C1Bio-Nano · Microbial Hybrid System Coupled with Biogenic FeS Nanoparticles for Efficient C1 Gas Conversion to Medium-Chain Carboxylic Acids

Carbon neutrality is a central objective of the European Union, requiring breakthrough solutions to lower industrial CO and CO2 emissions. Bioconversion of C1 gases into valuable chemicals provides such a sustainable pathway, combining emission reduction with circular bioeconomy benefits, while ensuring safety, no secondary pollution, and mild operating conditions. Acetogenic microbes such as Clostridium aceticum fix C1 gases via the Wood-Ljungdahl pathway (WLP), efficiently converting CO and CO2 into acetyl-CoA, which is further transformed into acetic acid and ethanol. These intermediates serve as precursors for medium-chain carboxylic acids (MCCAs), bio-based chemicals that can replace petroleum-derived products. However, slow electron transfer and metabolic bottlenecks limit ethanol production. To overcome this, the C1Bio-Nano project addresses this by integrating C. aceticum with FeS-coated Shewanella oneidensis MR-1 in continuous stirred-tank reactors, enhancing interspecies electron transfer, NADH regeneration, and ethanol synthesis. Building on this approach, it will (O1) optimize the MR-1@FeS NP–C. aceticum coculture to achieve ethanol/acetate ratio >2 and >30% efficiency gain; (O2) elucidate electron transfer and NADH mechanisms using isotopic labeling, electrochemical analysis, and 13C tracing during a secondment at Dr. Vogt's lab (UFZ, Germany); (O3) convert ethanol and acetate into MCCAs with Clostridium kluyveri, aiming for >30% yield improvement and enhanced carbon recovery via controlled CO2 loading and ethanol/acetate ratios, supported by kinetic-metabolic modeling. This project will develop a mild-condition, FeS NP-assisted microbial system for scalable, selective carbon fixation and MCCAs production, equipping the fellow with advanced skills in microbial electron syntrophy, fermentation engineering, and isotopic tracer analysis, while generating results relevant to EU industrial carbon valorization and sustainable chemical production.