The extracellular laccase produced by the ascomycete Trichoderma atroviride was purified and characterized and its ability to transform phenolic compounds was determined. The purified laccase had activity towards typical substrates of laccases including 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), dimethoxyphenol (2,6-DMP), syringaldazine and hydroquinone. The enzyme was a monomeric protein with an apparent molecular mass of 80 kDa and an isoelectric point of 3.5. The pH optima for the oxidation of ABTS and 2,6-DMP were 3 and 5, respectively, and the optimum temperature was 50 C with 2,6-DMP. The laccase was stable at slightly acidic pH (4 and 5). It retained 80% of its activity after 4 h incubation at 40 degrees C. Under standard assay conditions, Km values of the enzyme were 2.5 and 1.6 mM towards ABTS and 2,6-DMP, respectively. This enzyme was able to oxidize aromatic compounds present in industrial and agricultural wastewater, as catechol and o-cresol, although the transformation of chlorinated phenols required the presence of ABTS as mediator. (C) 2009 Elsevier Ltd. All rights reserved.