Stability and immobilization of D-hydantoinase from Bacillus theorgensis on chitosan

D-hydantoinase (EC 3.5.2.2) was purified from Bacillus theorgensis with specific activity of 201.7 Umg-1 and 16.5-fold. The enzyme was successfully immobilized on chitosan bead. The best substrate for the enzyme was D-hydantoin followed by 5-hydroxy hydantoin, 5-phenyle hydantoin and 5-benzyle hydantoin. The optimal pH values were 8.0 and 9.0 for the free and immobilized enzyme, respectively. The optimal temperatures were 40 and 50 ºC for. Vmax values were 66.67 and 47.17 units mg-1 protein and Km values were 1.25 and 0.55 mM. The immobilized enzyme exhibited higher heat stability at 70 ºC, higher storage stability at 4 and 25 ºC than the free enzyme. The immobilized enzyme kept 80% of its activity after 7 cycles. Thus, D-hydantoinase represents a candidate to be used in the industry purpose