Functionalized Multi-Wall Carbon Nanotubes for Lipase Immobilization

We examine the immobilization of lipase B from Candida antarctica on functionalized multi-wall carbon nanotubes (MWCNTs) through physical adsorption. MWCNTs functionalized with carboxyl-, amine- and ester- terminal groups on their surface are used as immobilization carriers. Dispersion of the nanotubes and the immobilization procedure take place in aqueous and low-water media. High enzyme loadings are attained, up to 25% of the weight of the carbon nanotubes. These novel biomaterials are characterized though FT-IR and Raman spectroscopy. The MWCNT-lipase bioconjugates exhibit high catalytic activity and increased storage and operational stability. The biomaterials retain more than 55% of their initial activity after 6 months at 4 degrees C, while they retain approximately 25% of their initial activity after 30 d of incubation in hexane at 60 degrees C. The catalytic behaviour of the immobilized enzyme depends on the terminal group of the carbon nanotubes, the concentration of the enzyme and the immobilization method employed.