Biodegradation of TNT (2,4,6-trinitrotoluene) by Phanerochaete chrysosporium

Abstract

Extensive biodegradation of TNT (2,4,6-trinitrotoluene) by the white rot fungus Phanerochaete chrysosporium was observed. At an initial concentration of 1.3 mg/liter, 35.4 +/- 3.6% of the [14C]TNT was degraded to 14CO2 in 18 days. The addition of glucose 12 days after the addition of TNT did not stimulate mineralization, and, after 18 days of incubation with TNT only, about 3.3% of the initial TNT could be recovered. Mineralization of [14C]TNT adsorbed on soil was also examined. Ground corncobs served as the nutrient for slow but sustained degradation of [14C]TNT to 14CO2 such that 6.3 +/- 0.6% of the [14C]TNT initially present was converted to 14CO2 during the 30-day incubation period. Mass balance analysis of liquid cultures and of soil-corncob cultures revealed that polar [14C]TNT metabolites are formed in both systems, and high-performance liquid chromatography analyses revealed that less than 5% of the radioactivity remained as undegraded [14C]TNT following incubation with the fungus in soil or liquid cultures. When the concentration of TNT in cultures (both liquid and soil) was adjusted to contamination levels that might be found in the environment, i.e., 10,000 mg/kg in soil and 100 mg/liter in water, mineralization studies showed that 18.4 +/- 2.9% and 19.6 +/- 3.5% of the initial TNT was converted to 14CO2 in 90 days in soil and liquid cultures, respectively. In both cases (90 days in water at 100 mg/liter and in soil at 10,000 mg/kg) approximately 85% of the TNT was degraded. These results suggest that this fungus may be useful for the decontamination of sites in the environment contaminated with TNT.