Investigation on Fe²⁺-dependent Reaction on Methyl Orange Biodecolorization by Daedalea dickinsii

The investigation of Fe²⁺-dependent reaction on methyl orange (MO) biodegradation by brown-rot fungus Daedalea dickinsii was performed to evaluate the involvement of Fenton reaction. The MO degradation (final concentration 75 mg/L) was evaluated for incubation period at 0, 7, 14, 21, and 28 days in mineral salt media with and without Fe²⁺. UV-Vis Spectrophotometer and LC-TOF/MS were used for degradation analysis. The highest MO decolorization by D. dickinsii was approximately 77.1% and 60.5% in medium without and with Fe²⁺, respectively, occurred for 28 days incubation. It indicated that the optimum decolorization was obtained in medium without Fe²⁺, which assumed that Fe²⁺ dependent reaction might be not enhanced decolorization of MO by D. dickinsii. Based on LC-TOF/MS analysis, 2-hydroxy-4((2-hydroxy-4(methylamino) phenyl) diazinyl) phenolate (C13H12N3O3), and 4-(2-(4-(dimethylamino)-2,3,5,6-tetramethoxy phenyl) hydrazinyl)-2,3,5,6tetramethoxy benzenesulphonate (C22H32N3O11S) were detected as metabolites of MO degradation. C13H12N3O3 was a transformation product of demethylation, hydroxylation and desulfonation, while C22H32N3O11S was a product of methoxylation. This study indicated that the methyl orange (MO) decolorization was a hybrid process between Fenton's mechanism and enzymatic activity.