Studies On Liquid Fermentation Of Cellulases And Purification Of An Endocellulase From Chaetomium Thermophile

Cellulose is by far the most abundant carbohydrate available from plant biomass, and can be converted into glucose by cellulase. The cellulase system in fungi is considered to comprise three hydrolytic enzymes: cellobiohydrolase, endocellulase, glucosidase. The hydrolyzation of cellulose is the cooperative action of the three types of enzyme.Cellulases from the thermophiJic fungi have reported to be stable at high temperature and like mesophilic fungi, the thermophilic fungi produce multiple froms of the cellulase components.C. thermophile, one of the thermophilic fungi, is a metatrophic soil fungus, and canbe thrive at temperature between 45 and 50, while most fungi will die above 40. Reporters about cellulase from C. thermophile have been few in the word, especially in China. C. thermophile used in the present study was isolated in China.In the first part of the article, we did some basal studies on the Studies on liquid-state fermentation for and properties of cellulase from C. thermophile. By the liquid-state fermentation, the best factors for cellulase from C. thermophile were investigated. The factors including carbon sources, nitrogen sources, the original pH of medium and varieties of pH and the protein concentration during the cultural process were tested .The result showed that when the medium contained 2% celluse , 2.0% KNO3, 0.2%Yeast and 1% dissolvable starch, the original pH was 6.5,and the optimum time was 9 days under the temperature of 50, activities of cellulase were high. During the first three days, either pH or protein decreased, but after then the both raised. The optimum temperature and pH of FPA were 60 and 5.5-6.0, respectively. FPA could endure high temperature (50 -65) and low pH (4.5-6.0).In the second part of the article, an endocellulase from culture supernatant of a thermophlic fungus C. thermophile was purifided to homogeneity, by using ammonium sulfate fraction, DEAE-Sepharose chromatography, Phenyl-Sepharose chromatography and Sephacryl S-100 chromatography. The enzyme was a glycoprotein with an apparent molecular weight of 67.8kDa and 69.8kDa, as determinded by 12.5% SDS-PAGE and gelfiltration, respectively. The crystalline body of the enzyme had been attained in the Turku biological technology center, Finland. The endocellulase was optimally active at pH 4.0-4.5 and 60. It was thermostable at 60 and retained 30% activity after 60min at 70 . The half life time of the enzyme at 80 was 25min. Different metal ions showed different effects on the endocellulase activity. Na+ enhanced the enzyme activity, whereas Fe2 Ag Cu2, Ba2 Zn2+cause obvious inhibition. The enzyme did not hydrolyze cellobiose, and was special for molecules containing p-l,4-glycosidic linkages.The products of the endocellulase hydrolying microcrystalline cellulose are oligosaccharies (C3 or C4 or C5) . It also didn't work on crystalline celllose and showed high activity towards CMC.