Biodegradation of oxytetracycline by Pleurotus ostreatus mycelium: a mycoremediation technique

Oxytetracycline (OTC) is administered in high doses to livestocks and enters the environmental compartments as a consequence of animal waste disposal. As a first step in setting up a useful mycoremediation technique, an OTC lab degradation test was performed in liquid medium using the ligninolytic fungus Pleurotus ostreatus. OTC disappearance in culture medium was clearly evident as early as the third day of exposure onwards, with an almost complete removal after 14 d. The drug removal was mediated by fungal absorption in the mycelia, where the OTC molecule underwent a degradation step, as demonstrated by mass spectrometry analyses. A putative degradation product, ADOTC (2-acetyl-2-decarboxamidooxytetracycline) is proposed. Experimental conditions excluded OTC abiotic degradation; the degradation by extracellular laccase was also experimentally discarded.