Abstract
The effect of chain length, number of double bonds, the location and geometry of double bonds, the reaction conditions, and reactivity of different lipases on the incorporation of selected long-chain fatty acids (LCFA) into triacylglcerols, such as trilinolein (tri C18:2) and trilinolenin (tri C18:3) is examined. This study also discusses reasons behind different degrees of incorporation of selected LCFA into tri C18:2 or tri C18:3 on a molecular basis. Five lipases, namely
Candida antarctica (Novozyme-435),
Mucor miehei (Lipozyme-1M),
Pseudomonas sp. (PS-30),
Aspergillus niger (AP-12), and
Candida rugosa (AY-30) were screened for their effect on catalyzing the acidolysis of trilinolein (tri C18:2) or trilinolenin (tri C18:3) with selected C18, C20 and C22 fatty acids (FA). Incorporation of a mixture of C18 FA into trilinolein, using
Pseudomonas sp., the most effective lipase, was in the order of SA
>
OA
>
GLA
>
ALA
>
CLA. Meanwhile, the degree of n-6 FA incorporation into tri C18:2 with
Pseudomonas sp. was in the order of GLA
>
AA
>
CLA. The order of incorporation of n-3 FA into trilinolein using lipases from
C. antarctica and
M. miehei was ALA
>
EPA
>
DPA
>
DHA.
Lipases from
M. miehei and
Pseudomonas sp. catalyzed better incorporation of a mixture of C18 FA into tri C18:3 while the remaining lipases catalyzed slight incorporation (⩽1%) of these FA into this oil. SA and CLA were the most and least reactive C18 FA, respectively. EPA was better incorporated into trilinolenin than DPA or DHA using the enzymes selected. Lipases from
Pseudomonas sp.,
C. rugosa, and
M. miehei catalyzed better the incorporation of a mixture of equimole quantities of n-6 FA into tri C18:3 than any of the other lipases tested; the lowest incorporation (⩽1%) was observed using
Candida antarctica and
A. niger, possibly due to the experimental conditions employed in this study which were suitable for these enzymes. The degree of incorporation of EPA into tristearin (tri C18:0), triolein (tri C18:1), and trilinolenin (tri C18:3) decreased as the number of double bonds increased from zero in tristearin to nine in trilenolenin. The same trends were observed for ALA and DHA.