Maximize microalgal carbon dioxide utilization and lipid productivity by using toxic flue gas compounds as nutrient source

NOx and SOx present in flue gas inhibit microalgal based CO2 mitigation process. In this work, 13 microalgal strains were screened to evaluate their gradual acclimation capacity to toxic flue gas compounds, by testing their growth capability and photosynthetic ability in dissolved flue gas compounds. Six strains out of them were evaluated for their acclimation to bicarbonate and 15% CO2 as sole carbon sources. Two strains, Micractinium pusillum KMC8 and Scenedesmus acutus NCIM5584 were found to accumulate nitrite as fixed nitrogen and showed improved growth performance in photobioreactor upon stepwise acclimation to bisulphite/sulphite. Notably, the strain KMC8 showed a high tolerance and rapidly acclimated dissolved flue gas compounds with higher biomass yield (1.32 g L-1) and neutral lipid accumulation (32%), enhanced CO2 utilization efficiency (3.07%) and CO2 fixation rate (136.79 mg L-1 d(-1)) post acclimation. KMC8 sustained its stability in biomass and lipid productivity while simultaneously bio-mitigated CO2 under semi-continuous mode.