Time-dependent metabolic reprogramming in Scenedesmus sp. induced by intermittently sparged CO₂ concentrations

The increasing atmospheric CO₂ concentration resulting from anthropogenic emissions has been a major contributor to today's climate change. Microalgae have emerged as an integrated biological route for CO₂ capture and utilization; however, the altered metabolic fingerprints of indigenous microalgae to varying CO₂ concentrations remain underexplored. This study examines the physiological, biochemical, and metabolic fingerprint of the indigenous microalga Scenedesmus sp. under intermittently sparged varying CO₂ concentrations (5%, 10%, and 15%) with the aim of integrating microalgae into the circular economy. The results showed that varying CO₂ concentrations altered the physiological and metabolic responses of microalgae, thereby affecting carbon fixation, energy storage, and metabolite abundance related to growth and stress. Untargeted metabolomics identified 81 metabolites and revealed distinct metabolic signatures under varying CO₂ levels. Compared to 0.04% CO₂, 13 metabolites, including α-tocopherol and β-hydroxybutyric acid, were significantly upregulated (p < 0.05) under 5% CO₂ at late-log and stationary phase. At 10% CO₂, growth-associated metabolites (8), whereas at 15% CO₂, stress-responsive metabolites (8) were significantly upregulated. Overall, the dynamic metabolome signature laid the foundation for carbon partitioning in native Scenedesmus sp., highlighting CO₂ concentration-dependent metabolomics that can be utilized for integrated CO₂ fixation and metabolite production in circular biorefinery setup.