Comparative catalytic degradation of a metabolite 3,5-dichloroaniline derived from dicarboximide fungicide by laccase and MnO2 mediators.

A ternary catalysis system was investigated to evaluate the comparative degradation of toxic fungicide metabolite 3,5-dichloroaniline (3,5-DCA) by laccase and MnO2 with mediators. In this study, copper based fungal enzyme laccase (Trametes versicolor origin) and metal catalyst MnO2 with various combinations of phenolic mediators (catechol, syringaldehyde, syringic acid, caffeic acid and gallic acid) were monitored to optimize and screen the better one for 3,5-DCA degradation assay. Catechol showed better potentiality in reduction of 3,5-DCA among the studied mediators. Catechol (2mM) showed the highest reduction rate (99-100%) followed by syringaldehyde (40.51%) with 2U/mL of laccase at 25 °C within 24 h reaction time. Similarly, complete degradation of 3,5-DCA was obtained by catechol (2mM) with 2 mg/mL of MnO2 in MnO2-mediator assay. The notable finding of current study indicated the triggering of catechol for better 3,5-DCA degradation at higher pH condition but inertness in laccase-mediator assay due to laccase destabilization. The reaction pathways of optimized mediator-based catalysis for laccase and MnO2 were proposed. Finally, the optimized laccase-catechol based degradation was considered as a pioneer green catalysis approach to reduce the toxic metabolite 3,5-DCA concentrations in aqueous medium as compared to MnO2-catechol catalysis.