3.4. Enhancement of EPA and fucoxanthin production in P.
tricornutum.
Total EPA and fucoxanthin content is represented in Figure 2A &
B. The EPA content increased from 9 mg L-1 to 27 mg
L-1 in M4 condition within 10 days (Table 3) ,
which accounts for a ~3-fold increase compared to P1
control and ~ 2-fold increase in compare to M3
conditions. Content wise on 6th day, EPA was higher in
initial log phase accounting to 37 mg g-1 in the M2
condition, whereas M1 and M3 condition showed 34 mg
g-1 of EPA (Figure 2A) . Furthermore, EPA
content was higher in culture supplemented with only urea (P3) when
compared to NaNO3 (P1) on 4th and
6th day (Figure 2A) . Increase in EPA content
in the initial growth phase was reported earlier in the presence of urea[28] and glycerol
along with urea in P. tricornutum[29,
30,
56].
Along with EPA, fucoxanthin content was measured in various culture
conditions as depicted in Figure 2B. Higher fucoxanthin
production was observed in M4 conditions i.e., 11 mg
L-1 on 10th day of experiment
(Table 3) . This showed a ~ 4-fold increase in
fucoxanthin productivity compared to P1 and M3 conditions. Fucoxanthin
production was 6.62 mg L-1 in medium supplemented with
P2 on 10th day, whereas highest content was 21.9 mg
g-1 on 6th day of cultivation in the
P1 condition (Figure 2B) . Addition of glycerol limited the
nitrogen content in the medium, and thus a decrease in the fucoxanthin
content is observed in glycerol supplementation (M1 and M3)
(Figure 2B) , although higher production is observed in M2
condition compared to M1 and M3 conditions, which can be justified by
the presence of two nitrogen source and residual N in the medium until
10th day (Figure S1, S2, S3, Supporting
information) . Fucoxanthin being a primary carotenoid is highly
influenced by nitrogen content in the medium[57]. Previous
reports highlights higher fucoxanthin content in P.tricornutumcultivated in nitrate-enriched medium[7,
16], thus feeding cultures with urea,
increased biomass and the biomass associated metabolites i.e. EPA and
fucoxanthin.