Fractionation and lipase-catalyzed conversion of microalgal lipids to biodiesel

Abstract

This study was conducted to evaluate the lipid fractionation and purification procedures of lipase-catalyzed conversion of neutral lipids to microalgal biodiesel. Microalgae lipids were efficiently recovered and purified by a combined extraction method and crude lipid extracts were separated into neutral lipids, glycolipids, and phospholipids by solid-phase extraction. The high purity of the neutral lipids fraction was confirmed by its low concentration of phosphorous (< 2.0 ppm). Transesterification was catalyzed by immobilized Candida antarctica lipase for 72 h with stepwise addition of methanol. The reaction displayed Michaelis–Menten kinetics and produced high yields of microalgal biodiesel (91.2% in the case of Dunaliella salina) with a high content of unsaturated fatty acids (81.5%). Neutral lipids were converted to biodiesel by three-step transesterification, while the removal of polar lipids maintained the activity of the immobilized lipase by reducing both reaction mixture viscosity and contamination risk.