Residual compost of Agaricus bisporus as a source of crude laccase for enzymic oxidation of phenolic compounds

Oxidation of phenol and polyphenolic compounds using aqueous extracts of th e 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 acti vity of the compost extract, measured in terms of the time required to oxid ize the substrate was 2,6-dimethoxyphenol > guaiacol > phenol > ventryl alc ohol > aniline, with the highest activity corresponding to 2,6-dimethoxyphe nol 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-effect ive waste management alternative for some phenolic compounds. (C) 2001 Else vier Science Ltd. All rights reserved.