Mechanism of Reactive Orange 16 degradation with the white rot fungus Irpex lacteus

The study focuses on the Reactive Orange 16 (RO16) degradation products obtained by fungal treatment of the dye. Eighty percent of dye decolorization was achieved within 24 h by Irpex lacteus cultures immobilized on polyurethane foam (PUF). Dye degradation products were investigated using LC–MS analysis. Three compounds were identified as the dye intermediates: 6-acetamido-3,4-dioxo-3,4-dihydronaphthalene-2-sulfonate (m/z 294), (E)-2-(4-acetamidophenyl)-1-carboxyethenesulfonate (m/z 284), and 4-(2-hydroxyethylsulfonyl)phenolate (m/z 201). Despite significant laccase activities detected in the fungal cultures, no backward polymerization of the reaction products resulting in recurrent colorization was observed after fungal treatment of the dye solution.