Heterotrophic precultivation is a better strategy than polarity reversal for the startup of acetate microbial electrosynthesis reactor

Microbial electrosynthesis (MES) is a novel technology which can capture CO2 to produce acetate. However, the difficulties on biocathode startup restricts the development of MES for acetate production. For exploring an efficient startup strategy, two strategies, i.e. heterotrophic precultivation (HP) and polarity reversal (PR), for the startup of acetate production MES were investigated in this study. After 9 cycles operation, the acetate production of HP was 79% higher than that of PR. Higher abundances of 16 S rRNA gene and fhs gene on the biocathode of HP than that of PR were revealed. Functional prediction indicated that HP had higher capacities of electron transfer and energy metabolism, and lower capacities of other pathways for acetyl-CoA competition. Though the biocathodes of HP and PR had relatively similar electrochemical characteristics, the advantages in the electrode microorganism abundance, microbial community structure and functions, resulted in the better acetate production performance of HP than PR. The study revealed that heterotrophic precultivation rather than polarity reversal is a better startup strategy of acetate microbial electrosynthesis reactor.