Development of enzyme immobilization methods by covalent binding using chitosan supports and sol-gel technology

Abstract

We immobilized enzyme onto chitosan beads after treating them by glutaraldehyde to form aldehyde group as a cross-linker. We studied the optimum conditions for immobilizing ω-Transaminase onto the chitosan beads and under these conditions, the investigation to improve operational stability was also performed. During the immobilizing procedure, the pH value plays a crucial role on the efficiency of immobilization and the activity. The optimum value of pH for immobilization is 5.5, almost similar digit to the enzyme's pI value. The efficiency of immobilization decreased sharply beyond the optimum region. By adding the pyridoxal 5-phosphate (PLP), the cofactor of ω-Transaminase, into the substrate solution and by skirting the substrate inhibition, we could see a great improvement of the operational stability. The remained activity after 5 times reuse improved to 90% from 16% of initial value. We also could prepare sol-gel beads for enzyme encapsulation. Our experiments mainly focused on the procedure to produce the sol-gel bead more uniformly in shape. By controlling the solvents and sol conditions, we can get sphere shaped solgel beads with relatively small in size.