Methanol as a co-substrate in the microbial electrosynthesis

Methanol is a promising feedstock for the bio-based economy as it can be derived from organic waste streams or produced electrochemically from CO2 and thus, avoid competition with food production compared to ethanol. Methanol can be utilized by microorganisms as the carbon and energy source for the production of valuable platform chemicals. Acetate production from CO2 in microbial electrosynthesis (MES) has been widely studied, although more valuable compounds such as butyrate are currently attracting attention. Here we show that methanol can be used as a co-substrate with CO2 and enhance butyrate production in MES. Feeding with CO2 and methanol resulted in the highest butyrate production rates and titers of 0.4 ± 0.0 g L-1 d-1 and 8.6 ± 0.2 g L-1, respectively, outperforming reactors with only CO2 feeding (butyrate production rates and titers of 0.2 ± 0.0 g L-1d-1 and 5.2 ± 0.1 g L-1, respectively). Methanol acted as an electron donor and as a carbon source (methanol and CO2 contributed ca. 50% of the carbons to the products). A specific microbiome with Eubacterium as the dominant genus was responsible for the butyrate production from CO2 and methanol in MES. The results demonstrate an attractive route for the use of the low-cost C1 substrates i.e. CO2 and methanol, to improve the MES performance by achieving butyrate as the main product. Abstract text goes here. The abstract should be a single paragraph that summarises the content of the article