Enzymatic esterification of (-)-menthol with fatty acids in solvent by a commercial lipase from Candida rugosa

Esterification of (-)-menthol with fatty acids in isooctane was successfully catalyzed using a commercial lipase, Lipase AY 'Amano' 30 from Candida rugosa in original powder form. The esterification reactions were performed to elucidate the effects of temperature, enzyme load, molar ratio of (-)-menthol/fatty acid, and fatty acid type, keeping the (-)-menthol concentration at 200 mM. At the optimal conditions for (-)-menthol esterification, determined at a (-)-menthol/lauric acid molar ratio of 1:1 and 35°C [1.5 g enzyme/g (-)-menthol, 0.1 g molecular sieves], the molar conversion of (-)-menthol after 48 h reached 93%. After 24 h, the lowest and the highest molar conversions of fatty acids at 2:1 molar ratio were obtained with myristic acid (71%) and margaric acid (98%), respectively. After 48 h, the molar conversions of lauric acid at molar ratios 2:1, 1:1, and 1:2 were 98, 93, and 49%, respectively.