Effect of CO2 aeration on cultivation of microalgae in luminescent photobioreactors

Abstract

This photobioreactor study investigated the influence of CO2 aeration on biomass production, carbon dioxide fixation rate, pH, cell’s essential elements such as carbon, nitrogen, and hydrogen, as well as lipid content, whilst under a range of luminescence-modified lighting conditions. The effect of aeration with pure air (comprising 0.03% CO2) on the CO2 fixation rate was insignificant compared to the higher concentrations used. Results showed that, with the exception of blue PBR, increasing CO2 concentrations in the air stream enhanced the fixation rate of CO2 in C. vulgaris. Cyanobacteria cells showed significant tolerance to 15% CO2.The results obtained demonstrated that the combination of blue light and 15% CO2 provided a condition in which higher rates of lipid accumulation was induced in both algal strains. The highest lipid content observed at this condition was 36.6% obtained in G. membrancea. Aeration with 15% CO2 enhanced lipid production of G. membranacea, to at least twice the amount produced at 5% CO2 in all photobioreactors. The most significant difference between the 5% and 15% CO2 aeration conditions was observed in the yellow PBR, in which the lipid content was enhanced up to six times.