Decolorization of synthetic dyes by crude laccase from a newly isolated Trametes trogii strain cultivated on solid agro-industrial residue

Abstract

A new dye-decolorizing white-rot fungus was isolated and identified as Trametes trogii based on its ITS-5.8S rRNA gene sequence analysis and morphological characteristics. Laccase was the only lignolytic enzyme produced by this strain during solid substrate fermentation (SSF) in soybean cake, a solid agro-industrial residue used for the first time in enzyme production. The extracellular crude enzyme from T. trogii in solid substrate fermentation showed good activity in synthetic dye color removal, decolorizing 85.2% Remazol Brilliant Blue R (50 mg l(-1)), 69.6% Reactive Blue 4 (35 mg l(-1)), and 45.6% Acid Blue 129 (83.3 mg l(-1)) without the addition of redox mediators, 90.2% Acid Red 1 (10 mg l(-1)), and 65.4% Reactive Black 5 (18.3 mg l(-1)) with the addition of 1mM 1-hydroxybenzotriazole in 30 min. Native polyacrylamide gel electrophoresis (Native-PAGE) of the crude enzyme and effects of laccase inhibitors on decolorization corroborated the laccase as the major enzyme involved in the decolorization of dyes. The comparison of color removal by the crude culture filtrates and by the whole fungal culture on the solid substrate revealed the former was more advantageous.