Microbial remediation of NTO in aqueous industrial wastes

The bioremediation of aqueous wastes containing 5-nitro-1,2,4-triazol-3-one (NTO) was investigated. The microorganism used is a Bacillus licheniformis strain, isolated from the contaminated solutions by enrichment techniques. The biodegradation was carried out in the waste (15 g l(-1) NTO) and proceeded through the nitroreduction of NTO, followed by the ring cleavage of the formed primary amine 5-amino-1,2,4-triazol-3-one (ATO). Both steps were optimized and according to the optimal conditions, the nitroreduction of NTO is total in 24 h, while the degradation of ATO requires 2 weeks of incubation. The end products of the biodegradation were carbon dioxide (40%), urea and a polar compound, assumed to be hydroxyurea. A mechanism of ATO ring cleavage was postulated in the light of experimental data, and led us to propose an overall degradation sequence for NTO. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.