Two-step lipase catalysis for production of biodiesel

Lipase-catalyzed methanolysis of vegetable oils has attracted considerable interests for the production of biodiesel (BD). However, the activity of lipase such as Novozym 435 (immobilized Candida antarctica lipase B) is negatively affected by methanol. To minimize this problem, two-step lipase catalysis was investigated. Crude palm oil (CPO), which is relatively cheaper because of avoiding refining cost, was used as the source of BD. CPO was first hydrolysed to fatty acids (FA), which was then esterified to BD. Candida rugosa and Novozym 435 lipases were used as biocatalysts for the hydrolysis of CPO and the esterification of FA, respectively. The complete conversion of CPO to FA was achieved under an optimal condition of buffer to CPO ratio 1:1 (v/v), buffer pH 7.0, lipase 0.1 wt.% of CPO, isooctane to CPO ratio 1:1 (v/v), temperature 30 degrees C, shaking speed 250 rpm and time 4 h. The methyl esterification of FA with 1.2-fold stoichiometric excess of methanol reached the equilibrium after 2 h at which BD yield was 98%. C. rugosa and Novozym 435 lipases were repeatedly used for 10 and 50 cycles, respectively without significant loss of their activities. The developed two-step process is very promising because of its feedstock flexibility: it can be used for production of BD and FA from crude, refined and waste oils. (C) 2010 Elsevier B.V. All rights reserved.