Transformation and mineralization of 2,4,6-trinitrotoluene by the white rot fungus Irpex lacteus

Abstract

Unlike other 2,4,6-trinitrotoluene (TNT)-degrading white rot fungi, including Phanerochaete chrysoporium, initial metabolism of TNT by Irpex lacteus was found to occur through two different transformation pathways. Metabolites of the nitro group reduction pathway were confirmed with the standard compounds, and the formation of hydride-Meisenheimer complex of TNT (H(-)-TNT) formed in the denitration pathway was identified with LC/MS and by LC/photodiode array (PDA) detection. The molecular weight of the H(-)-TNT complex was identified as 228 m/z, and the UV-visible absorption spectrum, recorded with a PDA detector, proved the identity of this metabolite (RT, 18.7 min; lambda(max) 254, 474, 557 nm) by comparison with the authentic synthetic H(-)-TNT (RT 18.7 min; lambda(max) 261, 474, 563 nm). Mineralization of [U-(14)C]TNT by I. lacteus was also measured in static and shaken cultures. The mineralization rate of TNT in the static culture was higher than that in the shaken culture, and addition of Tween 80 (final concentration 1%) enhanced the mineralization of TNT in the static culture, resulting in 30.57% of CO(2) evolution from the radiolabeled TNT added. The high TNT mineralization capability of I. lacteus seemed to be the result of simultaneous utilization of the denitration pathway, which is more favorable for the ring cleavage and mineralization of TNT, together with the nitro group reduction pathway.