BACKGROUND: Microbial electrosynthesis represents a promising approach for renewable energy storage in which chemically stable compounds are produced using CO2 as feedstock. This report describes the continuous production of acetate through microbial electrosynthesis from CO2 and assesses how the production rates could be increased. RESULTS: A continuous acetate production rate of 0.98mmol C LNCC-1 d-1 was obtained using CO2 as feedstock and with pH control around 5.8. These conditions increased substrate availability and favoured microbial electrosynthesis. Cyclic voltammograms demonstrated the electroautotrophic activity on the biocathode surface, which increased with pH control and caused current demand and acetate production rate to rise exponentially. CONCLUSION: pH decrease was shown to be an effective strategy to increase substrate availability and enhance microbial electrosynthesis. By making microbial electrosynthesis a feasible technology, CO2 could become an alternative feedstock for the carboxylate platform.