Immobilization of Aspergillus oryzae β-galactosidase in ion exchange resins by combined ionic-binding method and cross-linking

Abstract

The main objective of the present work is to study the immobilization process of Aspergillus oryzae β-galactosidase using the ionic exchange resin Duolite A568 as carrier. Initially, the immobilization process by ionic binding was studied through a central composite design (CCD), by analyzing the simultaneous influences of the enzyme concentration and pH on the immobilization medium. The results indicate that the retention of enzymatic activity during the immobilization process was strongly dependant of those variables, being maximized at pH 4.5 and enzyme concentration of 16 g/L. The immobilized enzyme obtained under the previous conditions was subjected to a cross-linking process with glutaraldehyde and the conditions that maximized the activity were a glutaraldehyde concentration of 3.83 g/L and cross-linking time of 1.87 h. The residual activity of the immobilized enzyme without glutaraldehyde cross-linking was 51% of the initial activity after 30 uses, while the enzyme with cross-linking immobilization was retained 90% of its initial activity. The simultaneous influence of pH and temperature on the immobilized β-galactosidase activity was also studied through a central composite design (CCD). The results indicate a greater stability on pH variations when using the cross-linking process.