8.2.2 Production of GLA-rich oil from borage oil
Candidalipase acts on GLA as weakly as on DHA, and GLA-rich oil can be pro-
duced by selective hydrolysis of borage oil (Syed Rahmatullah et al., 1994; Shimada
et al., 1998b). Borage oil (initial GLA content, 22 wt%) was hydrolyzed at 35 8 C for
15 min to 24 h with 100 U g–1reaction mixture ofCandidalipase. Figure 3 shows the
correlation between the hydrolysis extent and the GLA content in glycerides. Unlike
enrichment of DHA in selective hydrolysis of tuna oil (see Figure 2), the GLA con-
tent was not raised over 46 % at above 65 % hydrolysis (Figure 3). The reaction
conditions for the efficient enrichment of GLAwere as follows: a mixture of borage
oil, 50 % water, 20 U g–1mixture ofCandidalipase was incubated at 35 8 C for 16–
24 h with stirring. The enzyme amount was one-tenth of that for the hydrolysis of
tuna oil, showing that borage oil was a better substrate for the lipase than tuna oil.
8.2.3 Production of AA-rich oil from AA-containing single cell oil
Any oils and fats from plants and animals do not contain high content of AA. Yamada
et al. (1988) found thatMortierellaaccumulated AA-containing triglycerides in the
mycelia, and the single cell oil containing 25 % to 40 % AA has been produced
industrially (Shinmen et al., 1989; Higashiyama et al., 1998). BecauseCandidali-
pase also acted on AA very weakly, we attempted to enrich AA in glycerides by
selective hydrolysis of 25 % AA-containing oil (TGA25; Suntory, Osaka, Japan).
A mixture of TGA25 oil, 50 % water, and 90 U g–1mixture ofCandidalipase
was incubated at 35 8 C for 16 h with stirring. The resulting glycerides contained
50 % AA at 52 % hydrolysis. To further increase the AA content, glycerides
were extracted from the reaction mixture withn-hexane, and hydrolyzed again un-
der the same conditions. The extents of the second and third hydrolyses reached 18 %
and 17 %, respectively, and the three-time repetitions raised the AA content to 60 %
with a 75 % recovery (Table 1) (Shimada et al., 1995b).
8.2 Production of PUFA-rich oils by selective hydrolysis 131
Figure 3. Correlation between hydrolysis extent of borage oil and GLA content in undigested glyc-
erides. Borage oil was hydrolyzed at 35 8 C for 0.25 to 24 h in a mixture containing 50 % water and
with 100 U g–1mixture ofCandida rugosalipase.