Biotechnological potential of Chlorella sp. and Scenedesmus sp. microalgae to endure high CO₂ and methane...

Biogas, a gaseous effluent from the anaerobic digestion of organic waste, is considered an important source of energy, since it has a composition mainly of methane (CH₄; 55-75%) and CO₂ (20-60%). Today, CO₂ from biogas is an excellent carbon source to induce high microalgal biomass production; however, each microalga strain can have different optimal CO₂ concentrations for maximizing their bio-refinery capacity as well as different ability to endure stressful conditions of industrial effluents. This study assessed the bio-refinery capacity of Chlorella sp. and Scenedesmus sp., native of Lago de Chapala, Mexico, from biogas, as well as the effect of high CO₂ and methane concentrations on the physiological performance to grow, capture CO₂ and biochemical composition of both microalgae cultured under different biogas compositions. The results show that both microalgae have the biotechnological potential to endure biogas compositions of 25% CO₂-75% CH₄. Under this condition, the biomass production attained by Chlorella sp. and Scenedesmus sp. was 1.77 ± 0.32 and 2.25 ± 0.20 g L^-1, respectively, with a biochemical composition mainly of carbohydrates and proteins. Overall, this study demonstrates that both microalgae have the ability to endure the stressful biogas composition without affecting their physiological capacity to capture CO₂ and biosynthesize high-value metabolites. Moreover, it is worth highlighting the importance of screening wild-type microalgae from local ecosystems to determine their physiological capacity for each biotechnological application.