DIFFERENTIAL EFFECT OF ADDITIVES ON THERMOSTABILITY OF β-GLUCOSIDASE FROM ASPERGILLUS NIGER S1

Abstract

Growth of Aspergillus niger S1 on 2% wheat bran for 14 days produced 5973 IU/L of thermostable â-glucosidase under submerged culture conditions. The fungi also produced enoglucanase (1678IU/L) in the medium. The cellulases were stable at initial pH and temperature of 4 and 25°C respectively. The endoglucanase showed half-life of 15 min at 72oC and 30 min at 59oC. The â-glucosidase was thermostable with half-life for 90 min and 30 min at 70oC and 80oC but only for 15 min at 90°C. The addition of various additives increased the thermostability of these enzymes appreciably. Addition of 30% sorbitol and 50% glycerol increased the half-life of â-glucosidase to 120 and 100 min respectivly at 90oC. Sorbitol (20%), glycerol (30%) and PEG (1%) also offered protection against thermal inactivation