Enhancement of fipronil degradation with eliminating its toxicity in a microbial fuel cell and the catabolic versatility of anodic biofilm

The degradation of fipronil was investigated in microbial fuel cells (MFCs). Almost 79% of 30 mg/L fipronil was rapidly degraded within 12 h by MFC biofilm. Based on the constructed quadratic polynomial model, a maximum fipronil degradation rate of 94.22% could be theoretically achieved at pH of 7.01, 33.39 degrees C, and the initial fipronil concentration 74 mg/L after incubation for 72 h. The high acute toxicity of fipronil toward zebrafish was largely eliminated after degradation by the MFC. In addition, the MFC biofilm showed catabolic versatility to 4-chloronitrobenzene, sulfanilamide, fluoroglycofen, and azoxystrobin. The microbial community analysis revealed that the functional bacteria Sphaerochaeta, Pseudomonas, Azospirillum, Azoarcus, and Chryseobacterium were major predominant bacteria in the anodic biofilm. Therefore, the MFC offers a promising approach in treating the environmental contaminants due to its abilities of energy capture from waste substances and catabolic versatility to different organic compounds.