In general, TAGs are mostly synthesized in the light, stored in cytosolic lipid bodies, and then reutilized
for polar lipid synthesis in the dark. Microalgal TAGs are
generally characterized by both, saturated and
monounsaturated FAs. However, some oil-rich species
have demonstrated a capacity to accumulate high levels of
long-chain polyunsaturated fatty acids (PUFA) as TAG
(Alonso et al., 1998). A detailed study on both
accumulation of TAG in the green microalga
Parietochloris incisa and storage into chloroplastic lipids
(following recovery from nitrogen starvation) led to the
conclusion that TAGs may play an additional role ahead of
being an energy storage product in this alga(Khozin-
Goldberg and Cohen, 2006). Hence, PUFA-rich TAGs are
metabolically active and are suggested to act as a reservoir
for specific fatty acids. In response to a sudden change in
the environmental condition, when the de novo synthesis
of PUFA may be slower, PUFA-rich TAG may donate
specific acyl groups to monogalactosyl diacylglycerol
(MGDG) and other polar lipids to enable rapid adaptive
membrane reorganization (Makewicz et al., 1997).