Hydrolysis of isoflavone glycoside by immobilization of β-glucosidase on a chitosan-carbon in two-phase system

Abstract

We explored a method to examine the hydrolysis of isoflavone glycoside by immobilizing β-glucosidase on chitosan-carbon beads in an aqueous–organic two-phase system. The chitosan-carbon beads were cross-linked with glutaraldehyde to immobilize β-glucosidase from Exiguobacterium sp. DAU5. The optimal pH and temperature were 9.0 and 55°C, respectively. Under the optimized conditions, crude and purified enzymes immobilized onto chitosan-carbon beads gave yields of 16.7% and 60%, respectively. The specific activities of immobilized crude and purified enzymes were 4.3U/g and 6U/g, respectively. The immobilized enzyme retained more than 80% of its maximum activity at pH 7.0–11.0, while temperature was more influential (80% activity after 40°C for 1.5h, but only 40% activity after 55°C for 0.5h, respectively. The immobilized enzyme was able to hydrolyze isoflavone glycoside in an aqueous–organic two-phase system, and the hydrolyzed products were enriched in the organic phase, making it easy to recover the products, i.e., genistein and daidein from the reaction system. These results suggest that immobilized β-glucosidase may be applicable for the industrial-scale hydrolysis of isoflavone glycoside.