Control of water activity in lipase catalysed esterification of chiral alkanoic acids

Candida rugosa lipase (CRL) catalysed enantioselective esterification of racemic 2-methylhexanoic acid was performed with 1-decanol in organic solvent at constant water activity (aw). The aw was maintained either by a salt hydrate pair added in the reaction mixture or by performing the reaction in an air tight desiccator over an aqueous saturated salt solution. It was found that the enatiomeric ratio and average reaction rate profiles were similar when controlling the water activity for the esterification reaction with these two different methods. But, in some cases the average rate of the reaction and the enantioselectivity of CRL was affected when ions from the salt hydrate pairs were present in the reaction mixture.