Abstract: The biodegradation characteristic and mechanism of trinitrotoluene (TNT) by a bacterial consortium S consisted of Klebsiella sp. S1 and Burkholderia sp. S2 were investigated by shaking-flask culture. The results show that the consortium S can completely biodegrade 0.1 g/L TNT in solution in the presence of both external carbon and nitrogen sources, whereas the biodegradation efficiency of TNT reaches 80% and 12%, respectively, with external carbon source only and nitrogen source only. Highly active nitroreductase was detected in the S1 catalyst system. This enzyme transformed TNT into a condensation product, diazodinitrotoluene, which was further degraded through ring cleavage catalyzed by the combined action of highly active toluene dioxygenase and catechol dioxygenase produced in the case of coexistence of S1 and S2. Nitro groups in TNT were released during the ring cleavage of diazodinitrotoluene, resulting in the formation of NO₂^–, which was further oxidized into NO₃^–. This bacterial consortium has greater potentials in biodegradation of TNT than the single bacterium.

Key words: trinitrotoluene, bacterial consortium, biocatalytic degradation, oxidative ring cleavage