Mechanism of enzymatic degradation of the azo dye Orange II determined by ex situ 1H nuclear magnetic resonance and electrospray ionization-ion trap mass spectrometry

Abstract

Removal of azo dye effluents generated by textile photography industries is a main issue in wastewater treatment. Enzymatic treatment of dyes appears to be one of the most efficient processes for their degradation. The elucidation of degradation pathways is of special interest considering health and environmental priorities. Ex situ nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization (ESI)-ion trap mass spectrometry performed directly on incubation medium have been used for the first time to follow kinetics of sulfonated azo dye Orange II enzymatic degradation. Nine transformation products were identified using these complementary analyses performed ex situ without any prior treatment. Three types of cleavage are proposed for the degradation pathway: (i) a symmetrical splitting of the azo linkage that leads to the formation of 4-aminobenzenesulfonate (and 1-amino-2-naphthol, not detected); (ii) an asymmetrical cleavage on the naphthalene side that generates 1,2-naphthoquinone and 4-diazoniumbenzenesulfonate as products, with the latter one being transformed into 4-hydroxybenzensulfonate; and (iii) a third degradation pathway that leads to 2-naphthol and 4-hydroxybenzenesulfonate. Moreover, three other intermediates have been identified. This study, which constitutes the first concomitant use of (1)H NMR spectroscopy and ESI-ion trap mass spectrometry in this field, illustrates the indubitable interest of the ex situ approach.

Involvement of ligninolytic enzymes of Myceliophthora vellerea HQ871747 in decolorization and complete mineralization of Reactive Blue 220

“…All these, generally follow two main routes as proposed by several studies: symmetrical or asymmetrical cleavage of azo bonds. Also few authors suggested co-existence of both the pathways [49]. Based on the identification of intermediates it was obvious that M. vellerea HQ871747 has asymmetrically cleaved RB220.…”

Transformation pathway of Remazol Brilliant Blue R by immobilised laccase

“…The identification of the metabolites produced during biodegradation as well as toxicity studies must be done to ensure the safety of the laccase-treated effluents. However, so far only a few studies regarding the metabolic pathway of azo dye degradation by ligninolytic enzymes have been performed (López et al, 2004;Martins et al, 2002Martins et al, , 2003Pereira et al, 2009;Svobodová et al, 2007). The aim of the present work was to determine the biotransformation products resulting from the laccase treatment of the anthraquinonic dye RBBR.…”

Decolorization of Acid Red 27 and Reactive Red 2 by Enterococcus faecalis under a batch system

“…Color is the first contaminant in wastewater, which should be recognized and has to be removed before it can be discharged into the environment (Miao 2005). Physicochemical methods used for color removal of the effluents are effective, but they show disadvantages in terms of operational problems, high cost, and sludge production (Kapdan et al 2000;Ló pez et al 2004;Kodam et al 2005). Moreover, those methods use more energy and chemicals than biological processes (Miao 2005).…”