Front Matter

including ether-type PL and plasmalogens. This again is based on lipase enantio-

selectivity. There are several reports in the literature of kinetic resolution of race-

mates or biotransformations involving prochiral glycerol derivatives. Again, lipases

can be used to introduce EPA or DHA at a later stage in the synthesis.

From what has been discussed above it is clear that the possibilities of employing

lipases in the field of lipids and n-3 PUFA are virtually endless. In what follows in

this chapter the application of lipases to produce various lipid classes highly enriched

with EPA and DHA including TG, EL and PL will be described. The application of

lipases to concentrate EPA and DHA from fish oil will also be described. Finally, the

application of lipases to produce structured lipids containing EPA and DHA will be

discussed briefly.

10.3 Enrichment of triacylglycerols with EPA and DHA

This Section is divided into two parts. The first part deals with incorporation of EPA

and DHA into fish oil by lipase-catalyzed transesterification reactions. The second

part involves the direct esterification of glycerol with PUFA as free acids to obtain

TG of identical composition to the PUFA being used by a different lipase. That

methodology also offers homogeneous TG of 100 % EPA and 100 % DHA.

10.3.1 Enrichment of cod liver oil with EPA and DHA

It is relatively easy to concentrate EPA and DHA up to high levels as free fatty acids

or monoesters. However, the natural form of these fatty acids in fish oil is TG, and the

major challenge was to produce natural TG highly enriched with EPA and DHA, far

beyond the 30 % level mentioned earlier. A highly successful solution to that pro-

blem was based on treating cod liver oil with free fatty acid or monoester concen-

trates of EPA and DHA in the presence of lipase to effect fatty acid exchange be-

tween the natural TG and the concentrates (Haraldsson et al., 1989). From the mar-

keting point of view it was also important that cod liver oil already had a long history

(decades) on the market as a vitamin A and D supplement (Hjaltason, 1989), and that

the product could be claimed as being derived directly from cod liver oil.

Lipozyme, the immobilized 1,3-regiospecific lipase from the fungusMucor (Rhi-

zomucor) miehei(available commercially from Novo Nordisk in Denmark), was

employed to effect transesterification reactions of cod liver oil with concentrates

of EPA and DHA. The cod liver oil comprised approximately 9–10 % each of

EPA and DHA, and TG highly enriched with n-3 PUFA was accomplished, of

high purity and in virtually quantitative yields. Interesterification and acidolysis

reactions with ethyl ester and free fatty acid concentrates, respectively, both com-

prising 85 % EPA + DHA content, resulted in TG containing 60–65 % EPA+DHA

and well over 70 % total n-3 PUFA. At that time this represented by far the highest

EPA- and DHA-enriched TG product available. Both reactions were conducted in the

absence of any solvent, using 10 % dosage of lipase, as based on the weight of fat, at

10.3 Enrichment of triacylglycerols with EPA and DHA 173