Enzymatic synthesis and characterization of structured lipids: Medium- and long-chain triacylglycerols enriched with lauric acid and diverse long-chain fatty acids

In this study, medium- and long-chain triacylglycerol (MLCT) structured lipids were synthesized by lipase catalyzed acidolysis of lauric acid (La) with four kinds of common edible oils of different fatty acid compositions, including palm oil (PO), camellia oleifera seed oil (CSO), soybean oil (SO) and flaxseed oil (FO). The lipases and reaction conditions including substrate molar ratio, reaction temperature, time and enzyme loading) were optimized. The physicochemical properties of their MLCT products were determined. Moreover, the interaction mechanism between lipase and different MLCT molecules was revealed. The obtained optimum conditions were as follows: substrate molar ratios of 3:1 (La/oil) for FO, SO, and CSO, 7:1 for PO; enzyme loading of 8%, reaction temperature of 50 degrees C, and reaction time of 6 h for PO, 4 h for SO and 3 h for CSO and FO. Under the conditions, the product based on PO had the highest La content (40.37%) and MLCT yield (94.85%), followed by FO and SO, (29.86%, 29.71% and 88.41%, 87.55%, respectively), least on CSO (25.40% and 81.79%). The lipase established hydrogen bonds and hydrophobic interactions with triacylglycerol ligands. Triacylglycerol 1(3),2-Linolenin-3(1)Laurin (LnLnLa, specific in FO-MLCT) exhibited strongest binding activity with Lipozyme RM. Compared with substrate oils, the corresponding MLCT structured lipids showed improved thermal behavior and significant differences in the crystallization temperature as a result of acidolysis esterification. This study developed diverse MLCTs with La, and provided an in-depth understanding of the relationships between substrate composition, interaction, and MLCT structured lipids.