Metabolites from the biodegradation of triphenylmethane dyes by Trametes versicolor or laccase

The feasibility of degrading triphenylmethane dyes by Trametes versicolor and laccase has been investigated for the following dyes: Acid Fuchsin, Brilliant Green 1, Basic Fuchsin, Methyl Green or Acid Green 16. The toxicity level of triphenylmethane dyes is linked to their basic character, but significant detoxification is obtained when there is biodegradation. Identification of enzymatic degradation products by 1H NMR made it possible to propose a general rule for the laccase attack on triphenylmethane compounds. The enzyme completely degrades the molecular part of the canonical resonance substructures of dyes, because no N-substituted, mono-N and di-N,N substituted p-amine aromatic residues seem to be wholly degraded. No enzymatic degradation is observed in the cases of either the non-substituted or trisubstituted-N,N,Np-amine aromatic residues. On the other hand, for all the dyes tested, no aromatic residues are detected after fungal treatment; this means that T. versicolor is more capable of performing further degradation than is laccase. The results of this study demonstrated that compounds with a triphenylmethane structure can be degraded by T. versicolor even if they are highly toxic. The enzyme laccase plays an important role in the attack on the structure and a general rule for predicting which products would be obtained after the enzymatic treatment is suggested.