Lipase-catalyzed synthesis of structured triacylglycerides from 1,3-diacylglycerides

摘要

A new method for the lipase-catalyzed synthesis of structured TAG (ST) is described. First, sn1,3-dilaurin or-dicaprylin were enzymatically synthesized using different published methods. Next, these were esterified at the sn2-position with oleic acid or its vinyl ester using different lipases. Key to successful enzymatic synthesis of ST was the choice of a lipase with appropriate FA specificity, i.e., one that does not act on the FA already present in the sn1,3-DAG, but that at the same time exhibits high selectivity and activity toward the FA to be introduced. Reactions were performed in the presence of organic solvents or in solvent-free systems under reduced pressure. With this strategy, mixed ST containing the desired compounds 1,3-dicaprylol-2-oleyl-glycerol or 1,3-dilauroyl-2-oleyl-glycerol (CyOCy or LaOLa) were obtained at 87 and 78 mol% yield, respectively, using immobilized lipases from Burkholderia cepacia (Amano PS-D) in n-hexane at 60°C. However, regiospecific analysis with porcine pancreatic lipase indicated that in CyOCy, 25.7% caprylic acid and in LaOLa 11.1% lauric acid were located at the sn2-position. Oleic acid vinyl ester was a better acyl donor than oleic acid. Esterification of sn1,3-DAG and free oleic acid gave very low yield (<20%) of ST in a solvent system and moderate yield (>50%) in a solvent-free system under reduced pressure.