Maximizing CO2 biofixation of Arthrospira platensis using an in situ bicarbonate pool: Optimization of CO2-regulated pH and bicarbonate concentration

The highly alkaline environment required for Arthrospira cultivation has great potential for CO₂ capture and utilization, but less attention has been paid. Here, we used Arthrospira medium as an in situ carbon pool to improve biomass production, carbon fixation, and capture efficiencies. Under optimized pH 8.5–10.5 and 8.4 g L⁻¹ sodium bicarbonate, the highest carbon fixation rates of Arthrospira platensis reached 295.68–304.75 mg L⁻¹ d⁻¹ and 26.35 g m⁻² d⁻¹ in a 3-L reactor and 5 m² runway pond, respectively, and produced biomass with abundant of phycocyanin and carotenoids. Furthermore, carbon fixation rates of 24.73–26.93 g m⁻² d⁻¹ and exogenous CO₂ utilization efficiencies of 72.62–78.24 % were obtained by culture in a large-scale 200-m² runway pond. Overall, this study established an in situ carbon pool system suitable for Arthrospira for carbon capture and fixation, which effectively promotes the use of Arthrospira in carbon emission reduction.