Triphenylmethane dye decoloration using hydrogen peroxide-resistant manganese peroxidase

Abstract:

[Objective] We produced a novel manganese-dependent peroxidase (MnP) by Trametes sp. SQ01 and studied its resistance of MnP to hydrogen peroxide, substrate specificity and ability of decolorizing triphenylmethane dyes. [Methods] MnP was purified through acetone precipitation and DEAE-celluose 52 anion-exchange chromatography. The resistance of MnP against H2O2 and dye decolorization were measured with a UV-visible spectrophotometer. [Results] The homogenous MnP has been obtained through two-step purification. The optimum pH and temperature for the purified MnP were 4.5 and 70 °C, respectively. The enzyme was highly stable in the pH range 3.0?8.0. The enzyme oxidizes various substrates in the presence of manganese, such as 2,6-dimethoxyphenol, guaiacol, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and H2O2, simultaneously, the MnP also regards Mn2+ as its substrate. Among all the substrates tested, the optimum was H2O2 (Km, 3.7?μmmol/L). Interestingly, the enzyme was resistant to H2O2 bleaching. The enzyme retains 70% integrity of its heme after incubation with 2.5 mmol/L H2O2 for 60 min. All of the tested dyes could be discolored by MnP, among which Crystal violet was observed with the highest decolorization rate at 65.8%. The effects of Mn2+ and H2O2 on dye decolorization by MnP were also studied, which revealed that both H2O2 and Mn2+ had less influence on the decolorization of Remazol Brilliant Blue R (RBBR) than Malachite Green. [Conclusion] The resistance of MnP to hydrogen peroxide and its ability of decolorizing triphenylmethane dyes demonstrated its potential application on dye decolorization.

Key words:Manganese peroxidase (MnP), Hydrogen peroxide, Triphenymethane dye, Dye decolorization