An extracellular yellow laccase from white rot fungus Trametes sp. F1635 and its mediator systems for dye decolorization.

A novel extracellular laccase was purified from fermentation broth of the white rot fungus Trametes sp. F1635 by a three-step protocol including two consecutive ion-exchange chromatography steps on DEAE-Sepharose and SP-Sepharose, and a final gel-filtration on Superdex 75. The purified laccase (TsL) was a monomeric protein with the molecular mass of 64.8 kDa. It demonstrated high oxidation activity of 4.00 × 104 U/mg towards ABTS. Its N-terminal amino acid sequence was AIGPVADLTIINNAV which was unique and sharing high similarity of other fungal laccases. TsL was a yellow laccase based on absorption spectrum analysis. It demonstrated an acidic pH optimum of 2.6 and temperature optimum of 50 °C towards ABTS. The Km and Vmax values towards ABTS were estimated to 18.58 μM and 1.35 μmol/min, respectively. TsL manifested effective decolorization activity towards eriochrome black T (EBT), remazol brilliant blue R (RBBR), malachite green (MG), and eriochrome black T (EBT) (over 60%). Violuric acid (VA) and acetosyringone (AS) were the optimal mediators for the laccase in dye decolorization. Results suggest that TsL demonstrates great potential for dye decolorization and water treatment.