Mechanistic study of a diazo dye degradation by Soybean Peroxidase

Abstract

BackgroundEnzyme based remediation of wastewater is emerging as a novel, efficient and environmentally-friendlier approach. However, studies showing detailed mechanisms of enzyme mediated degradation of organic pollutants are not widely published.ResultsThe present report describes a detailed study on the use of Soybean Peroxidase to efficiently degrade Trypan Blue, a diazo dye. In addition to examining various parameters that can affect the dye degradation ability of the enzyme, such as enzyme and H2O2 concentration, reaction pH and temperature, we carried out a detailed mechanistic study of Trypan Blue degradation. HPLC-DAD and LC-MS/MS studies were carried out to confirm dye degradation and analyze the intermediate metabolites and develop a detailed mechanistic dye degradation pathway.ConclusionWe report that Soybean peroxidase causes Trypan Blue degradation via symmetrical azo bond cleavage and subsequent radical-initiated ring opening of the metabolites. Interestingly, our results also show that no high molecular weight polymers were produced during the peroxidase-H2O2 mediated degradation of the phenolic Trypan Blue.

Differential Degradation and Detoxification of an Aromatic Pollutant by Two Different Peroxidases

“…However, SRB dye degradation by CPO was optimal at pH 2 and further increases in pH caused the degradation to decrease dramatically until it reached almost 25% at pH 4 ( Figure 3A). These results are in agreement with previously published studies with SBP, where maximum degradation of Trypan Blue [35], Crystal Ponceau 6R [36], Amido Black [37], and Remazol…”

“…As can be seen from Figure 3C, there was no significant change in the degradation of the SRB dye by SBP at H2O2 concentrations ranging from 0.2 mM to 16.5 mM. These results, along with those previously reported, suggest that SBP is a remarkably stable enzyme, compared to CPO, as it can tolerate high concentrations of strong oxidants, such as H2O2 [35,36,42].…”

“…However, when 1-hydroxybenzotriazole (HOBT), one of the most commonly used redox mediators, was added to the reaction mixture, rapid and efficient SRB dye degradation was observed ( Figure 2A and Figure 2B). This absolute requirement of HOBT was not observed in the SBP-degradation of many other dyes [27,35], but is consistent with peroxidase-mediated degradation of Crystal Ponceau 6R and ThT dyes [27,36]. Optimization of HOBT concentration for efficient SRB dye degradation showed that 50 μM HOBT was the optimum amount of redox mediator for SBP-based degradation, whereas the CPO-based reaction showed the best degradation of SRB dye at 167 μM HOBT ( Figure 2B).…”

“…The proposed structures of the chlorinated intermediates (based on LC-MS/MS analyses) are shown in Figure 10B. Additionally, the presence of dichlorinated intermediates was further confirmed by the characteristic chlorine isotope signatures 35 Cl and` 37 Cl. For example, the 571 m/z intermediate showed several lines, which could be interpreted as a combination of chlorine isotopes representing M + , M +2 , and M +4 , as illustrated in Figure 10B.…”

Sweet Lime-Mediated Decolorization of Textile Industry Effluents

“…These enzyme-based methods applied in dye degradation are cost-effective, easily controllable, and eco-friendly. In this regard, peroxidases (PODs) belonging to the class of oxidoreductases are considered very important [19].…”