Medium chain fatty acid production from CO2 in integrated dark fermentation-microbial electrosynthesis reactor.

Emerging technologies aim to convert CO2 into biofuels and chemicals, reducing greenhouse gas emissions. Microbial electrosynthesis (MES) offers promise for producing organic products, but challenges remain in energy efficiency and medium-chain fatty acid (MCFA) synthesis. This study demonstrates long-term, continuous caproic acid production in an integrated dark fermentation-MES (DF-MES) system using enriched mixed cultures. A maximum caproic acid production rate of 0.47 ± 0.16 g L-1 d-1 was achieved, with a 73 % selectivity, 83 % carbon recovery and 94 % electron recovery. Integration of DF reduced external energy demand by 60 %, while continuous operation increased production rates by 14.6 % over batch mode, maintained stability for over three months. These findings highlight DF-MES integration as a viable approach to reducing energy demand while ensuring sustained caproic acid production.