Mechanism exploration during lipase-mediated methanolysis of renewable oils for biodiesel production in a tert-butanol system.

tert-Butanol has been developed as a novel reaction medium for lipase-mediated methanolysis of renewable oils for biodiesel production, in which lipase could maintain high catalytic activity, although the log P value of tert-butanol was just about 0.35. The related mechanism exploration has been carried out, and it has been proposed first in this manuscript that in the biodiesel production system, log P(environment) (log P(environment) = x(methanol) log P(methanol) + x(oils) log P(oils) + x(solvent) log P(solvent)) including reactants and organic solvent should be taken into account to consider the effect of the whole environment on lipase activity instead of just considering the effect of the organic solvent itself. Further study showed that the operational stability of the lipase could be improved significantly in this system and there was no loss in lipase activity even after its being continuously used for 200 batches. The phase diagrams of the ternary-components tert-butanol/methanol/rapeseed oils were plotted further, and it was found that the methanol tolerance was the saturated methanol concentration in the system. It was demonstrated first here that the improved stability of the lipase was due to the elimination of negative effects caused by methanol and byproduct glycerol in the tert-butanol system.