Study on the selective regulation of microbial community structure in microbial fuel cells by magnetic field-coupled magnetic carbon dots.

Microbial fuel cells (MFCs), as a green energy technology that simultaneously enables electricity generation and wastewater treatment, exhibit performance that is highly dependent on the structural distribution of the microbial community. In this study, we investigated the effect of magnetic field (MF)-coupled magnetic carbon dots (N-CD/FeO) as a selective pressure on the structure of mixed microbial communities in an intermittent pulsating fluidized-bed bioelectrochemical reactor. Under a moderate magnetic field (15 mT), N-CD/FeO were effectively adsorbed onto microbial cells and subsequently aggregated, significantly enhancing electron transfer within the community. The maximum power density reached 38.43 mW/m, which is about 5.07 times that of the blank control group. 16S rRNA and metagenomic analyses showed that the MF (15 mT) group exhibited significant enrichment of typical electroactive bacteria (40.32 %), such as Geobacter, which directly contributed to improved power production performance. In contrast, under a stronger magnetic field (60 mT), the abundance of typical electroactive bacteria (17.94 %) decreased, while atypical electroactive (38 %) and metabolically complementary bacteria that facilitate syntrophic cooperation (42.85 %) showed adjusted abundances, forming a functionally more balanced microbial community with improved adaptability to real wastewater conditions. This study demonstrates that by tuning magnetic field intensity and coupling with magnetic carbon dots, the structure and function of microbial communities can be directionally regulated, providing an effective strategy for developing electroactive inocula with enhanced power generation and wastewater adaptability.