Efficient anaerobic biodegradation of trimethoprim driven by electrogenic respiration: Optimizing bioelectro-characterization and mechanisms

In this study, a bioelectrochemical system, with trimethoprim (TMP) as the sole carbon source, was constructed to evaluate the bioelectrogenic respiration on the acceleration of TMP degradation. The bioelectro-characterization was comprehensively optimized. The bioelectrogenic role of microbial anode in the degradation of TMP were assessed by the degradation performance, degradation pathways, anode functional microbial communities, and antibiotic resistant genes (ARGs) accumulation. The results showed that the optimal removal efficiency of TMP was achieved (98.21%) when the external resistance, pH, and concentration of phosphate buffer solution (PBS) were 1000 ohm, 7, and 25 mM, respectively. The potential degradation pathways of TMP were speculated based on Liquid Chromatography-Mass Spectrometry (LC-MS) and density functional theory (DFT) calculations, including hydroxylation, demethylation, demethylation, and methylene bridge cracking. Electroactive bacteria and potential degraders were significantly enriched in the bioelectrogenic anaerobic treatment system, where bioelectrogenic respiration played a crucial role in promoting TMP biodegradation. However, it was observed that under long-term toxic stress of TMP, there was an enrichment of ARGs among the TMP-degrading bacteria. Furthermore, the comprehensive interaction between microbial communities and environmental variables was extensively investigated, revealing a strong positive correlation between electroactive bacteria and potential degraders with TMP removal and biomineralization efficiency. This study provided guidance and promising strategy for the effective treatment of antibiotic-containing wastewater in practical applications.