Stability studies of β-galactosidase immobilized on gluconic acid coated fullerenes

The present study demonstrates the coating of fullerenes with gluconic acid for the immobilization of Aspergillus oryzae β-galactosidase. The prepared nanomatrix provided 86% immobilization yield, and broadened the biocatalytic activity of immobilized enzyme at higher pH and temperature ranges. Immobilized β-galactosidase exhibited 60% activity even at 5.0% galactose concentration as compared to 23% enzyme activity obtained by soluble enzyme under similar experimental conditions. Reusability of the enzyme was improved considerably as a result of covalent immobilization. Immobilized β-galactosidase showed 89% activity even after sixth repeated use and could be recovered easily. The noticeable improvement in lactose hydrolysis was observed in batch reactors by immobilized enzyme in contrast to the soluble enzyme at high temperature ranges. At 50 °C, 89% lactose conversion was achieved by immobilized enzyme as compared to 77%, obtained by free β-galactosidase under similar incubation conditions. Hence, the developed immobilized enzyme preparation could be exploited for converting lactose into its monosaccharides in a convenient and cheaper way.