Mechanistic study of degradation of basic violet 3 by Citrus limon peroxidase and phytotoxicity assessment of its degradation products

• In the present investigation, an efficient degradation of basic violet 3 was attained within 5 min by Citrus limon peroxidase.
• The enzyme was isolated from peels and used without any purification, which makes the process cheaper.
• A degradation scheme was proposed on the basis of UPLC/MS analysis.
• Reduction in phytotoxicity was evaluated using Zea mays as test organism.

The current study evaluates the potential of partially purified Citrus limon (lemon) peroxidase in the decolorization of a common synthetic triphenylmethane class dye; basic violet 3. Some important process parameters were optimized by OFAT methodology. Along with this, the effect of metal ions and mediators on the process of decolorization was also evaluated. The maximum decolorization (96.34%) of 7.5 mg/L dye was achieved at 42 U/mL of enzyme dose, 0.25 mM of H2O2 and 0.5 mM of p-coumaric acid. The pH, temperature and time for maximum decolorization were recorded to be 4.5, 45 °C, and 5 min, respectively. The presence of metal ions did not exert any drastic influence on the process of decolorization, ensuring it suitable for industrial applications. The optimization and interactive effect of pH, enzyme dose, and dye concentration for maximum decolorization was also investigated by RSM through central composite design matrix. UPLC/MS analyses were performed to identify the degradation products. As a result a mechanistic pathway for degradation of basic violet 3 was proposed. It was also found that degraded products of basic violet 3 showed less phytotoxicity than the dye itself, using Zea mays as test organism.