Embedding carbon quantum dots in cell envelops to accelerate electron transfer for microbial advanced oxidation

Microbial advanced oxidation, a crucial pathway for pollutant decomposition in the natural environment, is typically limited by microbial extracellular respiration. This is because the electro-inert cell walls of common microorganisms, such as Bacillus subtilis, hinder the cross-wall electron transfer necessary for reducing ferric species and inducing Fenton-like reactions. In this study, carbon quantum dots (CDs) were fed to promote the extracellular respiration of B. subtilis to strengthen the microbial advanced oxidation of aniline. The results showed that the CDs were embedded in the cell wall of bacterial cells to improve the extracellular electron transfer, which increased the •OH production (by 60.25%) and the aniline degradation. Meanwhile, the •OH generation mainly increased outside of the cell, which was beneficial for the degradation of pollutants and for relieving the damage of the radical to bacterial cells. The CDs induced the polarization of amide groups in the cell walls to maintain actively proton-coupled electron transfer to increase ATP generation by 39.28%. Feeding CDs provided a potential strategy to strengthen the extracellular respiration of common microorganisms and increase pollutant degradation via microbial advanced oxidation in the environment.