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At least 541 records · Page 30Linked to original sources
PubMed2006

Production of cellulase-free xylanase from Bacillus megaterium by solid state fermentation for biobleaching of pulp.

Xylanase production from B. megaterium was enhanced using solid state fermentation with respect to the use of solid substrate, moistening solution, moisture content, inoculum, sugars, soyabean meal, amino acids, and extraction with surfactant. An increase of approximately 423-fold in xylanase production and complete suppression of CMCase production was achieved over submerged liquid fermentation. Biobleaching using this cellulase-free xylanase, 8 U/g of oven dried pulp of 10% consistency, showed 8.12% and 1.16% increase in brightness and viscosity, 13.67% decrease in kappa number, and 31% decrease in chlorine consumption at the CD stage.

Bacillus megaterium↗
PubMed2003

A monovalent anion affected multi-functional cellulase EGX from the mollusca, Ampullaria crossean.

A cellulose hydrolytic enzyme was isolated from the stomach juice of Ampullaria crossean, a kind of herbivorous mollusca. The enzyme was purified 45.3-fold to homogenety by ammonium sulfate precipitation, DEAE-Sephadex A-50 column, Bio-gel P-100 gel filtration column, and phenyl-Sepharose CL-4B column chromatography. The enzyme was designated as cellulase EGX. The purified enzyme is a multi-functional enzyme with the activities of exo-beta-1,4-glucanase (14.84 U/mg for p-nitrophenyl beta-D-cellobioside), endo-beta-1,4-glucanase (40.3 U/mg for carboxymethyl cellulose), and endo-beta-1,4-xylanase (196 U/mg for soluble xylan from birchwood). The monovalent anions such as F(-), Cl(-), Br(-), I(-), and NO(3)(-) are essential for its exo-beta-1,4-glucanase activity but have no effect on the activity for xylan, while I(-) higher than 5mM would inhibit the exo-beta-1,4-glucanase activity. The monovalent anions Cl(-) and Br(-) activate its endo-beta-1,4-glucanase activity. Binding of Cl(-) enhances the thermostability of EGX, but does not affect its fluorescence emission spectrum. The molecular mass of EGX is 41.5 kDa, as determined by SDS-PAGE. The pI value is about pH 7.35. The xylan hydrolytic activity of EGX reaches to the maximum between pH 4.8 and 6.0 and the pNPC hydrolytic activity reaches the maximum between pH 4.8 and 5.6, while that for CMC hydrolytic activity is between pH 4.4 and 4.8. Preliminary results showed that the enzyme was secreted by the mollusca itself.

Ammonium Sulfate↗
PubMed2001

EndB, a multidomain family 44 cellulase from Ruminococcus flavefaciens 17, binds to cellulose via a novel cellulose-binding module and to another R. flavefaciens protein via a dockerin domain.

The mechanisms by which cellulolytic enzymes and enzyme complexes in Ruminococcus spp. bind to cellulose are not fully understood. The product of the newly isolated cellulase gene endB from Ruminococcus flavefaciens 17 was purified as a His-tagged product after expression in Escherichia coli and found to be able to bind directly to crystalline cellulose. The ability to bind cellulose is shown to be associated with a novel cellulose-binding module (CBM) located within a region of 200 amino acids that is unrelated to known protein sequences. EndB (808 amino acids) also contains a catalytic domain belonging to glycoside hydrolase family 44 and a C-terminal dockerin-like domain. Purified EndB is also shown to bind specifically via its dockerin domain to a polypeptide of ca. 130 kDa present among supernatant proteins from Avicel-grown R. flavefaciens that attach to cellulose. The protein to which EndB attaches is a strong candidate for the scaffolding component of a cellulosome-like multienzyme complex recently identified in this species (S.-Y. Ding et al., J. Bacteriol. 183:1945-1953, 2001). It is concluded that binding of EndB to cellulose may occur both through its own CBM and potentially also through its involvement in a cellulosome complex.

Amino Acid Sequence↗
PubMed1996

Crystallization of a family 8 cellulase from Clostridium thermocellum.

The catalytic domain of cellulase CelA, a family 8 glycohydrolase from C. thermocellum, has been crystallized in the orthorhombic space group P2(1)2(1)2(1) with unit cell dimensions a = 50.12 A, b = 63.52 A, c = 104.97 A. The diffraction pattern extends beyond 1.5 A resolution.

Cellulase↗
PubMed2000

Cellulases from the fungi Phanerochaete chrysosporium and Trichoderma reesei as chiral selectors in capillary electrophoresis: applications with displacer plugs and sample preconcentration.

The cellulases CBH 58 from the fungus Phanerochaete chrysosporium and CBH I from the fungus Trichoderma reesei were compared as chiral selectors in capillary electrophoresis (CE) applying the partial filling technique. Amines, e.g., norephedrine, two bambuterol analogs, as well as acids, e.g., di-p-toluoyl tartaric acid and dibenzoyl tartaric acid, which could not be enantioseparated in the liquid chromatographic use of the selectors, could be separated in the corresponding CE experiments. Due to the very high enantioselectivities, terbutaline, alprenolol and propranolol could be completely enantioresolved with selector plugs shorter than the sample plugs. The affinity of propranolol to CBH 58 was so high at pH 7.0 that neither of the enantiomers reached the detector; therefore, a plug of the displacing disaccharide cellobiose was injected after the sample to elute the propranolol enantiomers. The enantiomers could also be made to leave the capillary at opposite ends, thereby causing an infinite enantioresolution. A new preconcentration technique was introduced, which takes advantage of the very high affinity of propranolol to CBH 58 and the eluting ability of cellobiose. A 12.5 cm long plug of rac-propranolol could be preconcentrated and enantioseparated in a single procedure.

Cellulase↗
PubMed2000

Adsorption of thermomonospora fusca E(5) cellulase on silanized silica.

The adsorption kinetics and dodeceyltrimethylammonium-bromide-mediated elution of Thermomonospora fusca E(5) cellulase were recorded in situ, at hydrophobic, silanized silica. Experiments were performed at different solution concentrations, ranging from 0.001 to 0.70 mg/mL. Plateau values of adsorbed mass generally increased with increasing solution concentration, with the adsorbed layer being only partially eluted by buffer. Treatment with surfactant removed more of the adsorbed enzyme in each case, with the remaining adsorbed mass varying little among experiments. Adsorption of E(5) into this nonremovable state was suggested to occur early in the adsorption process and continue until some critical surface concentration was reached. Beyond this critical value of adsorbed mass, adsorption progressed with the protein adopting more loosely bound states. Adsorption kinetic data were interpreted with reference to an adsorption mechanism allowing for irreversible adsorption into two dissimilar states. These states were distinguished by differences in occupied interfacial area, and binding strength, presumably a result of differences in structure. Comparison of the data to the kinetic model based on this mechanism showed that the fraction of adsorbed molecules present in the more tightly bound state decreased as adsorption occurred from solutions of increasing concentration. However, the absolute values of more tightly bound molecules were less dependent on adsorption conditions.

Actinomycetales↗
PubMed2000

Adsorption of Trichoderma reesei CBHI cellulase on silanized silica.

Adsorption kinetics and surfactant-mediated elution of Trichoderma reesei CBHI cellulase were recorded in situ, at hydrophobic, silanized silica. Experiments were performed at different solution concentrations, ranging from 0.001 to 0.98 mg/mL. Adsorbed enzyme was partially elutable upon rinsing, with the amount of adsorbed mass remaining being highest at intermediate concentrations. In addition, the resistance to elution with buffer was generally lower at higher concentrations, and the resistance to elution with surfactant was generally lower at intermediate concentrations. These observations are tentatively explained with reference to a mechanism allowing for adsorption of associated monomers of CBHI as well as free monomers.

Adsorption↗
PubMed2001

Optimized mixtures of recombinant Humicola insolens cellulases for the biodegradation of crystalline cellulose.

The digestion of bacterial cellulose ribbons by ternary mixtures of enzymes consisting of recombinant cellulases (two cellobiohydrolases, Cel6A and Cel7A, and the endoglucanase Cel45A) from Humicola insolens was investigated over a wide range of mixture composition. The extent of digestion was followed by soluble sugar release (saccharification) analysis together with transmission electron microscopy (TEM) observations. It was found that the addition of minute quantities of Cel45A induced a spectacular increase in saccharification of the substrate with either Cel7A or the mixture of Cel6A and Cel7A. Conversely, only a moderate saccharification resulted from the mixing of Cel45A and Cel6A. This difference is believed to originate from (1) the occasional endo character of Cel6A and (2) the competition of Cel6A and Cel45A for the substrate sites that are sensitive to endo activity. Interestingly, the mixture of enzymes giving rise to the highest saccharification rate did not always correspond to mixtures of enzymes generating the highest synergy. TEM images revealed that the bacterial cellulose ribbons became at the same time cut and narrowed down under the action of an optimized mixture of the three enzymes.

Ascomycota↗
PubMed2003

Suggested improvements to the standard filter paper assay used to measure cellulase activity.

Two suggestions can be found in the literature to improve the reproducibility of the Mandels' filter paper assay: add supplemental cellobiase and increase the boiling time for color development. Here we provide data that strongly supports adding supplemental cellobiase. Adding supplemental cellobiase increased assay response by 56%. Cellulases from different sources have different cellobiase activities, which would cause significant variation in the assay response. There is no need for additional boiling time-5 minutes is sufficient. For maximum reproducibility, it is essential that the water bath vigorously boil so that temperature excursions are minimized.

Biosensing Techniques↗
PubMed2004

Rapid chromatography for evaluating adsorption characteristics of cellulase binding domain mimetics.

The cost of cellulolytic enzymes is one barrier to the economic production of fermentable sugars from lignocellulosic biomass for the production of fuels and chemicals. One functional characteristic of cellulolytic enzymes that improves reaction kinetics over mineral acids is a cellulose binding domain that concentrates the catalytic domain to the substrate surface. We have identified maleic acid as an attractive catalytic domain with pK(a) and dicarboxylic acid structure properties that hydrolyze cellulose while producing minimal degradation of the glucose formed. In this study we report results of a rapid chromatographic method to assess the binding characteristics of potential cellulose binding domains for the construction of a synthetic cellulase over a wide range of temperatures (20 degrees to 120 degrees C). Aromatic, planar chemical structures appear to be key indicators of cellulose adsorption. Indole, the side-chain of the amino acid tryptophan, has been shown to reversibly adsorb to cellulose at temperatures between 30 degrees and 120 degrees C. Trypan blue, a polyaromatic, planar molecule, was shown to be irreversibly adsorbed to cotton cellulose at temperatures of <120 degrees C on the time scale of the experiments. These results confirm the importance of hydrophobic cellulose and the cellulose-binding component of cellulolytic enzymes and cellulolytic enzyme mimetics.

Biomimetics↗
PubMed2004

Enhancement of tyrosinase inhibition of the extract of Veratrum patulum using cellulase.

Inhibitors of melanin biosynthesis were screened by using three different methods. The extract of Veratrum patulum contains hydroxystilbene compounds that are potent tyrosinase inhibitors. We evaluated the enzyme inhibitory property on the mushroom tyrosinase of hydroxystilbene compounds including resveratrol, oxyresveratrol, and their analogs. Biotransformation using cellulase of the whole extract brought about an increase in the inhibitory activity of the products on mushroom tyrosinase. The enhancement of tyrosinase inhibition is supposed to increase the concentration of aglycon, which has superior inhibitory activity to its glycoside. Eventually, melanin biosynthesis was inhibited by the enhanced tyrosinase inhibitory activity of the extract. This result indicated that deglycosylation of stilbene compounds has exerted more effective inhibition on the enzyme than that of the unprocessed plant extract.

Agaricales↗
PubMed1975

Cellulase and protein production from mixed cultures of Trichoderma viride and a yeast.

Fermentations with mixed cultures of the cellulolytic fungus Trichoderma viride and the yeast Saccharomyces cerevisiae or Candida utilis were examined. The fermentations were carried out in an aerated 5 liter fermentor with NaOH treated barley straw as the cellulose source (2-4%). Yeast was inoculated 24-32 hr after the fungus and the growth of the two organisms was followed through the production of CO2 and cell protein. In comparison with fermentations with T. viride alone, the production time for maximum yields of cellulases and cell protein was reduced by several days, depending on the straw concentrations. The protein content of the growth product was 21-22% and the amino acid composition of the product resembled that of T. viride alone.

Candida↗
PubMed1975

Kinetic studies on insoluble cellulose-cellulase system.

Enzymatic hydrolysis of insoluble amorphous cellulose by Trichoderma viride cellulase was investigated in a batch reactor at several substrate concentrations and three enzyme levels. The reactions were carried out at 50 degrees C and pH 4.8. Enzyme was rapidly adsorbed onto solids on contact, then gradually returned to the liquid phase as the reaction proceeded. A kinetic model that considered the fast adsorption which was followed by the slow reaction, and subsequent product inhibition was developed to interpret the experimental observations. The resulting equation successfully correlated the data for up to 70% conversion. The methods for determining the kinetic parameters are discussed.

Carbohydrate Metabolism↗
PubMed1979

Production of cellulases by Trichoderma reesei QM 9414 in fed-batch and continuous-flow culture with cell recycle.

The scope in improving enzyme productivities from the cellulose fermentation process is examined in laboratory-scale fermentors. The maximum productivity (30 IU/liter hr) is attained in a continuous-culture process with cell recycle using modified medium containing 0.5% cellulose. Optimum dilution rate and recycle ratio are determined as 0.025 hr-1 and 1.2, respectively, for the process. The system is analyzed and steady-state equations for predicting enzyme protein concentrations in the fermentor are developed. In fed-batch cultures, slow addition of cellulose at high concentrations can improve enzyme productivity by as much as 33% over a batch process. The scope and results of using modified medium for cellulase production are also presented.

Cellulase↗
PubMed1988

Purification of cellulases from Streptomyces strain A20 by electroendosmotic preparative electrophoresis.

Five cellulase components were identified and purified in one step from Streptomyces strain A20 using electroendosmotic preparative electrophoresis. By this procedure up to 18 mg of protein mixture could be loaded on the column, with an estimated recovery of 60-70% of total activity; activity and protein recovery could be estimated 32% and 47% respectively, if only activity peaks were considered. In comparison to other purification methods, this technique results in high protein recovery and resolution of applied samples.

Bacterial Proteins↗
PubMed1994

Catabolite repression of cellulase biosynthesis in Streptomyces albaduncus.

The cellulase complex of S. albaduncus was found to undergo catabolite repression in the presence of glycerol accompanied by a decrease in the pH of the medium. The results of the experiments conducted at two different initial pH of the medium suggested that pH effect as well as proteases were involved in the inactivation of glucanases (exoglucanase and endoglucanase) whereas beta-glucosidase inactivation was solely due to 'pH effect'. It was also apparent that pH change followed by the addition of glycerol caused alterations in protease activities as well as pattern of their production.

Cellulase↗
PubMed1996

Effect of cassavar cultivar, age and pretreatment processes of cellulase and xylanase production from cassava waste by Trichoderma harzianum.

Cassava wastes--the peel and the root fibre were taken through various pretreatment procedures before being subjected to solid state fermentation with Trichoderma harzianum. Most of the pretreatment processes increased the cellulose and hemicellulose content of the cassava peel and fibre by as high as 155% while sulfuric acid treatment resulted in 25.3% loss in the peel hemicellulose. The best pretreatment found to be 1% NaOH at 120 degrees C gave the highest production of the Cx, the Cl and xylanase enzymes with the cassava root fibre. Xylanase and cellulase production with the exception of the Cx was found to be affected by age while an improved cassava variety TMS(2) 1425 peel and fibre rated highest in terms of production of the enzymes. Percentage hydrolysis within range of 56.52-67.64% were recorded for the enzymes on sorghum grains.

Age Factors↗
PubMed2001

Enzymatic synthesis of aliphatic beta-lactosides as mimic units of glycosphingolipids by use of Trichoderma reesei cellulase.

Aliphatic beta-lactosides were directly synthesized by beta-lactosyl transfer reaction from p-nitrophenyl beta-lactoside (Lac beta-pNP) to various 1-alkanols (n = 2-12), utilizing commercially available cellulase preparation of Trichoderma reesei C1. With ethanol acceptor, the enzyme induced ethyl beta-lactoside (1) in 18% yield based on the donor added in aqueous buffer system. When 1-octanol and dodecanol were acceptors, octyl beta-lactoside (2) and dodecyl beta-lactoside (3) were also obtained as transfer products, respectively. In both cases, the addition of sodium cholate as detergent to the reaction system ensured a sufficient solubility of these acceptors and resulted in a remarkable increase of the desired compounds (5-13% yields based on the donor added). Furthermore, the enzyme catalyzed the N-acetyllactosaminyl transfer reaction from p-nitrophenyl beta-N-acetyllactosaminide (LacNAc beta-pNP) not only to 1-alkanol, but also to the OH-4 position of Man and Glc to produce the trisaccharides, Gal beta1-4GlcNAc beta1-4Man (4) and Gal beta1-4GlcNAc beta1-4Glc (5), respectively. The enzyme activities transferring lactosyl and N-acetyllactosaminyl groups were not separated by chromatographies using DEAE-Sepharose Fast Flow and Sephadex 75 pg columns, indicating that the two reactions were catalyzed by a single enzyme. It was specified that a single enzyme works both transglycosylations, based on the substrate competition assay on hydrolysis.

Amino Sugars↗