Biotechnological application of Aspergillus oryzae/3-galactosidase immobilized on glutaraldehyde modified zinc oxide nanoparticles

The current research demonstrates the synthesis of zinc oxide nanoparticles (ZnO-NPs) via green nanotechnology approach (Azatirachta indica leaves). The size of the synthesized ZnO-NPs was confirmed as 27 nm by TEM. Glutaraldehyde was used to modify the surface of the developed ZnO-NPs in order to promote covalent binding of Aspergillus oryzae beta-galactosidase. Enzyme ac-tivity was achieved as 93% on glutaraldehyde modified ZnO-NPs. The immobilized enzyme exhibited significant enhancement in activity under extreme temperature and pH variations, as compared to the soluble beta-galactosidase (S beta G). It was further observed that the immobilized enzyme retained 58% activity at 5% galactose concentration. However, under similar experi-mental conditions, S beta G showed 27% activity. Reusability of immobilized enzyme revealed that it retained 89% activity even after fifth repeated use, and hence could be recovered easily by centrifugation for repeated use in biotechnological applications. Batch reactor experiment in-dicates that the immobilized enzyme displayed 81% and 70% lactose hydrolysis at 50 degrees C and 60 degrees C, respectively as compared to 70% and 58% lactose hydrolysis by soluble enzyme under identical conditions after 9 h.