Improvement carbon monoxide tolerance and production of 2, 3-BDO in Eubacterium limosum by adaptive laboratory evolution. undefined

Acetogenic bacteria (acetogen) are microorganisms with high potential as biocatalysts that can convert C1 gas, such as CO2 or CO, into biomass or biochemicals, but high concentrations of CO gas cause growth retardation in these microorganisms. In this study, we performed adaptive evolution of Eubacterium limosum, one of the acetogen, for about 400 generations under high CO syngas conditions to obtain E. limosum ECO2, which can rapidly proliferate even under high CO conditions. It was revealed that there was a mutation in H636R in the ACS protein of the ECO2 strain through whole-genome re-sequencing, and it was proved that the mutation increased the CO gas conversion rate. In addition, by analyzing the transcript profiling of the ECO2 strain under high CO syngas conditions, the transcript level of methyl-branch in the wood-ljungdahl pathway and the energy conservation system were increased under high-concentration CO gas conditions. Finally, to develop CO to value-added biochemicals, 2,3-BDO biosynthesis pathways were constructed and transformed to the E. limosum ECO2 strain. This strain can produce 2.60 mgL-1h-1 of 2,3-BDO through CO 66% syngas fed-batch fermentation. It is 4.5 fold higher than the wild type. Therefore, we develop high CO tolerance microorganism, and this strain have a high application potential as a biocatalyst that can efficiently convert CO gas into value-added chemicals.