The mechanism of enzymatic cellulose degradation (I). Purification and some properties of cellulolytic enzymes from Aspergillus niger UC.

Abstract

Cellulases from a mutant (cellulase higher producer) obtained by UV treatment, Aspergillus niger UC were fractionated into Avicel hydrolyzing cellulase (Avicelase), carboxymethyl-cellulase (CMCase) and β-glucosidase by DEAE-Sepharose CL-6B column chromatography. Avicelase and CMCase were further purified by a multistep procedure involving Amberlite CG-50 and Sephadex G-100. Purification of β-glucosidase was carried out in three steps: by Sephadex G-100 followed by Amberlite CG-50 and Concanavalin A-Sepharose. All purified enzymes were homogeneous as judged by SDS polyacrylamide slab gel electrophoresis. The activities of both Avicelase and CMCase were optimum at pH 4.5 and 40-50°C. Avicelase was stable in the pH range 5.0 to 6.5 at temperatures below 50°C, while CMCase was stable in the pH range 4.0 to 7.0 at temperatures below 60°C. The molecular weights of Avicelase, CMCaseand β-glucosidase were estimated to be 80, 000, 32, 000 and 120, 000, respectively. A strong synergistic action was shown by the combination of Avicelase along with CMCase and β-glucosidase.