Selective enrichment of homoacetogens and optimization of the operational conditions for effective acetate production in hydrogen-mediated microbial electrosynthesis reactors

Microbial electrosynthesis (MES) can use microorganisms and power to convert CO₂ reduction into valuable chemicals. The non-biofilm-driven and H₂-mediated MES could dramatically enhance the current density of MES reactors. However, thus far there is no enriched microbial community dedicated to H₂-mediated MES for acetate production. Here, we enriched a highly efficient hydrogenotrophic acetate-producing microbial consortium (Acetobacterium abundance 85%) from anaerobic granular sludge in an H₂-mediated MES reactor. Then, orthogonal experiments were used to optimize the operational conditions for this enriched consortium. The optimal operational conditions were 37 °C, pH 7.5, and 400 rpm. The maximum acetate production rate (1.77 g/L/d) and acetate titer (24.6 g/L) obtained under the optimal conditions were higher than most reported MES reactors. This study demonstrated that selective enrichment of the hydrogenotrophic acetate-producing microbial community and optimization of the operational conditions could effectively enhance the performance of H₂-mediated MES reactors.