Lipase-catalyzed irreversible transesterification of vegetable oils for fatty acid methyl esters production with dimethyl carbonate as the acyl acceptor

Dimethyl carbonate (DMC) was used in the enzymatic transesterification of vegetable oils, which resulted in an irreversible reaction benefiting fatty acid methyl esters production. Among the tested lipases, Novozym435 (lipase B from Candida antarctica) led to a higher conversion for all tested vegetable oils in the initial screening. DMC used as the acyl acceptor, the conversions of cottonseed oil, soybean oil and rapeseed oil were two to three times higher than those of conventional acyl acceptors (methanol and methyl acetate). Using cottonseed oil as the feedstock, a very high conversion of 96.4% could attain under the optimized conditions. This optimal condition was further applied to other vegetable oils. All of them showed very high conversion except sesame oil. Although the Novozym435 activity was impaired severely by the bound glycerol, it could remain about 80% activity after five batch reactions if only it was washed with acetone after each batch.