Detoxification of substituted phenols by oxidoreductive enzymes through polymerization reactions

Laccases from the fungi Rhizoctonia praticola and Trametes versicolor, horseradish peroxidase and tyrosinase were evaluated for their ability to polymerize phenolic contaminants. Phenol removal by polymerization depended on chemical structure and concentration of the substrate, reaction mixture pH, enzyme activity, incubation time and temperature. The enzymes were active over a broad pH and temperature range. The transformation efficiency of 2,4-dichlorophenol, 2,3,5-trichlorophenol and pentachlorophenol decreased with increasing number of chlorine atoms. The laccase from T. versicolor was approximately 10 times more efficient than laccase from R. praticola. The precipitates formed during polymerization of 2,4-dichlorophenol were a mixture of oligomers with molecular weights up to 800 daltons. Mass spectra showed the loss of chlorine atoms during polymerization.