Bioremediation with the fungus Pleurotus ostreatus

Tetracyclines are found at ppm levels in the wastes of intensively reared animals, even after the due storage period. Therefore, setting up techniques to remove and degrade antibiotics drugs in animal waste and soils, is a main goal to prevent or reduce their harmful environmental effects. Bioremediation, aimed to eliminate contaminant by natural processes, with low environmental impact and costs, is one of the most promising approaches and exploits the degradative ability of many microorganisms from the rhizosphere, including fungi and bacteria. As basidiomycetes fungi, in particular the ligninolytic ones, are able to degrade a wide variety of organic compounds and environmental pollutants, this project is aimed to evaluate the possible ability of Pleurotus ostreatus in removing and degrading Oxytetracycline, starting from an experimental laboratory model, under controlled conditions. This work was performed with Emanuela Galli, from the Centre for Research IBAF-CNR (Research Area of Rome 1), by utilizing a strain from the International Bank of edible saprophytic fungi.

 

 

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-decarboxamido-oxytetracycline) is proposed. Experimental conditions excluded OTC abiotic degradation; the degradation by extracellular laccase was also experimentally discarded.