Biodiesel is a mixture of fatty acid alkyl esters obtained by thetransesterification of triglycerides (TAGs) of vegetable or animalorigin with methanol or ethanol [39–41]. Because of the afore-mentioned tolerance of lipase SL-4 toward methanol and ethanol,transesterification between soybean oil and either of the two acylacceptors was performed using this lipase as a potential biocatalyst.As shown in Fig. 7 a, using methanol and ethanol, the conversionrates of soybean oil to FAMEs/fatty acid ethyl esters (FAEEs) were44.95% and 30.65%, respectively, illustrating that methanol is bet-ter than ethanol for lipase SL-4-mediated transesterification forbiodiesel production. Additionally, because the price of ethanol isconsiderably higher than that of methanol, researchers have takeninto account the cost of biodiesel yield, and chosen methanol as anacyl acceptor for enzymatic catalysis [10,38,41].