Biodegradation of a model azo disperse dye by the white rot fungus Pleurotus ostreatus

Disperse Orange 3, 4-(4-nitrophenylazo)aniline, was chosen as a model to study biodegradation of azo dyes by the white-rot fungus Pleurotus ostreatus (strain Florida) which was grown in submerged culture under controlled conditions. Degradation was investigated using a commercial preparation of Disperse Orange 3 that contained 20% dye plus dispersing agents, and an high-performance liquid chromatography purified preparation of the dye. The metabolites generated by Pleurotus ostreatus were identified as 4-nitroaniline, 4-nitrobenzene, 4-nitrophenol, and 4-nitroanisole. Veratryl alcohol, a redox mediator for lignin peroxidase of white-rot fungi, and its oxidant veratraldehyde were also detected in cultures grown in the presence of Disperse Orange 3. 4-Nitroanisole was the major metabolite when 4-nitrophenol was incubated with Pleurotus ostreatus. Kinetic profiles of these degradation products were determined and a partial degradation pathway is proposed.