Enhanced stability of Kluyveromyces lactis β galactosidase immobilized on glutaraldehyde modified multiwalled carbon nanotubes

• We have studied the immobilization of Kluyveromyces lactis β galactosidase on glutaraldehyde modified multiwalled carbon nanotubes (MWCNTs).
• MWCNTs were characterized by UV-spectra, XRD analysis, TEM while the modified nanomatrix was observed for thermogravimetric analysis and differential thermal analysis.
• The results showed remarkable stability of immobilized enzyme against various physical and chemical denaturants.
• Immobilized β galactosidase exhibited greater percent of lactose hydrolysis at higher temperature as compared to enzyme in solution.
• The enhancement of activity and stability of immobilized enzyme is interesting for potential industrial use in obtaining lactose free dairy products.

The present study demonstrates covalent immobilization of Kluyveromyces lactis β galactosidase on functionalized multi-walled carbon nanotubes (MWCNTs). Highly efficient surface modification of MWCNTs was achieved by glutaraldehyde for binding greater amount of enzyme. X-ray diffraction analysis and UV visible spectroscopy of MWCNTs showed them to be entirely dispersive in aqueous solution. Transmission electron microscopy showed that MWCNTs were of 20 nm size. Thermogravimetric analysis further revealed the stability of glutaraldehyde modified MWCNT as an ideal matrix for enzyme immobilization. The optimal pH for soluble and immobilized β galactosidase was observed at pH 7.0 while the optimal operating temperatures were observed at 40 °C and 50 °C, respectively. Moreover, our findings demonstrated that β galactosidase immobilized on surface functionalized MWCNTs retained greater biocatalytic activity at higher galactose concentration, and upon repeated uses as compared to enzyme in solution.

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