Biodegradation of ofloxacin, norfloxacin, and ciprofloxacin as single and mixed substrates by Labrys portucalensis F11

Abstract

Fluoroquinolone (FQ) antibiotics are extensively used both in human and veterinary medicine, and their accumulation in the environment is causing an increasing concern. In this study, the biodegradation of the three most worldwide used FQs, namely ofloxacin, norfloxacin, and ciprofloxacin, by the fluoroorganic-degrading strain Labrys portucalensis F11 was assessed. Degradation occurred when the FQs were supplied individually or as mixture in the culture medium, in the presence of an easily degradable carbon source. Consumption of individual FQs was achieved at different extents depending on its initial concentration, ranging from 0.8 to 30 μM. For the lowest concentration, total uptake of each FQ was observed but stoichiometric fluoride release was not achieved. Intermediate compounds were detected and identified by LC-MS/MS with a quadrupole time of flight detector analyzer. Biotransformation of FQs by L. portucalensis mainly occurred through a cleavage of the piperazine ring and displacement of the fluorine substituent allowing the formation of intermediates with less antibacterial potency. FQ-degrading microorganisms could be useful for application in bioaugmentation processes towards more efficient removal of contaminants in wastewater treatment plants.

Geographic distribution of cadmium and its interaction with the microbial community in the Longjiang River: risk evaluation after a shocking pollution accident

“…Labrys is also sensitive to other metals (Fe 2+ , Cu 2+ , and Ag + ) 44 . Labrys is an important microbe for the bioremediation of contaminants in wastewater treatment, as it has the ability to biodegrade three of the most used fluoroquinolone antibiotics worldwide: ofloxacin, norfloxacin, and ciprofloxacin 45 . The decreased abundance of Labrys may cause harmful effects to the environment.…”

The biodegradation vs. biotransformation of fluorosubstituted aromatics

“…Ofloxacin was transformed via demethylation of the piperazinyl moiety, followed by two-fold hydroxylation and decarboxylation. No defluorinated metabolite was detected (Amorim et al 2014b). …”

“…FP1, and Rhodococcus sp. S2 in the presence of acetate as a cosubstrate (Amorim et al 2014b;Maia et al 2014). A mixed culture of these three strains released fluoride during successive feedings of ciprofloxacin at a steady, but lower rate compared to the elimination of the substrate itself.…”

“…At higher concentrations, only incomplete transformation occurred, but the substrate was partly defluorinated (22 %). Two metabolites were detected, suggesting oxidative defluorination and hydroxylation at C-6, and desethylenation of the piperazinyl group (Amorim et al 2014b).…”

“…S2 transformed norfloxacin and liberated 60.5 % of the fluorine supplied during four successive feedings in the form of fluoride (Maia et al 2014). L. portucalensis F11 alone completely removed up to 2 μM of norfloxacin from the medium, but achieved a defluorination of only about 38 % (Amorim et al 2014b). The strain was able to defluorinate norfloxacin by hydroxylation at the C-6 position.…”