Simultaneous microbial electrosynthesis of acetate and butyrate from carbon dioxide in bioelectrochemical systems

Bioelectrochemical systems(BESs) can be used for microbial electrosynthesis, producing organic chemicals from carbon dioxide by recovering energy from the wastewater in situ. By constructing a bioelectrochemical system, this study focused primarily on reduction of carbon dioxide to acetate and butyrate by mixed cultures as electrocatalytic agents. At a set cathode potential of-0.75 V(vs Ag/AgCl) in the build-up bioelectrochemical system, the maximum concentration of acetate was 251.89 mg/L in 10 days of a reaction cycle. Butyrate appeared on the third day of the reaction, and the maximum concentration of butyrate was 89.42 mg/L. The total electron recovery of BESs reached 85.04%. The electrochemical analysis of the biocathode showed its excellent catalytic activity. PCR-DGGE of biocathode suggested the main microbial populations were Acetobacterium and Bacteriodes. This research proved that biocathode has the ability to produce acetate with carbon dioxide as the original substrate, and to further elongate medium chain fatty acids.