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

Abstract

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.