Purification and characterization of a thermotolerant laccase isoform in Trametes trogii strain and its potential in dye decolorization

•The purified laccase of Trametes trogii S0301 was thermotolerant.•The purified laccase was highly resistant to many metal ions.•The purified laccase showed efficient decolorization without redox mediators.•The laccase gene was cloned.

Using response surface methodology, the maximum laccase activity of 122.9 U ml−1 was obtained in Trametes trogii S0301. The major isoform of the laccase secreted in the optimized medium was purified by 4-fold to a specific activity of 352.1 U mg−1 protein. The laccase (a molecular mass of 56 kDa), acted optimally at pH 3.0 and exhibited an optimum temperature of 45 °C using ABTS as substrate, with the half-life at 60 °C and 75 °C for 3 h and 10 min, respectively. The purified laccase was highly resistant to Co2+, Cu2+, Zn2+ and Mn2+ (100 mM). In addition, the purified laccase was effective to decolorize malachite green, bromophenol blue, crystal violet and acid red without the addition of redox mediators. Peptide-mass fingerprinting analysis by MALDI-TOF MS showed the purified laccase of T. trogii S0301 was a typical laccase isoform, which shared 99.3% identity with a laccase from Coriolopsis gallica. Further, the full-length DNA of the laccase was cloned based on the highly conservative copper-binding domains using degenerate PCR and TAIL-PCR, and the deduced amino acid sequence of the matured protein matched exactly with the peptides of the purified laccase.