| Blue and yellow laccases were purified from the white-rot fungus Trametes versicolor. After purification, the specific activity of blue laccase was 11.59 mukat/mg versus 1.75 mukat/mg for yellow laccase. The blue laccase displayed optimal activity at 75°C and pH 3.0. The yellow laccase exhibited optimal activity at 65°C and pH 3.5. The carbohydrate content was 30.9% for the blue laccase and 38.5% for the yellow laccase. The blue laccase was more stable than the yellow laccase above 65°C. Both blue and yellow laccases demonstrated typical Michaelis-Menten kinetics using 2,6-dimethoxyphenol (DMOP), 2,2-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS) and syringaldazine (SGA) as substrates. The blue laccase showed highest catalytic efficiency towards ABTS while the yellow laccase exhibited highest catalytic efficiency towards DMOP. Presence of 1-hydroxynenzotriazole (HOBT) could significantly enhance transformation of the lignin model compound, veratryl alcohol, and the azo dye, Orange II by both blue and yellow laccases.;Modifications of the blue laccase included crosslinking of the enzyme with poly(ethylene glycol) diglycidyl ether, covalent attachment of the enzyme to tresylated monomethoxy poly(ethylene glycol) (tMPEG), and immobilization of the enzyme to cellulose (cotton cloth). Crosslinked blue laccase exhibited optimal activity at 45°C and pH 3.0 and showed higher thermostability than native blue laccase at 45°C and 55°C. Immobilized laccase displayed optimal activity at 25°C and pH 4.0 and demonstrated higher thermostability and tolerance for organic solvents than native blue laccase.;Native and immobilized laccases were applied to dye decolorization, dechlorination of chlorophenol and removal of endocrine disruptors. HOBT and 3-amino- N-hydroxyphthalimide were the best mediators for Orange II decolorization by laccase. Dechlorination of pentachlorophenol by the blue laccase was greatly enhanced by coupling co-substrates and HOBT. Immobilized blue laccase showed much higher efficiency than native blue laccase in transformation of bisphenol A, 4-tert-octylphenol and nonylphenol in presence of mediators. Temperature and concentration of organic solvents played important roles in enzymatic removal of endocrine disruptors. |
