Microwave-assisted fatty acid methyl ester production from soybean oil by Novozym 435

Abstract

The production of fatty acid methyl ester (FAME) from soybean oil and methanol through transesterification by Novozym 435 (Candida antarctica lipase B immobilized on polyacrylic resin) was conducted under two different conditions—microwave irradiation and conventional heating—to compare their overall effects. It was found that, compared to conventional heating, microwave irradiation significantly increased the reaction rate by enhancing the activity of Novozym 435. The effect of the reaction conditions, such as water activity (aw), organic solvents, the ratio of solvent/oil, the ratio of methanol/oil, the pre-treatment method, methanol deactivation kinetics, enzyme dosage and temperature, on the activity of Novozym 435 were also investigated. Under the optimum conditions (aw of 0.53, tert-amyl alcohol/oil volume ratio of 1 : 1, methanol/oil molar ratio of 6 : 1, 3% Novozym 435 and 40 °C), a 94% yield of FAME could be achieved in 12 h under microwave irradiation, compared to 24 h under conventional heating. Furthermore, the repeated use of Novozym 435 for five cycles under microwave irradiation resulted no obvious loss of enzyme activity, suggesting that this enzyme is stable under microwave irradiation conditions. These results show that microwave irradiation is a fast and efficient method for FAME production.