Biological removal of explosive 2,4,6-trinitrotoluene byStenotrophomonas sp. OK-5 in bench-scale bioreactors

The biological removal of 2,4,6-trinitrotoluene (TNT) was studied in a bench-scale bioreactor using a bacterial culture of strain OK-5 originally isolated from soil samples contaminated with TNT. The TNT was completely removed within 4 days of incubation in a 2.5 L benchscale bioreactor containing a newly developed medium. The TNT was catabolized in the presence of different supplemented carbons. Only minimal growth was observed in the killed controls and cultures that only received TNT during the incubation period. This catabolism was affected by the concentration ratio of the substrate to the biomass. The addition of various nitrogen sources produced a delayed effect for the TNT degradation. Tween 80 enhanced the degradation of TNT under these conditions. Two metabolic intermediates were detected and identified as 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene based on HPLC and GC-MS analyses, respectively. Strain OK-5 was characterized using the BIOLOG system and fatty acid profile produced by a microbial identification system equipped with a Hewlett packard HP 5890 II gas chromatograph. As such, the bacterium was identified as aStenotrophomonas species and designated asStenotrophomonas sp. OK-5.