Front Matter

in activity was due to the inactivation of the lipase or its removal from the ceramic

carrier, and not to the release of water bound to the immobilized lipase.

8.3.4 Production of structured lipids containing linolenic,

aa-linolenic acids and CA

When safflower and linseed oils were acidolyzed with CA under the conditions

similar to those in the acidolysis of tuna oil with CA, the structured lipids containing

linoleic anda-linolenic acids were also produced efficiently (Shimada et al., 1996b).

Rhizopuslipase acted on safflower and linseed oils more strongly than on tuna oil,

and approximately 70 % of the fatty acids at the 1,3-positions of the oils were ex-

changed for CA after 15 h (the CA content in triglycerides was 47 mol%). To in-

vestigate the stability of immobilized lipase, acidolysis was repeated by transferring

the immobilized lipase to a fresh substrate mixture every 2 days. In the reactions of

safflower and linseed oils, the enzyme could be used for 45 and 55 cycles, respec-

tively. These results showed that our reaction system was very effective for the pro-

duction of MLM-type structured lipids from natural oils. In this study, we usedRhi-

zopuslipase immobilized on the ceramic carrier. CommercialRhizomucor miehei

lipase (Lipozyme IM60; Novo Nordisk, Bagsvaerd, Denmark) is a 1,3-positional-

specific lipase, and has been used by many researchers. MLM-type structured lipids

were efficiently produced under the same conditions using the lipase, and this en-

zyme had an advantage that pretreatment in a reaction mixture with a small amount

of water was not necessary for its activation.

8.3.5 Continuous production of a structured lipid containing GLA

and CA by fixed-bed reactor

A batch reaction with immobilizedRhizopuslipase was effective to produce MLM-

type structured lipids from natural oils and CA. A reactor with an impeller has been

generally used for industrial batch reaction, but has the risk that the carrier of im-

mobilized enzyme is destroyed by mechanical agitation. Because the drawback can

be avoided by flow reaction with a fixed-bed reactor, we attempted the production of

MLM-type structured lipid containing GLA by a continuous flow reaction (Shimada

et al., 1999b). The scheme of the reactor used in this study is shown in Figure 6.

ImmobilizedRhizopuslipase required the pretreatment in a mixture containing a

small amount of water for its activation. Thus, immobilized lipase (8 g) was sus-

pended in water-saturated substrate mixture of borage oil/CA (1 : 2, w/w; water con-

tent, 1.18 %), and then packed into a column (1562 mm). A substrate mixture

saturated with water (100 mL) was fed into the column at 30 8 C and a flow rate

of 4.5 mL h–1(4.1 g h–1) for the activation of lipase, and the mixture without adding

water (water content, 350–500 ppm) was then fed under the same conditions (Figure

7). As a result, the incorporation of CA into triglycerides reached 54 mol%, and the

content of partial glycerides in the glyceride fraction was below 1.5 wt%. The CA

8.3 Production of highly absorbable structured lipid 139