Continuous Long‐Term Bioelectrochemical Chain Elongation to Butyrate

Abstract

Abstract We demonstrate here the long‐term continuous bioelectrochemical chain elongation from CO 2 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.