Bio-capture and influence of CO2 on the growth rate and biomass composition of the microalgae Botryococcus braunii and Scenedesmus sp

•Anthropogenic activities are the major cause of increased CO2 concentration in the atmosphere.•Influence of CO2 on the growth rate and biomass composition of microalgae is investigated.•The carbon fixation ability of Botryococcus braunii and Scenedesmus sp. was evaluated.•Microalgae could be an excellent alternative to forced CO2 capture. Currently, there is an increase in CO2 concentration in the atmosphere due to the many anthropogenic activities. This increase comes along with global consequences on an environmental, social, and economic scale. Due to these consequences, there is an interest in developing alternatives for CO2 capture, including microorganisms, for this purpose. The present study researches the microalgal strains Botryococcus braunii and Scenedesmus sp. to capture CO2 and the production of carbohydrates, proteins, and lipids, with 0.03 % (CO2 concentration in air), 10 %, and 20 % CO2 supply. It was found that B. braunii growth was affected by the highest CO2 concentration since the results showed biomass production 0.64 g L−1, 0.41 g L−1, and 0.26 g L−1 with air, 10 %, and 20 % CO2, respectively. On the other hand, Scenedesmus sp. showed an increase in biomass, carbohydrates, and protein production as the CO2 concentration increased, reaching the highest values of 1.95 g L−1, 422.72 mg L−1, and 259.39 mg L-1 at 20 % CO2, respectively. Additionally, the CO2 removal efficiency was highest in the culture of B. braunii and Scenedesmus sp. at 10 % CO2, reaching a value of 6.78 % and 6.60 %, respectively. This study shows that each microalga strain is directly affected by biomass growth and biomass composition depending on the strain. Furthermore, our study showed that microalgae could be an excellent alternative to forced CO2 capture, where the CO2 from flue gas can be driven from an industrial chimney to the photo-bioreactors.