Synthesis of CLA-enriched TAG by Candida antarctica lipase under vacuum

Conjugated linoleic acid (CLA)-enriched triacylglycerol (TAG) of 90wt% was successfully synthesized in 10h by direct esterification of glycerol and CLA using an immobilized lipase from Candida antarctica under vacuum. The best operating conditions for the synthesis of TAG were investigated according to the three parameters of temperature, enzyme loading, and vacuum. The synthesis of TAG increased with increasing temperature but it did not significantly change above 60°C (p>0.05). The increase of enzyme loading lead to an enhanced conversion of TAG, but enzyme loading of more than 10% (based on the total weight of the substrates) was not effective. Moreover, when vacuum increased, the conversion of TAG increased, but the conversion rate decreased when the vacuum level was too high. The best combination of temperature, enzyme loading, and vacuum level were 60°C, 10% of the total weight of the substrates, and 0.4kPa, respectively. During the initial 6h of reaction, Candida antarctica lipase had more selectivity for 10t,12c-CLA than 9c,11t-CLA onto the glycerol backbone, and a preference for the incorporation at the sn-1,3 positions of glycerol rather than at the sn-2 position.