It is interesting to note that selective hydrolysis of fish oil triglycerides leads to
unexpectedly high residual levels of triglyceride, even at degrees of conversion
above 70 % (Tanaka et al., 1992; Moore and McNeill, 1996). It is believed that
Candida rugosalipase recognizes the whole triglyceride structure and discriminates
more strongly against triglycerides containing increasing numbers of LCPUFA. This
‘compositional specificity’ has been studied using chemically synthesized triglycer-
ides comprising only of oleic acid or DHA (Tanaka et al., 1993). The selectivity was
less in the case of diglycerides, and monoglycerides were hydrolyzed relatively ea-
sily. This results in the triglyceride becoming the dominant species.
Awider range of lipases has been used for selective (trans)esterification using fish
oil fatty acids as starting material. This overcomes the problems associated with 1,3-
regioselective lipases (see above) as simple aliphatic alcohols can be used (e.g.
methanol, ethanol,n-butanol). The desired LCPUFA is concentrated in the fatty
acid fraction and the esters of other fatty acids are removed by distillation. Examples
of lipases used include:Rhizopus arrhizus,Rhizomucor miehei(Mukherjee et al.,
1993),Rhizopus delemar(Shimada et al., 1997), andPseudomonassp. (Breivik
et al., 1997; Haraldsson et al., 1997).
Separation of CLA isomers
Conjugated linoleic acid (CLA) is used as a general term to describe a family of
compounds derived from linoleic acid (C18 : 2, n-6) containing conjugated double
bonds. These double bonds can occur in either thecisortransconfiguration.
CLA occurs naturally in meat and dairy products obtained from ruminant animals
where the predominant isomer (>75 %) isc-9,t-11 CLA (Chin et al., 1992; Lin et
al., 1995). Anti-cancer activity associated with beef has been attributed to the pre-
8 1 The Exploitation of Lipase Selectivities for the Production of Acylglycerols
Figure 1. Surface active compounds from plant materials.