Surface functionalization of oxidized multi-walled carbon nanotubes: Candida rugosa lipase immobilization

Abstract

This work examines two approaches for immobilization of lipase from Candida rugosa on oxidized multi-walled carbon nanotubes (o-MWCNTs). One method included the presence of activating agents to promote covalent bonding and the other the adsorption on o-MWCNTs to elucidate if non-specific bonding on the o-MWCNTs surface exists. The influence of the immobilization time and initial enzyme concentration on protein loading and the expressed lypolitic activity of the immobilized preparation were investigated. The results showed that the enzyme adsorbs on o-MWCNTs in a maximal amount of 37 mu g mg(-1) CNTs, while the attached amount was more than 2-times higher under covalent promoting conditions (80 mu g mg(-1) CNTs). Furthermore, similar trends were observed for the lypolitic activity, whereby preparations obtained under covalent promoting conditions had almost 3-times higher activity (560 IU g(-1) of immobilized enzyme). In addition, immobilization of the enzyme was confirmed by Fourier transformation infrared spectroscopy and thermogravimetric analysis.