Plasma Functionalized Multiwalled Carbon Nanotubes for Immobilization of Candida antarctica Lipase B: Production of Biodiesel from Methanolysis of Rapeseed Oil.

Surface modification of multiwalled carbon nanotubes (MWCNTs) through functionalization could improve the characteristics of these nanomaterials as support for enzymes. Carboxylation of MWCNTs (MWCNT-COOH) has been carried out in this study using the dielectric barrier discharge (DBD) plasma reactor through humidified air. The chemical method was also used for further functionalization of the MWCNT-COOH through which the amidation of the surfaces with either butylamine (MWCNT-BA) or octadecylamine (MWCNT-OA) was performed. By immobilization of Candida antarctica B lipase (CALB) on these nanoparticles, performance of the immobilized enzyme in catalyzing methanolysis of rapeseed oil was evaluated. The CALB loading on the MWCNT-BA and MWCNT-COOH was 20 mg protein/g, while the value for MWCNT-OA was 11 mg protein/g. The yield of biodiesel was determined as percentage of mass of fatty acid methyl ester (FAME) produced per initial mass of the oil, and the yield value for the two of these three supports namely, MWCNT-COOH and MWCNT-BA used for the CALB immobilization was similar at about 92 %, while 86 % was the yield for the reaction catalyzed by the lipase immobilized on MWCNT-OA. Thermal stability of the immobilized CALB and the catalytic ability of the enzyme in the repeated batch experiments have also been determined.