Optimisation of kojic acid monolaurate synthesis with lipase PS from Pseudomonas cepacia

To improve the instability of kojic acid in food and cosmetic use, the esterification of kojic acid catalysed by lipase from Pseudomonas cepacia (Amano PS) to synthesise kojic acid monolaurate (KAML) was investigated in this study. Response surface methodology (RSM) with a five-level/five-factor central composite rotatable design (CCRD) was employed to evaluate the effects of synthesis parameters such as reaction time (8-24h), temperature (35 55 degreesC), enzyme amount (10-50%), substrate molar ratio of lauric acid to kojic acid (1:1-3:1) and added water content (0-20%) on the percentage molar conversion to KAML by direct esterification. Reaction time and added water content were the most important variables, while substrate molar ratio had less effect on percentage molar conversion. Based on canonical analysis and ridge maximum analysis, optimal synthesis conditions were reaction time 19h, temperature 44 degreesC, enzyme amount 38%, substrate molar ratio 2:1 and added water content 10%. The predicted value was 85% and the actual experimental value 82% molar conversion. (C) 2002 Society of Chemical Industry.