β-Galactosidase mediated synthesized nanosupport for the immobilization of same enzyme: Its stability and application in the hydrolysis of lactose

Abstract

β-Galactosidase was immobilized on modified nanosilver reduced graphene oxide (Ag@rGO) nanocomposite prepared by in vitro synthesis using same enzyme. The effectiveness factor, η value of the immobilized enzyme was calculated to be 0.968, suggesting enhancement in enzyme activity after immobilization. The morphological structure of the crosslinked biopolymer was analyzed using electron microscopy and other characterization techniques. The kinetics displayed a decrease in Km value from 0.50 to 0.44 mmol L−1 while there was an increase in Vmax values from 0.031 to 0.039 μmol min−1 mL−1. The immobilized enzyme retained 85% activity after its 10th repeated use. Inhibition constant (Ki) value suggests galactose to be a more potent inhibitor of the enzyme. Despite the inhibitory potential of these hydrolysis products, the immobilized enzyme preparation retained 44.2% activity in the presence of both inhibitory sugars. The as-synthesized nanobiocatalyst was found quite effective in hydrolyzing 89% of lactose from whey. Hence, this nanobiocatalyst can be used in removing lactose from dairy waste, whey before releasing it into the water bodies. Also, the cytotoxicity and genotoxicity of Ag@rGO NC was assessed on human blood lymphocytes using flow cytometry and comet assay, respectively.