Cleaner Production of Isopropyl Laurate using Lipase Catalyzed Esterification: Optimization by Response Surface Methodology

Abstract

This work aims to produce a common emollient ester isopropyl laurate (IPL) in a solvent-free system. Isopropyl alcohol (IPA) and lauric acid (LA) were esterified in a closed batch reactor, employing immobilized Candida antarctica lipase as a biocatalyst. Response surface methodology was based on a five-levels, three variables composite design was used to optimize the reaction conditions. The interactive effect of three different parameters on isopropyl laurate (IPL) synthesis was studied. The following conditions' ranges were considered: molecular sieves of 1%–10% (w/w), IPA-to-LA molar ratios of 3:1–15:1, and enzyme load of 1%–4% (w/w). As a result of the optimization study, the optimum conditions were 4% w/w of Novozym 435, 15:1 IPA: LA molar ratio, and 10% w/w molecular sieves at 150 RPM, 60°C and for 2.5 h. The RSM study showed that the maximum predicted and experimental conversion values were 90.75 and 91%, respectively. It is worth mentioning that Novozyme 435 demonstrated superior operational stability, where it was used for 15 cycles without significant denaturation. The clean nature of the proposed method and the proven operational stability of Novozym 435 reveal this approach's technical and economic feasibility.