Reducing CO₂ emissions is one of the most pressing challenges of our time in mitigating the impacts of climate change. The microbial utilization of CO₂-containing syngas, which is produced as by-product in many industrial processes, offers an ecologically sustainable solution for producing materials without the use of fossil fuels.

Acetogenic microorganisms, such as Clostridium carboxidivorans, can convert syngas into organic acids and alcohols, but only small amounts of longer-chain acids and alcohols is produced, which are economically of more interest. To generate longer-chain fermentation products, the anaerobic bacterium Clostridium kluyveri can be used, which can produce butyrate, hexanoate, and small amounts of octanoate from ethanol and acetate (chain elongation). In co-cultivations of these two microorganisms with CO-containing syngas, we have already shown that the organic acids produced during chain elongation can also be reduced by the syngas converting Clostridium carboxidivorans to their corresponding alcohols.

However, high CO partial pressures, which are necessary for acetogenic microorganisms, have proven to be critical, as even small amounts of CO inhibit the growth of Clostridium kluyveri. This research project addresses this issue: using adaptive laboratory evolution (ALE), we aim to generate Clostridium kluyveri strains that can grow even at high CO partial pressures. The genetic changes thus obtained will be identified through genome sequencing and transferred back to the original strain via reverse engineering by our project partner. The new Clostridium kluyveri strains will then be used in syngas fermentation processes in synthetic co-culture with Clostridium carboxidivorans to efficiently produce high concentrations of long-chain alcohols from syngas.