Degradation of enrofloxacin with natural manganese oxides and enhancement by manganese oxidizing bacteria

Natural manganese oxides (n-MnOx) widely exist in the nature and may contribute to the elimination of organic contaminants. The present study investigated the degradation of frequently detected fluoroquinolone antibiotic enrofloxacin (EFX) and the degradation kinetics were analyzed. During the reaction, the valence of Mn in n-MnOx changed with the release of Mn ions. It was also found that combing manganese oxidizing bacteria with n-MnOx can enhance the degradation of EFX and alter the degradation pathway as well. The transformation products of EFX were analyzed with UPLC-MS/MS, which revealed seven products. Based on them, it is proposed that the degradation may start with the dehydrogenation from the piperazine moiety that was further broken down. Respirometry tests demonstrated that the degradation with n-MnOx significantly reduced the toxicity of EFX. This study proved the oxidation with n-MnOx as a simple and effective technology to remediate the contamination of enrofloxacin and other fluoroquinolones and the potential of combing the special capacity of microorganisms.