Extracellular enzyme activities during humic acid degradation by the white rot fungi<i>Phanerochaete chrysosporium</i>and<i>Trametes versicolor</i>

Abstract

The relationship between humic acid biodegradation and extracellular lignin peroxidase and Mn-dependent peroxidase activities of two white rot fungi, Phanerochaete chrysosporium and Tranetes versicolor, reported to be lignin degraders, was examined. In experimental conditions promoting culture aeration, particularly with T. versicolor no extracellular peroxidase activity could be detected unless humic acids were included in the culture medium. In the presence of humic acids, appreciable enzymatic activities were determined in the culture filtrate of the two fungi. However, T. versicolor was a more effective degrader than P. chrysosporium, and mineralization assays on synthetic humic acids with culture filtrates showed the important role played by Mn2+. The surfactant properties of humic acids are suggested to be responsible for the increase of enzymatic activities.