Optimization of lipase-catalyzed synthesis of ß-sitostanol esters by response surface methodology.

The esters of ß-sitostanol and fatty acids are known for their effect as cholesterol-lowering agents. In this work, the efficiency of three lipases as biocatalysts of the esterification of ß-sitostanol and C16 and C18 fatty acids was compared. The sterol esterase of Ophiostoma piceae (OPEr) yielded the highest esterification rates and was selected for further optimization of the reaction. The effects of four parameters (temperature, enzymatic dosage, acyl donor concentration, and reaction time) on ester synthesis were investigated and the process conditions were optimized using response surface methodology (RSM). The best conditions for esterification for each fatty acid were predicted using a second-order model, and experimentally validated. Very high esterification efficiencies (86-97%) were observed using the predicted values for the four variables. This approach was shown to be suitable for optimizing the enzymatic production of ß-sitostanol esters, which represents a green alternative to the chemical synthesis of these dietary complements.