Novel Strategy for Synthesis of Stearidonic Acid Enriched Triacylglycerol from Ahiflower Seed Oil via a Two-step Enzyme Reaction

Abstract

Stearidonic acid (SDA) is a plant-based n-3 polyunsaturated fatty acids (PUFAs) with several positive therapeutic effects on human health such as reducing risks of cardiovascular diseases, obesity, inflammation, and cancer. Moreover, the conversion efficiency of SDA to EPA is significantly higher than α-linolenic acid to EPA, in the human body. Plant oils with SDA, such as ahiflower seed oil and echium seed oil, exhibit substantially higher oxidative stability than fish oil with EPA and DHA, the most popular n-3 PUFA. The present study has successfully carried out the enrichment of SDA and the synthesis of triacylglycerol (TAG) consecutively via two lipase-catalyzed reactions, which are selective hydrolysis and esterification, while most of n-3 PUFAs studies have separately employed its enrichment and the synthesis of TAG. SDA was enriched into a glyceride fraction from ahiflower seed oil by Candida rugosa lipase-catalyzed selective hydrolysis, and the SDA-enriched glycerides were separated from the reaction mixture using molecular distillation. SDA was enriched up to 40.7 mol% in glyceride fraction from an initial value of 21.6 mol% under the optimum conditions of 35 oC, and 0.1% enzyme loading relative to the weight of the total substrate. Then, SDA-enriched TAG was synthesized from the SDA-enriched glycerides and the fatty acid obtained from part of the SDA-enriched glycerides by saponification via esterification using an in-house immobilized lipase as a biocatalyst. The in-house immobilized lipase was prepared from Eversa® Transform 2.0 (liquid form) using Lewatit VP OC 1600 as a carrier. The maximum TAG yield of ca. 94% was achieved after 12 h under the optimum conditions, which are the temperature of 50 oC, the enzyme loading of 10 % relative to the weight of the total substrate, and the vacuum of 10 torr."