ably) EPA-deficient 1-LPC dominate in the reaction mixture during the early stages
of the reaction, whereas at the later stage highly EPA-enriched 2-LPC and PC be-
come dominant.
10.6 EPA and DHA concentrates from fish oils by lipase
Based on their fatty acid selectivity and discrimination against n-3 PUFA, lipases can
be used as an alternative means of concentrating EPA and DHA in fish oils by kinetic
resolution. There are numerous reports in the literature describing the application of
lipase to concentrate EPA and DHA in fish oils (Haraldsson et al., 1997). The reac-
tions involved include hydrolysis and alcoholysis of TG and monoesters, direct es-
terification of free acids with alcohols, and various transesterification reactions. In
this respect lipases can be divided into three categories: (i) those which display no or
very low activity toward fish oils or fish oil fatty acids as substrates; (ii) those dis-
criminating against n-3 fatty acids and can be used to concentrate EPA and DHA
together; and (iii) those which offer a strong discrimination between EPA and
DHA, usually in favor of EPA. The lipases belonging to the third group can be
used to concentrate EPA and/or DHA individually.
The lipases belonging to the first group clearly offer very little application in the
fish oil field. The lipases in the second group act very well on the bulk of saturated
and monounsaturated fatty acids present in the fish oil, leaving EPA and DHA largely
10.6 EPA and DHA concentrates from fish oils by lipase 183
Scheme 7. A proposed simplified reaction pathway for lipase-catalyzed acidolysis of PC with EPA. For
abbreviations see Scheme 1.