Highly selective butanol production by manipulating electron flow via cathodic electro-fermentation

Butanol production by solventogenic Clostridia shows great potential to combat the energy crisis, but is still challenged by low butanol selectivity and high downstream cost. In this study, a novel cathodic electro-fermentation (CEF) system mediated by methyl viologen (MV) was proposed and sequentially optimized to obtain highly selective butanol production. Under the optimal conditions (-0.60 V cathode potential, 0.50 mM MV, 30 g/L glucose), 7.17 +/- 0.55 g/L butanol production were achieved with the yield of 0.32 +/- 0.02 g/g. With the supplement of 4 g/L butyric acid as co-substrate, butanol production further improved to 13.14 +/- 1.14 g/L with butanol yield and selectivity as high as 0.43 +/- 0.01 g/g and 90.44 +/- 1.66%, respectively. The polarized electrode enabled the unbalanced fermentation towards butanol formation and MV further inhibited hydrogen production, both of which contributed to the high-level butanol production and selectivity. The MV-mediated CEF system is a promising approach for cost-effective bio-butanol production.

Automated summary

In this study, a novel cathodic electro-fermentation system mediated by methyl viologen was used to achieve selective and high-yield butanol production. The addition of butyric acid as a co-substrate further improved the production and selectivity of butanol. This approach holds great promise for cost-effective bio-butanol production.