Lipase immobilized on polydopamine-coated magnetite nanoparticles for biodiesel production from soybean oil

Abstract

Lipase from Pseudomonas cepacia was covalently attached to magnetite nanoparticles coated with a thin polydopamine film, and employed in the enzymatic conversion of soybean oil into biodiesel, in the presence of methanol. The proposed strategy explored the direct immobilization of the enzyme via Michael addition and aldolic condensation reactions at the catechol rings, with no need for using specific coupling agents. In addition, a larger amount of enzymes could be bound to the magnetic nanoparticles, allowing their efficient recycling with the use of an external magnet. For biodiesel production, the transesterification reaction was carried out directly in soybean oil by stepwise addition of methanol, in order to circumvent its inactivation effect on the enzyme. A better yield of 90% was achieved at 37°C compared with the free enzyme. However, the immobilized biocatalyst became gradually less effective after the third cycle, due to its prolonged exposition to the denaturating methanol medium.