Lipase-catalyzed synthesis of kojic acid esters in organic solvents

Kojic acid is an inhibitor of bacteria, viruses, and fungi. It is used for inhibiting the browning effect of tyrosinase in the food and cosmetic indus tries. To improve its lipophilic properties, Pseudomonas cepacia lipase and Penicillium camembertii lipase were used for catalyzing the esterification of kojic acid to synthesize kojic acid monolaurate and kojic acid monoolea te. These products showed a 69.5% inhibitory effect on tyrosinase in hydrop hobic organic solvent. The yields of kojic acid esters were affected by enz ymes, substrates, organic solvent, and temperature. Lauric and oleic acids were the best substrates for esterification among various fatty acids teste d. CaCl2 and MnCl2 stimulate Pseudomonas cepacia lipase-catalyzed esterific ation by 7.0%. On the contrary, MgCl2, SrCl2, and ZnCl2 inhibited the react ion. The best pH of buffer for lipase pretreatment was pH 6.0. Pseudomonas and Penicillium lipases can be reused for the synthesis of kojic acid ester s. After reaction at 40 degrees C for 10 d, the Penicillium and Pseudomonas lipases still retained 57.0% and 92.0% of their initial activities, respec tively.