Bubble column photobioreactor (BCPR) for cultivating microalgae and microalgal consortium (Co-CC) with additional CO2 supply for enhancing biomass, lipid, and preferable fatty acids production

The present study has designed and developed a 5 L bubble column photobioreactor (BCPR) to investigate two
microalgal strains Chlorella sp. S-01, Chlorella sp. S-02 and their consortium Co-CC (Chlorella sp. S-01 + Chlorella
sp. S-02) at 0.03, 5, and 10% CO2 supply for biomass and lipid production. The dry cell weight of Chlorella sp. S-
01, Chlorella sp. S-02 and Co-CC were, respectively about 1.41, 1.32, and 1.39 g/L on the 20th day without CO2
supply, while it was 1.76, 1.61, and 1.87 g/L, respectively at 10% CO2 supply and similarly, chlorophyll-a
content was higher in 10% CO2 supplied condition over control. Interestingly, Co-CC grown at all the CO2
concentrations showed similar lipid content between 19.30 and 1F9.41%. As an integrated refinery approach, deoiled
biomass of Co-CC was subjected to carbohydrates and protein estimation and found that 46.2% and 30.80%
in 10% CO2 supply condition in BCPR. Lipid extracted from the Co-CC grown under 0.03, 5, and 10% CO2 supply
in 5L BCPR was converted to biodiesel, and the biodiesel yield was estimated to be 62.78%. Further, the fatty
acid profile of Co-CC grown at 10% CO2 showed higher levels of C16:0, C16:1, C18:1, and monounsaturated fatty
acids contents over other CO2 supplied conditions. Biodiesel of Co-CC showed favourable fuel properties such as
density, higher heating value, oxidative stability, CFPP, viscosity, degree of unsaturation, saponification value,
and cetane number, which were also in accordance with ASTM, and EN, biodiesel standards.