Profiling of co-metabolic degradation of tetracycline by the bio-cathode in microbial fuel cells

Abstract

In this paper, a system of tetracycline (TEC) degradation by the bio-cathode in a microbial fuel cell (MFC) was constructed. Overall, the co-metabolic degradation performance of TEC was studied through single factor experiments and the ecological risk was evaluated using the <i>E. coli</i> growth inhibition rate and resistance genes. High throughput sequencing (HTS) was utilized to profile the biofilm community structure of the bio-cathode. Results showed that the degradation rate of TEC reached greater than 90% under optimal conditions, which was 10 mg L^-1 initial TEC concentration, 0.2-0.7 g L^-1 sodium acetate concentration and 12-18 L h^-1 aeration. Furthermore, compared with the aerobic biodegradation of TEC, the degradation efficiency of the MFC bio-cathode for TEC was significantly increased by 50% and the eco-toxicity of TEC after 36 hour degradation was reduced by 60.9%, and TEC ARGs in effluent were cut down. HTS results showed that electrochemically active bacteria <i>Acetobacter</i> and TEC-resistant degradation bacteria <i>Hyphomicrobium</i>, <i>Clostridium</i> and <i>Rhodopseudomonas</i> were the main dominant bacteria in the cathode biofilm. Besides, based on 5 intermediates, degradation pathways involving deamidation, denitro dimethylation, dedimethylation and dehydroxylation of TEC were proposed. The degradation of TEC on the bio-cathode was mainly caused by microbial co-metabolism action. This study would enrich the study of MFC bio-cathodic degradation of antibiotics in water.