The present study examined the effect of heavy
metals (Mn2+ and Co2+) and hydrogen peroxide (H2O2) on
biomass, lipid content and lipid productivity of Chlorella
vulgaris. Manganese chloride at 2 μM, 10 μM and 12 μM
increased the lipid content significantly by 14 %, 16 % and
15 %, respectively, above the corresponding controls after
8 days of incubation, resulting in a significant (18 %) increase
in lipid productivity with respect to the control at 12 μM
manganese chloride. All applied concentrations of cobalt nitrate
increased the lipid content up to 25 % more than the
corresponding controls. The optimum concentration of cobalt
nitrate for high lipid productivity was 2.5 μM, which resulted
in a 22 % increase in lipid productivity over the control.
Furthermore, lipid productivity was increased significantly
by 29 % over the control when 4 mM hydrogen peroxide
was included in the culture medium. Additionally, the proportion
of total saturated fatty acids extracted from Chlorella
vulgaris treated with 12 μM manganese chloride, 2.5 μM
cobalt nitrate and 4 mM hydrogen peroxide ranged between
40 % and 45 % of total fatty acids. The present study concluded
that heavy metals and oxidative stress efficiently
increased the lipid productivity of the promising biodiesel
feedstock chlorophyte Chlorella vulgaris. In addition, the type
and proportion of individual fatty acids meet the biodiesel
standards. |
