Degradation efficiency of antibiotics by the sewage-fed microbial fuel cells depends on gram-staining property of exoelectrogens

Microbial fuel cells (MFCs) are green technologies for bioenergy capture. Gram-negative bacteria have been shown as the dominant electrogenic functional microbes on the anode of MFC. However, how gram-positive bacteria perform in the mixed colonies remains unclear. In this study, specific classes of antibiotics are employed to characterize the properties of electroactive microorganisms in the sewage-fed MFC. Our results reveal that MFCs exhibit high efficiencies in degrading some widely used bacterial antibiotics and generating electricity, while being significantly influenced by gram-staining properties of microbial communities. The MFC is effective against the broad-spectrum bacterial antibiotic cefepime with a degradation efficiency of 92.5% (5 mg/L) and a maximum power density of 263.6 mW/cm2 (25 mg/L). Electrochemical analyses demonstrate that the gram-positive bacteria on anode are more resistant to their specific antibiotic vancomycin and the maximum power output of the system is enhanced by 13.7%. Furthermore, the exoelectrogens in the mixed colonies show insensitivity to fungi-specific antibiotics such as amphotericin with extremely low degradation rate (<4.5%). Our findings provide a new perspective on exploring the characteristics of functional exoelectrogens based on the microbial responses to antibiotics with specific antibacterial spectrum. It is also crucial to guide the application of bioelectrochemical systems in medical wastewater treatment for urban sustainable development.