Purification and Characterization of Pleurotus florida Laccase (L1) involved in the Remazol Brilliant Blue R (RBBR) Decoloration

Pleurotus florida produces two extracellular laccase (L1 and L2) isoenzymes and the L1 isoenzyme is dominantly involved in the dye decoloration process. L1 isoenzyme was successfully purified to 6.4 fold with a yield of 36% and had a specific activity of 52.6 U mg of protein. The purified laccase was monomeric with an apparent molecular mass of ≈54 kDa. The optimum pH and temperature of the LI isoenzyme was found to be around 5.5 and 50oC, respectively. L1 isoenzyme showed a half life of 2 h at 60 oC and at 4 h it retained around 25% residual activity. The kinetic parameters suggest that the order of affinity towards the tested substrates was syringaldazine > ABTS > DMP > guaiacol. Interestingly, L1 isoenzyme was not significantly inhibited by chloroform and benzene, whereas above 50% of laccase activity was inhibited by acetone, dimethyl sulfoxide and methanol.