Preparation and properties of α-amylase immobilized on silk fibroin.

Cavernous basified fibroin was prepared from degumed silk which pretreated with dilute alkali solution and served as supporter for immobilization of α amylase to form the basified fibroin immobilized α amylase, BFIA. The BFIA has a total activity of 439.81 U/g, a recovery rate of 48.33%, and an activity express ratio of 74.18%. Fibroin powder prepared by dissolving fibroin in CaCl 2 solution, desalting and subsegment treatment, was used as supporter for immobilization of α amylase, the so called fibroin powder immobilized α amylase, FPIA when the adsorbed α amylase was immobilized by the cross linking agent glutaraldehyde. The activity, the activity recovery ratio and the activity express ratio of FPIA were 509.09 U/g, 58.33% and 83.454% respectively. Our research showed that both basified fibroin and fibroin powder immobilize α amylase satisfactorily, their optimum temperature being 10 ℃ high and optimum pH 0.8 1.0 units lower as compared to the free α amylase. Experiment showed that the immobilized α amylase had longer work half life (26 38 d), high assistance to the action of resisting protein denaturing agent (over 80% of enzyme activity was retained in 8 mol/L urea solution) and improved stability for storage more than 50% of enzyme active remained after being stored for 60 days. It was found that the optimum enzyme concentration for preparation of immobilized α amylase was 2.8 3.2 g/L, and the optimum glutaraldehyde concentration was 0.25%.