Enzymatic epoxidation of Sapindus mukorossi seed oil by perstearic acid optimized using response surface methodology

As a novel renewable resource, Sapindus mukorossi seed oil (SMSO) with an iodine value of 84.86 g/100 g, and containing 51.0 ± 0.9% oleic acid (18:1), 6.6 ± 0.6% linoleic acid (18:2), 1.1 ± 0.3% linolenic acid (18:3), and 23.1 ± 0.9% eicosanoic acid (20:1), was epoxidized using hydrogen peroxide as oxygen donor and stearic acid as active oxygen carrier in the presence of immobilized Candida antarctica lipase B. The effect of the amount of stearic acid on the enzymatic epoxidation was investigated. Response surface methodology (RSM) was used to study and optimize the effects of variables (reaction temperature, enzyme load, mole ratio of H2O2/CC-bonds, and reaction time) on the epoxy oxygen group content (EOC) of epoxidized SMSO. Results showed that stearic acid as active oxygen carrier could enhance the enzymatic epoxidation of SMSO. The variables of reaction temperature and enzyme load were the most significant in the process. A two second-order model was satisfactorily fitted the data (R2 = 0.9723) with non-significant lack of fit. The optimum EOC of epoxidized SMSO was 4.6 ± 0.3% under the conditions of 50.0 °C, 7.0 h, 2.00% (relative to the weight of SMSO) enzyme load, and 4:1 mole ratio of H2O2/CC-bonds.

Research highlights
► Sapindus mukrossi seed oil (oleic acid 51.0 ± 0.9%, linoleic acid 6.6 ± 0.6%, arachidic acid 7.3 ± 0.3%, eicosanoic acid 23.1 ± 0.9%) was epoxidized using hydrogen peroxide as oxygen donor and stearic acid as active oxygen carrier in the presence of Novozym 435.
► The maximum epoxy oxygen group content (4.6 ± 0.3%,) of epoxidized SMSO was obtained as follows: 50.0 °C, enzyme load 2.00% (relative to the weight of SMSO), 4:1 of mole ratio of H2O2/CC-bonds for 7.0 h.