A CO2‑rich environment‑mediated amelioration of nutritional stress effect in an indigenous freshwater green microalga Desmodesmus sp.

Microalgae from natural habitats have the potential for biomitigation of atmospheric CO 2 . The nutritional stress induces
the microalgae to accumulate metabolites like lipids and carotenoids but limits the growth and biomass yield. The present
study focused on the growth, productivity, lipid, chlorophyll, and carotenoid contents of an indigenous fresh water microalga
Desmodesmus sp. subjected to nutritional (nitrogen and salinity) stress under a CO 2 -rich environment (20% CO 2 ). The 20%
CO 2 supplemented stressed cultures showed a final biomass concentration of 0.28-0.38 g L -1 , productivity of 0.01-0.02 g
L -1 day-1 , specific growth rate (μ max day –1 ) of 0.09-0.11, and CO 2 biofixation rate ( RCO2 ) of 0.024-0.04 g L -1 day-1 which was
1.5-2.25 fold, 2-3.63 fold, 1.57-2.25 fold and 2.3-4.3 fold higher, respectively than their corresponding cultures supplemented
with ambient level of CO 2 . The chlorophyll, carotenoid, and lipid content of stressed cultures supplemented with 20% CO 2
was 1.3-2.2 fold, 3-5 fold and 1.4-2.1 fold higher than the corresponding cultures supplemented with ambient level of CO 2 .
The relative percentage of oleic acid total fatty acid of stressed cultures supplemented with 20% CO 2 was in the range of
48-58%, i.e., 1.11 to 1.45 fold higher than the corresponding cultures supplemented with ambient level of CO 2 . Thus, the
supplementation with elevated levels of CO 2 ameliorated the effect of nutritional stress in the microalga enabling the accu-
mulation of high content of metabolites with an increase in biomass.