Continuous degradation of ciprofloxacin in a manganese redox cycling system driven by Pseudomonas putida MnB-1

Ciprofloxacin (CIP), as an extensively used antibiotic, has been widely detected at a high level in the environment and has raised environmental pollution concerns. Thus, efficient and cost-effective methods for CIP degradation are highly desired. Biologically produced manganese oxides (BioMnO(x)) offer a promising perspective for CIP degradation because of their catalytic reactivity and cost-effectiveness. However, the release of Mn(II) from BioMnO(x) prevents the further oxidation of pollutants. As a consequence, continuous CIP degradation by BioMnO(x) is not feasible. In this work, a manganese redox cycling system driven by Pseudomonas putida MnB-1 was constructed for continuous degradation of CIP. In such a system CIP was oxidized continuously and rapidly by re-oxidizing the formed Mn(II) to regenerate reactive BioMnO(x), which also protected the strain from CIP toxicity. CIP was degraded through N-dealkylation passway. No significant loss of BioMnO(x )reactivity was observed in three-cycle CIP degradation process, suggesting the stability of this system. An overlooked intracellular BioMnO(x), which was involved in CIP degradation, was discovered in P. putida MnB-1. Moreover, the important role of Mn(III) in facilitating CIP removal in this system was also identified. This work provides useful information to better understand the degradation of antibiotic compounds mediated by microbes in environments.(C) 2018 Elsevier Ltd. All rights reserved.