Degradation of the antibiotics norfloxacin and ciprofloxacin by a white-rot fungus and identification of degradation products
2011
Prieto, Ailette | Möder, Monika | Rodil, Rosario | Adrian, Lorenz | Marco-Urrea, Ernest
More than 90% of the antibiotics ciprofloxacin (CIPRO) and norfloxacin (NOR) at 2mgL⁻¹ were degraded by Trametes versicolor after 7days of incubation in malt extract liquid medium. In in vitro assays with purified laccase (16.7nkatmL⁻¹), an extracellular enzyme excreted constitutively by this fungus, 16% of CIPRO was removed after 20h. The addition of the laccase mediator 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt led to 97.7% and 33.7% degradation of CIPRO and NOR, respectively. Inhibition of CIPRO and NOR degradation by the cytochrome P450 inhibitor 1-aminobenzotriazole suggests that the P450 system also plays a role in the degradation of the two antibiotics. Transformation products of CIPRO and NOR were monitored at different incubation times by triple-quadrupole and quadrupole time-of-flight mass spectrometry, and can be assigned to three different reaction pathways: (i) oxidation of the piperazinyl substituent, (ii) monohydroxylation, and (iii) formation of dimeric products.
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