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

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.