Conversion of vegetable oil to biodiesel using immobilized Candida antarctica lipase

Biodiesel derived from vegetable oils has drawn considerable attention with increasing environmental consciousness. We attempted continuous methanolys is of vegetable oil by an enzymatic process. Immobilized Candida antarctica lipase was found to be the most effective for the methanolysis among lipas es tested. The enzyme was inactivated by shaking in a mixture containing mo re than 1.5 molar equivalents of methanol against the oil. To fully convert the oil to its corresponding methyl esters, at least 3 molar equivalents o f methanol are needed. Thus, the reaction was conducted by adding methanol stepwise to avoid lipase inactivation. The first step of the reaction was c onducted at 30 degrees C for 10 h in a mixture of oil/methanol (1:1, mol/mo l) and 4% immobilized lipase with shaking at 130 oscillations/min. After mo re than 95% methanol was consumed in ester formation, a second molar equiva lent of methanol was added and the reaction continued for 14 h. The third m olar equivalent of methanol was finally added and the reaction continued fo r 24 h (total reaction time, 48 h). This three-step process converted 98.4% of the oil to its corresponding methyl esters. To investigate the stabilit y of the lipase, the three-step methanolysis process was repeated by transf erring the immobilized lipase to a fresh substrate mixture. As a result mor e than 95% of the ester conversion was maintained even after 50 cycles of t he reaction (100 d).