An extracellular laccase with potent dye decolorizing ability from white rot fungus Trametes sp. LAC-01

A novel laccase was purified from fermentation broth of white rot fungus Trametes sp. LAC-01 using an isolation procedure involving three ion-exchange chromatography steps on DEAE-cellulose, SP-Sepharose, and Q-Sepharose, and one gel-filtration step. The purified enzyme (TSL) was proved as a monomeric protein with a Mr of 59 kDa based on SDS-PAGE and FPLC. Partial amino acid sequences were obtained by LC-MS/MS sharing considerably high sequence similarity with that of other laccases. It possessed optimal pH of 2.6 and temperature of 60 °C using ABTS as the substrate. The Km of the laccase toward ABTS was estimated to 30.28 μM at pH 2.6 and 40 °C. TSL manifested considerably high oxidizing activity toward ABTS, but was avoid of degradative activity toward benzidine, caftaric acid, etc. It was effective in the decolorization of phenolic dyes - Bromothymol Blue and Malachite Green with decolorization rate higher than 60% after 24 h of incubation. Adjunction of Cu2+ with the final concentration of 2.0 mmol/L significantly activated laccase production with a steady high level of 275.8-282.2 U/mL in 96-144 h. The high yield and short production period makes Trametes sp. LAC-01 and TSL potentially useful for industrial and environmental application and commercialization.