Purification and characterization of an extracellular laccase from the anthracene-degrading fungus Fusarium solani MAS2

An extracellular laccase was purified from the culture medium of the non-white rot, anthracene-degrading fungal strain Fusarium solani MAS2. Both native PAGE and SDS–PAGE revealed one single band corresponding to a molecular weight of about 72 kDa. Treatment with endoglycosidase H reduced the molecular weight by 12%. The purified laccase maintained stable at pH 3–11 and up to 50 °C. The highest activity was detected at pH 3.0 and at 70 °C. The enzyme retained 46.2–97.2% of it activity in the presence of 20 mM Pb2+, Ni2+, Cr3+, and its activity was enhanced in the presence of 20 mM Hg2+. The laccase retained more than 50% of its activity in the presence of 5% acetone, acetonitrile, dimethyl sulphoxide (DMSO), ethanol and methanol. The kinetic constants (Km and kcat) showed that 2,6-dimethoxyphenol (DMOP) and 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) diammonium salt (ABTS) were the more effective substrates rather than catechol and guaiacol. The novel properties of this laccase suggest its potential for biotechnological and environmental applications.