| Abstract: | The conversion of soybean oil to biodiesel fuel was investigated in the presence of a lipase from Thermomyces lanuginosus (commercially called Lipozyme TL IM) in a solvent-free medium. The lipase was inactivated when more than 1.5 molar equivalent of methanol was added to the oil mixture. To fully convert the oil to its corresponding methyl esters, the reaction was performed successfully by a three-step addition of 1 molar equivalent of methanol and under the optimized conditions (40°C, 150 rpm, 10% enzyme quantity based on oil weight), the maximum methyl ester (ME) yield was 98% after 12 h reaction. By-product glycerol had a negative effect on enzymatic activity and iso-propanol was found to be effective for glycerol removal, in the presence of which lipase expressed relatively high activity and more than 94% of the ME yield was maintained after being used repeatedly for 15 batches. |
