Nitrogen-doped carbon dots boost microbial electrosynthesis via efficient extracellular electron uptake of acetogens.

ABSTRACT

This study investigated the molecular mechanism behind the highly efficient performance of nitrogen-doped carbon dots (NCDs)-assisted microbial electrosynthesis systems (MESs). The impact of NCDs (CN precursor = 10.5-13) on acetogens was examined in the biocathode. The highest electrocatalytic performance was observed with NCDs11. The maximum acetate production rate of 1.9 ± 0.1 mM d-1 was achieved in NCDs11-modified MESs, which was 26.7-216.7 % higher than other MESs (0.6-1.5 mM d-1). With NCDs11 modified, the biocathode exhibited a 129.3-186.8 % increase in the abundance of Sporomusa, and 38.5-104.6 % increase in cytochrome expression (cydAB, cybH). Transcriptome confirmed that cytochromes played a crucial role in the extracellular electron uptake (EEU) of NCDs11-modified Sporomusa. NCDs11 enhanced EEU efficiency, thereby increasing the two H+-pumping steps and accelerating microbial CO2 fixation. These results provide valuable insights into increasing CO2 fixation by maximizing EEU efficiency in acetogens.