase activity was not changed after gel filtration on Sephadex G-100 or after chromatography on DEAE-Sephadex. 7. Three peaks of C(x) activity were obtained after electrofocusing, but all three possessed the same ratio of the two types of CM-cellulase activity as well as the same CM-cellulase/Walseth activity ratio, as the unfractionated enzyme; all three isoenzymes (isoelectric points, 4.75, 4.80-4.85 and 5.15) acted in synergism with a mixture of the C(1) and the beta-d-glucosidase components to the same extent in the solubilization of cotton fibre. 8. The molecular weight of the C(x) component was approx. 37000.

Cellulose↗
PubMed1972

The purification and properties of the C 1 component of Trichoderma koningii cellulase.

1. The C(1) component that was isolated from a Trichoderma koningii cellulase preparation (Wood, 1968) by chromatography on DEAE-Sephadex with a salt gradient was still associated with a trace of CM-cellulase activity (determined by reducing-sugar and viscometric methods). 2. Further chromatography on DEAE-Sephadex, with a pH gradient instead of a salt gradient, provided a C(1) component that could still produce reducing sugars from a solution of CM-cellulose (to a very limited extent), but which could no longer decrease the viscosity (i.e. under the assay conditions employed). 3. No evidence for the non-identity of C(1) component and the trace of CM-cellulase activity could be found when electrofocusing was done in a stabilized pH gradient covering three pH units (pH3-6) or, alternatively, only 0.5 pH unit (pH3.72-4.25). 4. The two protein peaks that were separated by electrofocusing in carrier ampholytes covering only 0.5 pH unit (isoelectric pH values of 3.80 and 3.95) were shown to be isoenzymes of the C(1) component: they differed in the extent to which they were associated with carbohydrate (9% and 33%). 5. The purified C(1) component had little ability to attack CM-cellulose or highly ordered forms of cellulose, but degraded phosphoric acid-swollen cellulose readily: cellobiose was the principal product of the hydrolysis (97%). 6. Dewaxed cotton fibre was degraded to the extent of 15% when exposed to high concentrations of C(1) component over a prolonged period: cellobiose was again the principal sugar present in the supernatant (96%). 7. Cellotetraose and cellohexaose were hydrolysed almost exclusively to cellobiose. 8. Evidence indicates that the C(1) component is a beta-1,4-glucan cellobiosylhydrolase.

Cellulose↗