Synthesis and characterization of biodiesel from waste cooking oil by lipase immobilized on genipin cross-linked chitosan beads: A green approach

Alternative fuels are the need of time because of finite fossil fuels. Biodiesel produced by enzyme-catalyzed transesterification is an environment-friendly and greener alternative fuel. However, the main shortcoming of biodiesel production is high cost of production. Successful recovery for high cost of production is the use of waste cooking oils. In this study, lipase from porcine pancreas was immobilized on genipin cross-linked chitosan for catalyzing the transesterification of waste cooking oil to produce biodiesel in presence and absence of solvents. Solvents in a reaction mixture keep the essential water layer around lipase intact, which protects lipase from methanol inactivation. Our result showed no significant effect of solvent on transesterification reaction, suggesting the resistant nature of lipase against methanol. This bypasses the need to recover the solvent, making the process more economical. The structural morphology of genipin cross-linked chitosan beads was studied by SEM. The conversion of waste cooking oils into Fatty acid methyl ester (FAME) was analyzed by Gas Chromatography. Under the optimized conditions of 9:1 methanol/oil molar ratio, water content 6% (w/w) enzyme, at 40oC, 10-hr reaction time, 7.5 wt% catalyst loading at 150 rpm, the ester yield was found to be 92.33%, with good reusability in solvent-free system. The obtained biodiesel was characterized by H-1 NMR, C-13 NMR, and FTIR spectroscopy. The biodiesel synthesis in solvent-free system described in the study is a prospective economical method for the synthesis of the biodiesel with more than 90% yield and good reusability.