A pH-stable Yellow Laccase from White Rot Fungus Trametes sp.SQ01:Rapid Purification and Characterization

The white rot fungus Trametes sp.SQ01 secretes a high level of laccase in the basal liquid medium without induction.The laccase has been purified to homogeneity through acetate acetone precipitation and DEAE-cellulose 52 anion-exchange chromatography with a final purification fold of 15.4 and an overall yield of 43.6%.The purified enzyme was identified with a molecular mass of 62 kD by SDS gel electrophoresis.The purified enzyme was not blue like the typical laccase but yellow,and had not the basic spectroscopic features of a typical blue laccase.The enzyme oxidized a series of diphenol,creosol and non-phenol,including 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate)(ABTS),catechols,hydropuinone,2,6-dimethoxyphenol(DMP),and guaiacol.With ABTS as a substrate,the optimum pH and temperature for the purified laccase were 4.5 and 70°C,respectively.The enzyme was highly stable in the pH range 3～11,and the most stable under the pH 5.0.The enzyme was stable up to 50°C,and had half-life of 30 min at 60°C.The susceptibility of laccase towards several surfactants,inhibitors and metal cations was also assessed.The enzyme activity was completely inhibited by DTT at the concentration of 1 mmol/L,but 1 mmol/L of SDS activated the laccase activity by 128%.Laccase activity was also inhibited by several metal cations at a 5 mmol/L of concentration,especially Mn2+.The purified enzyme efficiently decolorized Remazol Brilliant Blue R(RBBR) in the absence of added redox mediators.The high production of Trametes.sp.SQ01 laccase as well as its decolorization ability demonstrated its potential application on dye decolorization.