Continuous long-term bioelectrochemical chain elongation to butyrate

We demonstrate here the long-term continuous bioelectrochemical chain elongation from CO2 and acetate by using a mixed microbial culture. The role of applied current (3.1 vs. 9.3 A m−2) on the performance was investigated. The main product was n-butyrate which was continuously produced over time. Trace amounts of propionate and n-caproate were also produced, but no alcohols were detected during the whole course of the experiment (163 days). Microbial electrosynthesis (MES) systems controlled with more current (9.3 Am−2) showed a butyrate concentration that was 4.5 times higher (maximum 0.59 g L−1) and increased volumetric production rates (0.54 g L−1 day−1) compared to the low-current reactors (0.12 g L−1 day−1), at 58.9 and 71.6 % electron recovery, respectively. Biocatalytic activity of the microbial consortia was demonstrated. This study revealed that the solid-state electrode does control the chain elongation reaction as an essential electron donor and determines the performance of MES systems. This study highlights MES as a promising alternative for acetate upgrading