Enzyme-catalyzed synthesis of microalgae-derived biodiesel using a chemically modified immobilized lipase

Optimized synthesis conditions for biodiesel from microalgae oil and methanol using a modified immobilized lipase from Candida sp. as catalyst were investigated. The methanol tolerance of the immobilized lipase modified with succinic anhydride was determined. The results showed that the modified enzyme exhibited higher stability in methanol as compared with the unmodified enzyme. Then, the modified immobilized enzyme was applied to synthesize biodiesel using methanol and microalgae oil from Chlorella sp. Cells as substrates and the synthesis conditions were optimized. Tert-butanol was the most suitable organic solvent for biodiesel synthesis. The molar ratio of the reactants was found to be an important parameter affecting the yield of biodiesel. When the molar ratio of the methanol to microalgae oil was 5:1, the yield of biodiesel catalyzed by modified lipase reached the maximum of 92.5%. While the native immobilized Candida sp. lipase was used as catalyst, the yield of biodiesel got the maximum of 82.4% at the methanol / microalgae oil molar ratio of 4:1. The reuse stabilities of the modified enzyme and unmodified enzyme were also studied in the present work. These experimental results proved that the immobilized lipase modified with succinic anhydride was suitable for the synthesis of microalgae-derived biodiesel.