Efficient biodiesel production from waste cooking oil by fast co-immobilization of lipases from Aspergillus oryzae and Rhizomucor miehei in magnetic chitosan microcapsules

Abstract

To achieve an efficient and cost-effective conversion from waste cooking oil (WCO) to biodiesel, a facile one-pot co-immobilization of Aspergillus oryzae lipase (AOL) and Rhizomucor miehei lipase (RML) was developed by rapid encapsulation of magnetic chitosan microcapsules. The encapsulation process was accomplished by self-assembly of negatively charged magnetic nanoparticles (citrate modified Fe3O4) on ionic cross-linked chitosan-citrate aggregates containing lipases. Integrating Tween 80 bio-imprinting of lipases, the co-immobilized AOL@RML (co-im Tween 80-AOL@RML) achieved a significant increase in activity and reached 98.5 % biodiesel yield under optimal conditions, which was 1.3 and 1.6 times higher than that of single immobilized AOL and RML, respectively. Notably, owing to the beneficial synergistic impact of methanol-tolerable AOL and thermal-stable RML, co-im Tween 80-AOL@RML displayed superior activity over single lipase counterparts under excess methanol and variable temperatures. The co-im Tween 80-AOL@RML could maintained 96 % activity after 3 cycles of biodiesel production; however, showed an obvious inactivation after continued reuse. Moreover, methanol-induced denaturation of lipases and glycerol-caused agglomeration of the magnetic nanoparticles during continued transesterification were ascertained by fourier transform infrared analysis and scanning electron microscopy. This study provides new pathways for constructing multi-lipase co-immobilzation as well as an economical and effective biocatalyst for biodiesel production from WCO.