Harnessing CO₂ for sustainable bioelectricity: An engineered two-stage microbial co-culture approach with enhanced...

Climate change driven by rising atmospheric CO₂ levels underscores the urgent need for sustainable energy solutions. This study investigates the dual potential of CO₂ as a primary carbon source and acetate as an intermediate to simultaneously mitigate atmospheric CO₂ levels and generate bioelectricity using microbial fuel cells (MFCs). A synthetic microbial co-culture was developed, combining Clostridium ljungdahlii for CO₂ sequestration and Shewanella oneidensis MR-1 for bioelectricity production. To optimize MFC performance, S. oneidensis was modularly engineered to enhance acetate metabolism and electron transfer efficiency. Key modifications included upregulating ATP synthesis, introducing an ATP-independent acetate metabolic pathway, increasing NADH availability, and optimizing pili-based artificial conductive nanowires. These advancements achieved a maximum cell density (OD₆₀₀ = 0.611), a record output voltage of 351.3 mV, and a record power density of 94.9 mW/m² using acetate as the substrate. Furthermore, a two-stage biocatalytic system utilizing CO₂ as the primary carbon source yielded an output voltage of 209.3 mV and a power density of 65.0 mW/m². These results highlight the potential of engineered microbial co-culture for efficient CO₂-based bioelectricity generation, offering a scalable and sustainable pathway toward carbon-neutral energy production.