Nanodiamonds as an effective and novel matrix for immobilizing β galactosidase

• Nanodiamonds provided large surface area for immobilization of β-galactosidase.
• Immobilized enzyme showed greater biocatalytic activity in terms of selectivity, loading and stability.
• Immobilized β galactosidase exhibited greater hydrolysis of lactose from solution as compared to soluble enzyme.

The present study demonstrates the biospecific adsorption of Aspergillus oryzae β galactosidase on glutaraldehyde functionalized nanodiamonds (NDs). Transmission electron microscopy showed that the synthesized NDs were of 20 nm size. Enzyme activity retained as a result of immobilization was 7420 U/gm of modified NDs. The optimal pH and temperature for soluble and immobilized β galactosidase was observed at pH 4.5 and at 50 °C, respectively. However, significant stability was observed at both higher and lower limits of pH and temperature for the enzyme immobilized on glutaraldehyde modified NDs. Moreover, our findings demonstrated that β galactosidase immobilized on surface functionalized NDs retained greater biocatalytic activity even after 2 months of storage and at higher galactose concentration, and upon repeated uses as compared to enzyme in solution. Modified NDs bound β galactosidase showed improved hydrolysis of lactose from solution in batch processes at various temperatures even after 10 h, thereby suggesting its use for hydrolyzing lactose in dairy products.

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