Production of High-Purity 1,3-Distearoyl-2-Oleoylglycerol via Repeated Enzymatic Reaction Combined with Solvent Crystallizations

High-purity 1,3-distearoyl-2-oleoylglycerol (StOSt) was produced from high-oleic sunflower oil and ethyl stearate via repeated lipase-catalyzed interesterification combined with a two-step solvent crystallization. Lipozyme RM IM (Rhizomucor miehei), a sn-1,3-specific lipase, was employed as the biocatalyst and a reaction was conducted in a packed bed reactor. Molecular distillation was used to remove fatty acid ethyl ester from the reaction mixture after enzymatic reaction. The effects of temperature, water content, and molar ratio were studied in the first enzymatic reaction. 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 to ethyl stearate), respectively. The repeated enzymatic reaction was carried out under the optimum conditions, resulting in the synthesis of 66% StOSt-rich fats. To further concentrate StOSt from the enzymatically derived StOSt-rich fats, two rounds of solvent crystallization were conducted using n-hexane and acetone. Consequently, high-purity StOSt with 90% purity was achieved through the processes designed in this study.