Evaluation of the activities of concentrated crude mannan-degrading enzymes produced by Aspergillus niger

ABSTRACT

The mannan-degrading enzymes produced by Aspergillus niger were concentrated and the activities were evaluated. The optimum pH for -mannanase, endoglucanase and -galactosidase were obtained at pH 3.5 while pH optimum for -mannosidase was occurred at pH 3.0. The -mannanase, endoglucanase, -mannosidase and -galactosidase was stable at pH 3.5 to 7, pH 3.5 to 6.5, pH 4 to 7 and pH 3.5 to 5.0, respectively. The enzymes obtained in this study were characterized and defined as acidic proteins. The -mannanases from A. niger had two optimum temperatures (at 50 °C and 60 °C) and its half-life was 6 h and 4 h at 60 °C and 70 °C, respectively. The -mannosidase, endoglucanase and -galactosidase displayed optimal activity at 70 °C, 60 °C and 50 – 60 °C, respectively. The -mannosidase had half-life of 1.5 h at 70 °C, while -galactosidase had a half-life of 2.5 h at 60 °C and endoglucanase had a half-life of 6 h at 60 °C and 45 min at 70 °C.