Lipase-catalyzed hydroesterification process for isopropyl palmitate synthesis from palm stearin

Abstract

In this study, isopropyl palmitate (IPP) was successfully prepared from palm stearin (PS) via a two-step lipase-catalyzed hydroesterification: (1) hydrolysis of PS in water and (2) esterification of the palmitic acid (PA) concentrate with isopropanol in a solvent-free system. Lewatit VP OC (LVO) 1600-immobilized Eversa Transform (ET) 2.0 was used as the biocatalyst in both reaction steps. The fixation level of proteins contained in ET 2.0 solution with a protein concentration of 34.7 mg/mL on LVO 1600 and the quantity of the proteins bound to LVO 1600 were 78.8 wt% and 214.5 mg per gram of the support material, respectively. The first-step reaction yielded a free fatty acid (FFA) fraction containing 99.4 area% FFAs using reaction conditions of 50 °C, 1:80 (PS-to-water molar ratio), 10 mg/g PS (enzyme loading), and 24 h (reaction time). Fractional crystallization of the FFA fraction in n-hexane for 2 h (crystallization time) at − 5 °C yielded a PA concentrate containing 91.0 wt% PA. Finally, a 90.1 area% conversion to IPP was achieved in the second-step reaction under reaction conditions of 55 °C, 1:1.5 (PA concentrate-to-isopropanol molar ratio), 20 mg/g total substrates (enzyme loading), and 24 h (reaction time).