Oxidation of phenol and polyphenolic compounds using aqueous extracts of the mushroom Agaricus bisporus residual culture medium (compost) was studied. Laccase was identified as the main activity in the aqueous extracts. These were applied without further purification to substrates such as guaiacol, 2,3-dimethoxyphenol, ventril alcohol, aniline and phenol. The relative activity of the compost extract, measured in terms of the time required to oxidize the substrate was 2,6-dimethoxyphenol > guaiacol > phenol > ventryl alcohol > aniline, with the highest activity corresponding to 2,6-dimethoxyphenol and the lowest to aniline. In oxidation experiments with 1 and 5 mg/ml of phenol, enzymatic oxidation occurred within 48 and 125 h, respectively. The pH conditions of dephenolization processes were also studied using the mushroom extracted laccase. Optimal oxidation of phenol was observed at pH of 7. The results demonstrate that the residual compost, after culturing A. bisporus, is a potential source of laccase that could become a cost-effective waste management alternative for some phenolic compounds. (C) 2001 Elsevier Science Ltd. All rights reserved.