Preparation of high-purity 1,3-distearoyl-2-oleoylglycerol (StOSt) via a two-step enzymatic interesterification combined with two-step solvent fractionation.

High-purity 1,3-distearoyl-2-oleoylglycerol (StOSt) was produced from high-oleic sunflower oil and ethyl stearate via a two-step enzymatic interesterification combined with a two-step solvent fractionation. Lipozyme RM IM (Rhizomucor miehei) was employed as a biocatalyst and the reaction was conducted in a packed-bed reactor. Molecular distillation was used to remove fatty acid ethyl esters from the reaction mixtures after enzymatic reactions. The optimum conditions were a temperature of 55 °C, a water content of 300 ppm (based on the total weight of the substrate), and a molar ratio of 1:8 (triacylglycerol (TAG) to ethyl stearate). The second enzymatic interesterification was carried out under the optimum conditions, resulting in the synthesis of 67.8 % StOSt-enriched TAG. To further enrich StOSt, two rounds of solvent fractionation were conducted using n-hexane and acetone, respectively. Consequently, StOSt TAG with a high purity of 83 % was achieved through the processes designed in this study.