In Situ Quorum Quenching Effect Induced by Negative Potential on Electro-Conductive Membranes for Membrane Fouling Control in Membrane Bioreactors

Membrane fouling is a major impediment to the widespread application of membrane bioreactors (MBRs) for water treatment. In recent years, the electro-conductive membrane bioreactor (E-MBR) has demonstrated efficacy in mitigating membrane fouling. The application of a negative potential to the electro-conductive membrane promotes electrostatic repulsion, effectively displacing negatively charged extracellular polymeric substances (EPS) away from the membrane surface. However, given the established vital role of quorum sensing (QS) in membrane fouling development, the interference of the negative potential on QS-mediated EPS secretion and biofilm formation has been largely overlooked. Herein, we found that the negative potential applied to the electro-conductive membrane could effectively suppress the QS process, thereby inducing the in situ quorum quenching (QQ) effect. The application of negative potential significantly reduced the levels of the signal molecule C14-HSL as well as EPS. Metagenomic analysis indicated that the relative abundance of the "signal transduction mechanism" pathway was suppressed, and the functional genes encoding C14-HSL receptor proteins belonging to "LuxR family" was downregulated in the cake layer of E-MBR. Density functional theory calculations and molecular dynamics simulation results revealed that the application of negative potential enhanced the electrostatic repulsion between the membrane and C14-HSL and induced the conformational changes of the LuxR protein, which synergistically induced the in situ QQ effect. This study provides a novel perspective on the antifouling mechanism in E-MBR.