Front Matter

fication reactions (Rangheard et al., 1989). In hydrolytic reactions catalyzed by li-

pases fromR. arrhizusand porcine pancreas discrimination againstcis-6-18 : 1

(Mbayhoudel and Comeau, 1989) and n-3 22 : 6 (Yang et al., 1990) moieties, respec-

tively, has been observed. Similarly, lipase from rape hydrolyzes tripetroselinin and

tri-c-linolenin at much lower rate than triolein (Hills et al., 1990a).

It appears from the above findings that discrimination against fatty acids having

the first double bond from the carboxyl end as acis-4,cis-6 or acis-8 is a common

feature of many lipases. It has been suggested that the lipase from rape discriminates

againstanti-orientedcis-4 andcis-6 unsaturated fatty acids due to the direction of

twist of the carbon chain after the first double bond which might hinder binding of

the reactive group to the lipase (Hills et al., 1990a). It is conceivable that the same

argument is valid for the selectivity of many lipases against fatty acids having acis-4,

cis-6 or acis-8 double bond as the first olefinic bond at the carboxyl end of the fatty

acid.

In the esterification of common and unusual fatty acids withn-butanol, lipases

from rape, porcine pancreas,C. rugosa, R. mieheiandR. arrhizus(Jachmania ́n

et al., 1996), papaya (Mukherjee and Kiewitt, 1996b) and pineapple as well asRhi-

zopussp. (Mukherjee and Kiewitt, 1998) have been shown to have strong preference

for fatty acids having hydroxy groups, e.g., ricinoleic (12-hydroxy-cis-9-octadece-

noic) and 12-hydroxystearic acid, epoxy groups, e.g.trans-9,10-epoxystearic acid,

and cyclopentenyl fatty acids having saturated alkyl chains, e.g. hydnocarpic

[11-(cyclopent-2-en-1-yl)undecanoic] and chaulmoogric [13-(cyclopent-2-en-1-

yl)tridecanoic] acid, whereas a cyclopentenyl fatty acid having acis-6 olefinic

bond, i.e., gorlic [13-(cyclopent-2-en-1-yl)tridec-6-enoic] acid is strongly discrimi-

nated against by several lipases (Jachmania ́n et al., 1996; Jachmania ́n and Mukher-

jee, 1996).

A partially purified lipase fromVernonia galamensisseeds has been shown to

catalyze the hydrolysis of trivernolin (tri-cis-12,13-epoxy-cis-9-octadecenoin), the

predominant constituent of the seed oil ofV. galamensis, much faster than triolein

or other triacylglycerols (Ncube et al., 1995). Similarly, in the transesterification of

tricaprylin with fatty acids, catalyzed by purifiedV. galamensislipase, a strong pre-

ference for vernolic (cis-12,13-epoxy-cis-9-octadecenoic) acid has been observed

(Ncube et al., 1995).

The above substrate specificities of various lipases have been utilized for the

enrichment of specific unsaturated fatty acids or derivatives via kinetic resolution

from their mixtures, obtained from naturally occurring fats and other lipids.

2.2.2 Enrichment of n-6 polyunsaturated fatty acids

The applications of lipase-catalyzed kinetic resolution for the enrichment of n-6

polyunsaturated fatty acids are summarized in Table 2.

c-Linolenic acid is of considerable commercial interest due to its beneficial bio-

medical properties (Horrobin, 1992). Seed oils of evening primrose,Oenothera bi-

ennis(Hudson, 1984; Mukherjee and Kiewitt, 1987), borage,Borago officinalis

(Whipkey et al., 1988) andRibesspp. (Traitler et al., 1984) are some common

2.2 Fractionation of fatty acids and other lipids by lipase-catalyzed reactions 29