Transformation of 2,4,6-trinitrotoluene (TNT) by Raoultella terrigena

Manufacture of nitroorganic explosives generates toxic wastes leading to contamination of soils and waters, especially groundwater. For that reason bacteria living in environments highly contaminated with 2,4,6-trinitrotoluene (TNT) and other nitroorganic compounds were investigated for their capacity for TNT degradation. One isolate, Raoultella terrigena strain HB, removed TNT at concentrations between 10 and 100 mg l(-1) completely from culture supernatants under optimum aerobic conditions within several hours. Only low concentrations of nutrient supplements were needed for the cometabolic transformation process. Radioactivity measurements with ring-labelled C-14-TNT detected about 10-20% of the initial radioactivity in the culture supernatant and the residual 80-90% as water-insoluble organic compounds in the cellular pellet. HPLC analysis identified aminodinitrotoluenes (2-ADNT, 4-ADNT) and diaminonitrotoluenes (2,4-DANT) as the metabolites which remained soluble in the culture medium and azoxy-dimers as the main products in the cell extracts. Hence, the new isolate could be useful for the removal of TNT from contaminated waters.