Biocatalyzed acidolysis of olive oil triacylglycerols with 9c,11t and 10t,12c isomers of conjugated linoleic acid

Abstract

Lipase catalyzed acidolysis of triacylglycerols (TAG) of olive oil with 9c,11t and 10t,12c isomers of conjugated linoleic acid (CLA) in an organic solvent was studied. The CLA isomers were first obtained in good yield starting from sunflower oil. The acidolysis reactions were carried out with two immobilized lipase, an sn-1,3-regiospecific one from Rhizomucor miehei and a nonregiospecific one from Candida antartica, in order to valuate not only the total incorporation of CLA isomers in olive TAG but also the distribution of the cited isomers in the three sn positions of TAG molecules. The effect of reaction time was also investigated; in fact two series of reactions, with the two lipases, were carried out for 24, 48 and 72 h. The TAG fractions relative to the starting olive oil TAG (OOTAG) and to the samples obtained from the acidolysis reactions were analyzed to obtain the total and positional fatty acid percentage compositions. The results show that after 24 h of reaction, high levels of CLA isomers were incorporated in OOTAG using Lipozyme IM and that slightly higher values were obtained by increasing the reaction time; Novozym 435 was less effective in catalyzing the incorporation of CLA isomers and CLA isomers were incorporated in OOTAG to a lesser degree. The results of stereospecific analysis of TAG fractions showed that, at every reaction time, the CLA isomers were incorporated mainly in sn-1 and sn-3 positions, as expected on the basis of the enzyme regiospecificity. As regards the TAG sn-2 position, the incorporation of CLA isomers was not observed after 24 h, but after 48 and 72 h; this occurrence was probably due to isomerization phenomena or regiospecificity loss after extended reaction times.