Effects of resazurin on perchlorate reduction and bioelectricity generation in microbial fuel cells and its catalysing mechanism

•Resazurin was used as a redox mediator in MFCs with perchlorate wastewater.•The perchlorate reduction rates and output voltage were enhanced by resazurin.•The analysis of EPS was used in MFCs with perchlorate wastewater.•The respiratory chain of the MFCs was determined by respiratory inhibitors.•The role of resazurin in MFCs was studied by respiratory inhibitors.

Resazurin could improve the performance of microbial fuel cells (MFCs). Compared with a mediator-free MFC, MFCs with 3 μM resazurin, 6 μM resazurin, and 9 μM resazurin exhibited increases in perchlorate reduction ratio of 50.8%, 72.6% and 101.6%, respectively, and increases in the output voltage of 24.5%, 33.3% and 41.7%, respectively. An electrochemical analysis indicated that adding resazurin decreased the anode resistance and enhanced the biocatalytic activities of the anode. The content of humic acid increased, and the content of polysaccharide decreased in the resazurin-addition MFCs, which accelerated the transfer of electrons to the anode. Adding 9 μM resazurin to MFC with one of eight different inhibitors (6 μM) demonstrated that the acceleration sites of resazurin were NADH-ubiquinone reductase, NADH reductase and methylnaphthoquinone. A microbial analysis showed that adding resazurin changed the composition of the anodic microbial community and stimulated the growth of certain dominant species.