nating seeds have unusual fatty acid selectivities with strong preference for the domi-
nant fatty acid(s) present in the seed. Examples include; castor bean lipase with a
preference for ricinoleic acid (Lin et al., 1986); oil palm lipase (Lin et al., 1986), elm
lipase (Lin et al., 1986) andCuphealipases (Hellyer et al., 1999) for capric acid, and
Vernonialipase for vernolic acid (Ncube et al., 1995). The majority of other seed
lipases studied are non-selective, i.e. they are able to act on a wide range of common
fatty acids, even if the fatty acid is not normally present in the seed. Although the
lipase obtained from oilseed rape (Brassica napus) is non-selective towards a wide
range of common fatty acids it has been shown to discriminate againstcis-4 andcis-6
unsaturated fatty acids (Hills et al., 1990a). Some of the selectivities reported are also
dependent on the variety used; this is illustrated byCuphealipases. The lipase ob-
tained fromCuphea racemosawas found to be non-selective, whereas those obtained
fromCuphea procumbensandCuphea llaveaboth showed approximately 20-fold
preference for capric acid over other fatty acids (Hellyer et al., 1999).
One drawback to the application of plant lipases is that they are usually only
present at very low levels in germinating seeds; castor bean lipase is one of the
few present in dormant seed. Consequently there are few examples of their use
as biocatalysts. However, de-fatted oat caryopses have been used for the hydrolysis
of edible oils (Piazza, 1991) and oilseed rape lipase has been used for the enrichment
of GLA from evening primrose oil (EPO) (Hills et al., 1990b). The esterification of
EPO fatty acids withn-butanol was conducted at 30 8 C with immobilized oilseed
rape lipase and resulted in an approximately 7-fold enrichment of GLA in the re-
sidual fatty acid fraction (65 % from 10 % in starting oil).
10 1 The Exploitation of Lipase Selectivities for the Production of Acylglycerols
Figure 2. Surface active compoundsviaenzymatic acyl transfer.