Influence of redox mediators and metal ions on synthetic acid dye decolourization by crude laccase from Trametes hirsuta

On the other hand, the stability of laccase against several metal ions, normally found in textile wastewater, was assessed. Laccase was stable at a concentration of 1 mM for 7 d against all the metal ions tested except for Zn+2, CrO4-2, Cd+2, Cr2O7-2, Fe+2, Cu+2 and especially Hg+2. When the concentration was increased to 10 mM laccase stability decreased against all the metals assayed, in particular against Fe+2. In addition, the effect of metal ions on the decolourization process was also studied. It was found that Hg+2 inhibited the dye decolourization process, being the presence of HBT absolutely required for dye decolourization.