Bacterial cellulose nano crystal as hydrocolloid matrix in immobilized β-galactosidase onto silicon dioxide nanoparticles

Abstract

β-galactosidase immobilization was optimized on silicon dioxide nanoparticles for the hydrolysis of lactose using Design of Box-Behnken. Under optimized conditions, β-galactosidase immobilization exhibited efficiency 87% and enzyme activity 3.4 (U). Results of entrapment showed that maximum activity was obtained in ratio: bacterial cellulose nano crystal to immobilized enzyme (1:2). Optimum pH of free enzyme was 6 that after immobilization and entrapment shifted to 6.5. The optimal temperature for the free enzyme was 40 °C but for immobilization and entrapment reached to 50 °C. Entrapment and immobilization increased Km and decreased Vmax in comparison with free enzyme. The result indicated higher stability for entrapped in comparison with immobilized and free form after 45 days of storage at 4 °C. Entrapped enzyme retained about 80% of its initial activity after 12 cycles of use. Also, the results of FTIR, XRD, SEM, TEM and AFM confirmed the immobilization and entrapment. As a result, entrapment as a novel and productive method can improve enzyme efficacy in order to decrease the environmental pollution and the costs of food processing.