Akoh and co-workers have treated various types of TG with n-3 PUFA in lipase-
catalyzed transesterification reactions. These include incorporation of n-3 fatty acids
into vegetable oils (Huang and Akoh, 1994), melon seed oil (Huang et al., 1994),
trilinolein (Akoh et al., 1995), evening primrose oil (Akoh et al., 1996), borage oil
(Akoh and Moussata, 1998), and TG of medium-chain fatty acids, trilaurin, tricaprin
and tricaprylin (Lee and Akoh, 1996; 1998). In all cases it appears that the lipases
used (1,3-regiospecificRhizomucor mieheiand nonspecificCandida antarcticali-
pases) acted preferably at the 1,3-positions. This resulted in high incorporation levels
of the n-3 fatty acids into these positions, but high levels of n-3 fatty acids were also
incorporated into thesn-2 position, although lower. Other groups have also reported
on the incorporation of n-3 PUFA into various TG using lipase including borage oil
(Ju et al., 1998) and vegetable oils (Li and Ward, 1993b).
10.8 Concluding remarks
In this chapter the possibilities and advantages offered by lipases to the enrichment of
lipids with n-3 PUFA, EPA and DHA in particular, have been discussed. Lipases
already play an important role in the production of highly enriched concentrates
of EPA and DHA in the natural TG form. There are examples of industrial-scale
production involving lipase of such products of high quality and purity, which
are believed to be safer for human consumption than corresponding products
made chemically. The application of lipases to concentrate EPA and DHA up to
high purity levels has also been demonstrated. It is believed that such processes
may also soon be industrialized and will replace traditional physical methods
used to concentrate and purify EPA and DHA on a large scale.
From an industrial point of view, there are several important advantages offered by
lipases. They can be used without organic solvents, and this reduces the bulkiness of
such processes to a large extent. This is also important from the environmental and
explosion hazard points of view. The mildness offered by lipase is also very impor-
tant, not only in terms of energy cost (many lipase-promoted reactions can be run at
room temperature), but also from the quality point of view, as the n-3 PUFA are
186 10 Enrichment of Lipids with EPA and DHA by Lipase
Scheme 10. A two-step strategy to generate structured TG comprising EPA/DHA at the sn-2 position
and medium-chain fatty acids (MCFA) at the sn-1 and sn-3 positions.