Surfactant‐Coated Lipase Suitable for the Enzymatic Resolution of Menthol as a Biocatalyst in Organic Media

Enantioselective esterification of menthol with fatty acids using a surfactant‐coated lipase was carried out in organic media. The surfactant‐coated lipase originating from Candida cylindracea appeared to be highly enantioselective and good biocatalyst for the resolution of racemic menthol. The enzymatic activity of the lipase in organic media was significantly increased by a coating with a nonionic surfactant. The reaction rate of the coated lipase was more than 100 times that of the powder lipase. In order to investigate the effect of the organic solvent on enantioselectivity, 19 kinds of solvents were employed. The nature of the organic solvent strongly affected the efficiency of the biocatalyst and the enantioselectivity. Among them, isooctane was the best organic solvent from the viewpoint of reaction rate and enantioselectivity. The effect of reaction temperature on esterification was also investigated. The optimal reaction temperature was around 35 °C. The enzymatic activities using n‐saturated fatty acids with different alkyl chain lengths were compared, and long‐chain fatty acids were found to be better substrates than shorter ones. The relationship between the initial rate of the esterification and the carbon number of the fatty acid was not linear. These results suggest that there are inherent Km values for each fatty acid.