Lipase-catalyzed synthesis of isosorbide monoricinoleate: process optimization by response surface methodology

A new ester of natural origin was prepared by esterification of 1,4:3,6-dianhydro-d-glucitol (isosorbide) with a long-chain fatty acid (ricinoleic), using immobilized enzyme catalyst in non-solvent system. Renewable raw materials produced from carbohydrates and oil biorefineries were used as basic substances in this study. Response surface methodology (RSM) based on central composite design was used to optimize the main important reaction variables - catalyst concentration (2.2-7.8%) wt and temperature (60-80 degrees C). Using RSM, quadratic model was developed to correlate the preparation variable to the responses (isosorbide mono- and diricinoleate yield). It was found that the most effective parameter was temperature. The optimum combination derived via RSM for producing the high monoester yield (93%) and low diester yield (1.7%) was found to be 6.2% wt catalyst concentration at a reaction temperature of 63 degrees C during 2h of reaction time.