Mechanism of Fe/Mn-MOFs accelerating electron transfer to promote bisphenol A biodegradation by Proteus mirabilis

Electron transfer efficiency is closely related to the efficiency of bacterial Bisphenol A (BPA) degradation. However, few studies have revealed the mechanisms by which exogenous nanomaterials promote bacterial degradation ability from the perspective of electron transfer. In this study, Fe/Mn bimetallic metal-organic frameworks (Fe/Mn-MOFs) prepared in our previous work and the BPA-degrading strain SQ-2 were used as research materials. Fe/Mn‑MOFs promoted the degradation of 10 mg/L BPA by SQ‑2 under both aerobic and anaerobic conditions, with promotion rates of 98% and 75%, respectively. Further investigation revealed that inhibited ubiquinone activity was the limiting factor in the electron transfer chain of SQ‑2 under aerobic conditions, and Fe/Mn‑MOFs significantly alleviated this inhibition, achieving a relief rate to 148.94%. Integrated morphological, electrochemical, and proteomic analyses indicated that, regardless of whether ubiquinone was inhibited, Fe/Mn‑MOFs could enhance electron generation and also acted as electron shuttles to enhance bacterial electron transfer activity. Under normal conditions (ubiquinone not inhibited), Fe/Mn‑MOFs strengthened the electron transfer efficiency by upregulating NADH dehydrogenase, cyt-c oxidase, and riboflavin production, thus accelerating degradation. When ubiquinone was inhibited, Fe/Mn‑MOFs stimulated upregulation of NADH dehydrogenase and replenished quinone species to alleviate electron transfer chain inhibition. Besides, it constructed an alternative electron transfer pathway independent of ubiquinone to restore electron flow. Concurrently, Fe/Mn-MOFs enhanced stress resistance abilities, ultimately restoring the degradation performance. Fe/Mn-MOFs function not only as electron transfer enhancers under normal conditions but may also as bypass reconstructors capable of sustaining BPA degradation when ubiquinone function was impaired. Results provide a new research reference for using exogenous materials to enhance the bacterial degradation of BPA.