Lipase oriented-immobilized on dendrimer-coated magnetic multi-walled carbon nanotubes toward catalyzing biodiesel production from waste vegetable oil

A polyamidoamine (PAMAM) dendrimer was grafted onto magnetic multi-walled carbon nanotubes (mMWCNTs) to combine magnetic properties with a large surface functionalized with amino groups. Based on three dimensional structural (3D) analysis of enzyme, oriented-immobilization of Rhizomucor miehei lipase (RML) on the obtained m-MWCNTs-PAMAM matrix was achieved. The recovery activity of the immobilized lipase was up to 2808% and the corresponding esterification activity was 27-fold higher than that of the free enzyme. The immobilized enzyme was employed to catalyze biodiesel production from waste vegetable oil in a tert-butanol solvent system. Biodiesel conversion reached 94% under optimal conditions. Moreover, the immobilized lipase could be easily recovered and there was no significant decrease in conversion rates after 10 cycles of reuse. The results suggested that the immobilized RML is a potential catalyst with high stability and excellent operational reusability for biodiesel production. (C) 2016 Elsevier Ltd. All rights reserved.