Preparation and evaluation of some carriers for the immobilization of β-Galactosidase

N.Y.F. Almehbad
Faculty of Education for Female Teachers Najran, SA

Keywords: biocatalyst-immobilization-thermal stability properties

Summary:

Deferent carriers including tannin-Sepharose, tannin-chitosan, cyanogen bromide-activated Sepharose (CNBr- Sepharose), and polyacrylamide – co- N, N. methyl-bisacrylamide (PAMB) were prepared and evaluated for the immobilization of β –galactosidase from Aspergillus oryzae. The enzyme covalently immobilized on tannin-chitosan (epoxy activated) showed the highest immobilization yield. The bound enzyme retained 70% of the original specific activity exhibit by the free enzyme (7.5 U/ mg protein) compared to the free enzyme, the immobilized enzyme exhibited, lower optimum pH higher optimum reaction temperature, lower energy of activation higher Km (Michaels constant), and lower Vmax (maximal reaction rate). The half-life for the free enzyme was 52.6, 34.9 and min for 60, 70 and 80 0C respectively where as the immobilized from at the same temp had half-lives of 750, 136.6, and 40C 3.4 min. The deactivation rate constant at 80 0C for the immobilized enzyme is about 6.9X10-3min which is lower that of the free enzyme (10.6X10-3 min) the energy of thermal deactivated was thus 14.25 and 39.9 Kcal/mol, respectively for the free an immobilized enzyme, confirming stabilization by immobilization carrier (Tannin- chitosan) immobilized enzyme retained about 80% of the initial catalytic even after being used 10 cycles.