Enzymatic purification of polyunsaturated fatty acids

Polyunsaturated fatty acids (PUFAs) have various physiological functions. O f these, ethyl eicosapentaenoate is industrially purified and used as a med icine. Other PUFAs, such as docosahexaenoic acid (DHA), gamma -linolenic ac id (GLA), and arachidonic acid (AA), are also expected to be used as pharma ceutical agents; however, their industrial purification processes have not been established. Because PUFAs are highly unstable against heat and oxidat ion, we attempted to purify them by taking advantage of their enzymatic rea ctions. When free fatty acids (FFAs) originating from PUFA-containing oil w ere selectively esterified with lauryl alcohol (LauOH) using a lipase actin g on a desired PUFA very weakly, the PUFA was efficiently enriched in the F FA fraction. In addition, when selective alcoholysis of ethyl esters origin ating from PUFA-containing oil with LauOH was carried out, the PUFA ethyl e ster (EtPUFA) was enriched to a desired purity in the unreacted ethyl ester fraction. These reaction mixtures contain LauOH, PUFA (EtPUFA), and lauryl esters, and their molecular weights are different from one another. Hence, PUFA or EtPUFA can be easily separated by conventional distillation. Selec tive esterification increased the purity of DHA, GLA, and n-6 PUFAs rich in AA to 91, 98, and 96 wt%, respectively. Selective alcoholysis was also eff ective for increasing the purity of ethyl docosahexaenoate to 90 wt%.