Immobilization and Stabilization of Pectinase on Casein-Nanoclay Nanobiocomposite Beads for Apple Juice Clarification

Abstract

In this study, pectinase was stabilized on casein-montmorillonite activated by glutaraldehyde as a cross linker. To assess the efficiency, free and stabilized enzymes were used in the clarification process of fresh apple juice. The enzyme stabilization on the casein-MMT substrate increased pectinase activity by 98.67 ± 1.99% in pH = 5 and by 99.4 ± 0.7 at 60 °C, with the highest enzyme activity compared to the free enzyme. The stabilized pectinase showed higher thermal stability than the free enzyme so the latter preserved about 70.14% of its activity at 50 °C after 80 min while the stabilized enzyme maintained 80.54% of its activity at the same temperature. The values of kinetic parameters (Vmax, Km, and Kcat) decreased significantly in the stabilized enzyme than in the free one. Reusability using frequent cycles indicated that more than 63% of the stabilized pectin's initial activity was maintained after six cycles of reuse.

Keywords: Apple juice, stabilization, pectinase, clarification, montmorillonite nanoclay, casein protein