Cametabolic biotransformation of trinitrotoluene (tnt) supported by aromatic and non-aromatic cosubstrates

Abstract

A microbial consortia was isolated from trinitrotoluene (TNT) contaminated soil and cultured in media supplemented with structurally similar (aromatic) or non-aromatic cosubstrates and TNT to examine their impact on cometabolic TNT biotransformation. A microbial inoculum with 10 5 CFU/ml with TNT concentrations of 5, 10, 30 and 50 ppm in separate triplicate cultures revealed maximum TNT biotransformations of 23, 21, 9 and 3%, respectively, after 9 days. A larger inoculum (l0 7CFU/ml) resulted in transformation of TNT concentrations of 8, 15, 22 and 30 ppm by 71, 54, 50 and 38%, respectively. Cultures supplemented with benzene, nitrobenzene or toluene revealed no enhancement of TNT biotransformation rates or extents over those in culture with TNT as sole carbon source. With glucose and citric acid at 30 mg/l, TNT biotransformations of 56 and 51%, respectively, were obtained. With glucose or citric acid at 3000 mg/l, 100% transformation of 30ppm TNT was realized in 24 hours and of 100ppm TNT in 72hrs. Metabolites identified included 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,6-diamino-4-nitrotoluene, and 2,4-dinitrotoluene; analysis also demonstrated that TNT disappearance paralleled glucose utilization and cell growth.