KINETIC AND IMMOBILIZATION STUDIES ON FUNGAL GLYCOSIDASES FOR AROMA ENHANCEMENT IN WINE

The biochemical properties of a commercial glycosidase from Aspergillus niger (Cytolase PCL5, Genencor) were investigated. The product contains beta-glucosidase, alpha-arabinosidase, and alpha-rhamnosidase activities in a ratio considered ed suitable for aroma enhancement in wine-making. A kinetic study of these three activities was carried out, which included determination of kinetic constants; dependence of enzyme activity and stability on pH and temperature; and enzyme inhibition by glucose, fructose, glycerol, and sulfurous anhydride. These glycosidase activities were immobilized to a solid carrier with the aim of developing a continuous process for wine aroma enhancement. Immobilization was best achieved with silanized bentonite as the solid, activated carrier, with bound glutaraldehyde as the reactive arm at a protein:carrier ratio of 0.11. Immobilization reaction was carried out for 48 h at pH 4 and 30 degrees C. Under these conditions, 16 units of beta-glucosidase, 2 units of alpha-arabinosidase, and 4.5 units of alpha-rhamnosidase per gram of bentonite were immobilized.