Green synthesis of isopropyl palmitate using immobilized Candida antarctica lipase: Process optimization using response surface methodology

This work aims to produce isopropyl palmitate (IPP), a common emollient ester in a solvent-free system. An esterification reaction between isopropyl alcohol (IPA) and palmitic acid (PA) was performed in a closed batch reactor using immobilized Candida antarctica lipase as a biocatalyst. Reaction conditions were optimized using response surface methodology based on a five-level, three-variable composite design. The interactive effects of conditions on the IPP yield were investigated in the following ranges: IPA-to-PA molar ratio of 3:1–15:1, 1%–4% (w/w) Novozym 435, and 1%–10% (w/w) molecular sieves. The optimum conditions were IPA-to-PA molar ratio of 15:1, 4% w/w of Novozym 435, and 10% w/w of molecular sieves at 60°C and 150 RPM for 2.5 h. The maximum experimental and predicted conversion values were 90.00% and 90.92%, respectively. Moreover, Novozym 435 exhibited remarkable operational stability because it was used for 15 cycles without considerably losing its original activity. In studying the feasibility of the proposed method, a process flow diagram was suggested to perform the semicontinuous production of IPP in a solvent-free medium.