Identification of HYDROXYLAMINO-DINITROSO-1,3,5TRIAZINE as a Transient Intermediate Formed During the Anaerobic Biodegradation of HEXAHYDRO-1,3,5-TRINITRO-1,3,5TRIAZINE (original) (raw)
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Applied and Environmental Microbiology, 2000
The biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in liquid cultures with municipal anaerobic sludge showed that at least two degradation routes were involved in the disappearance of the cyclic nitramine. In one route, RDX was reduced to give the familiar nitroso derivatives hexahydro-1-nitroso-3,5dinitro-1,3,5-triazine (MNX) and hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX). In the second route, two novel metabolites, methylenedinitramine [(O 2 NNH) 2 CH 2 ] and bis(hydroxymethyl)nitramine [(HOCH 2 ) 2 NNO 2 ], formed and were presumed to be ring cleavage products produced by enzymatic hydrolysis of the inner CON bonds of RDX. None of the above metabolites accumulated in the system, and they disappeared to produce nitrous oxide (N 2 O) as a nitrogen-containing end product and formaldehyde (HCHO), methanol (MeOH), and formic acid (HCOOH) that in turn disappeared to produce CH 4 and CO 2 as carbon-containing end products.
Biodegradation of Hexahydro-1, 3, 5-Trinitro-1, 3, 5-Triazine
Applied and …
In previous work, we found that an anaerobic sludge efficiently degraded hexahydro-1,3,5-trinitro-1,3,5triazine (RDX), but the role of isolates in the degradation process was unknown. Recently, we isolated a facultatively anaerobic bacterium, identified as Klebsiella pneumoniae strain SCZ-1, using MIDI and the 16S rRNA method from this sludge and employed it to degrade RDX. Strain SCZ-1 degraded RDX to formaldehyde (HCHO), methanol (CH 3 OH) (12% of total C), carbon dioxide (CO 2) (72% of total C), and nitrous oxide (N 2 O) (60% of total N) through intermediary formation of methylenedinitramine (O 2 NNHCH 2 NHNO 2). Likewise, hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) was degraded to HCHO, CH 3 OH, and N 2 O (16.5%) with a removal rate (0.39 mol ⅐ h ؊1 ⅐ g [dry weight] of cells ؊1) similar to that of RDX (0.41 mol ⅐ h ؊1 ⅐ g [dry weight] of cells ؊1) (biomass, 0.91 g [dry weight] of cells ⅐ liter ؊1). These findings suggested the possible involvement of a common initial reaction, possibly denitration, followed by ring cleavage and decomposition in water. The trace amounts of MNX detected during RDX degradation and the trace amounts of hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine detected during MNX degradation suggested that another minor degradation pathway was also present that reduced ONO 2 groups to the corresponding ONO groups.
Microbial Degradation and Toxicity of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine
Journal of Microbiology and Biotechnology, 2012
In the present work, current knowledge on the potential fate, microbial degradation, and toxicity of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was thoroughly reviewed, focusing on the toxicological assessment of a variety of potential RDX degradation pathways in bacteria and fungi. The present review on microbial degradation pathways and toxicities of degradation intermediates suggests that, among aerobic RDX degradation pathways, the one via denitration may be preferred in a toxicological perspective, and that among anaerobic pathways, those forming 4nitro-2,4-diazabutanal (NDAB) via ring cleavage of 1-nitroso-3,5-dinitro-1,3,5-triazinane (MNX) may be toxicologically advantageous owing to its potential mineralization under partial or complete anoxic conditions. These findings provide important information on RDX-degrading microbial pathways, toxicologically most suitable to be stimulated in contaminated fields.
Journal of Chromatographic Science, 2004
The use of solid-phase extraction for the analysis of liquid media containing low µg/L levels of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), mononitroso-RDX (MNX), dinitroso-RDX (DNX), and trinitroso-RDX (TNX) is examined. Aqueous samples (100 mL) consisting of water and a microbiological basal medium are spiked with known concentrations of RDX, MNX, DNX, and TNX. The compounds are extracted from the liquid media using a Porapak RDX cartridge and then eluted from the cartridge with 5 mL of acetonitrile. The eluent is concentrated to 1 mL before analysis by high-pressure liquid chromatography (HPLC). The method detection limits for RDX are 0.1 µg/L in water and 0.5 µg/L in the basal medium after a 100-fold concentration. For MNX, DNX, and TNX, the method detection limits are approximately 0.5 µg/L in water and approximately 1 µg/L in the basal medium after a 100-fold concentration. Interferences in the basal medium and a contaminant in the standard made quantitation for MNX and TNX, respectively, is less accurate below the 1 µg/L level. Solid-phase extraction of the liquid media gave good recoveries of nitramines and nitroso intermediates from a microbiological basal medium, allowing HPLC detection of RDX and the nitroso intermediates in the low µg/L (ppb) range.
Applied Microbiology and Biotechnology, 2003
Metabolism of hexahydro-1,3,5-trinitro-1,3,5-triazine through initial reduction to hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine followed by denitration in Clostridium bifermentans HAW-1 Abstract A fast hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)-degrading [28.1 mmol h 1 g (dry weight) cells 1 ; biomass, 0.16 g (dry weight) cells 1 ] and strictly anaerobic bacterial strain, HAW-1, was isolated and identified as Clostridium bifermentans using a 16S-rRNAbased method. Based on initial rates, strain HAW-1 transformed RDX to hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) with yields of 56, 7.3 and 0.2%, respectively. Complete removal of RDX and its nitroso metabolites produced (%, of total C or N) methanol (MeOH, 23%), formaldehyde (HCHO, 7.4%), carbon dioxide (CO 2 , 3.0%) and nitrous oxide (N 2 O, 29.5%) as end products. Under the same conditions, strain HAW-1 transformed MNX separately at a rate of 16.9 mmol h 1 g (dry weight) cells 1 and produced DNX (25%) and TNX (0.4%) as transient products. Final MNX transformation products were (%, of total C or N) MeOH (21%), HCHO (2.9%), and N 2 O (17%). Likewise strain HAW-1 degraded TNX at a rate of 7.5 mmol h 1 g (dry weight) cells 1 to MeOH and HCHO. Furthermore, removal of both RDX and MNX produced nitrite (NO 2 ) as a transient product, but the nitrite release rate from MNX was quicker than from RDX. Thus, the predominant pathway for RDX degradation is based on initial reduction to MNX followed by denitration and decomposition. The continued sequential reduction to DNX and TNX is only a minor route.
2004
In previous work, we studied the anaerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5triazine (RDX) by a methanogenic mixed culture that biodegrades RDX by using H 2 as the sole electron donor. Strain HAAP-1 was isolated after enriching for the homoacetogens in a mineral medium containing RDX and an H 2-CO 2 (80:20) headspace. Strain HAAP-1 degraded 29.0 M RDX in Ͻ14 days and formed 13.0 mM acetate when grown in a mineral medium with an H 2-CO 2 headspace. Methylenedinitramine was observed as a transient intermediate, indicating ring cleavage had occurred. In live cultures containing an N 2-CO 2 headspace, RDX was not degraded, and no acetate was formed. The 16S rRNA gene sequence for strain HAAP-1, consisting of 1485 base pairs, had a 99.2% and 99.1% sequence similarity to Acetobacterium malicum and A. wieringae, respectively. This is the first report of RDX degradation by a homoacetogen growing autotrophically and extends the number of genera known to carry out this transformation.
Water, 2021
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) a nitramine explosive, which has contaminated various military sites during its use, storage and manufacturing worldwide. As RDX is a recalcitrant, less soluble and toxic to human beings and other organisms, it is essential to remediate the contaminated sites. In the current investigation, authors have explored the potential of two indigenous microbes i.e., Bacillus toyonensis (isolate No. WS4-TSB-3, MTCC No. 12857) and Paenibacillus dendritiformis (isolate No. S10-TSA-3, MTCC No. 12859) isolated from an explosive manufacturing facility in north India, for the degradation of RDX in aqueous medium. Furthermore, RDX degradation has been optimized using response surface methodology (RSM) in a 15 days experiment at concentration of 20, 40, and 60 mg/L. It was found that various factors such as initial concentration of RDX, inoculum volume (2, 4 and 6%) and time (5, 10 and 15 days) had impact on transformation and degradation of contaminant. ...
Applied and Environmental Microbiology, 2016
ABSTRACTKinetic isotopic fractionation of carbon and nitrogen during RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) biodegradation was investigated with pure bacterial cultures under aerobic and anaerobic conditions. Relatively large bulk enrichments in15N were observed during biodegradation of RDX via anaerobic ring cleavage (ε15N = −12.7‰ ± 0.8‰) and anaerobic nitro reduction (ε15N = −9.9‰ ± 0.7‰), in comparison to smaller effects during biodegradation via aerobic denitration (ε15N = −2.4‰ ± 0.2‰).13C enrichment was negligible during aerobic RDX biodegradation (ε13C = −0.8‰ ± 0.5‰) but larger during anaerobic degradation (ε13C = −4.0‰ ± 0.8‰), with modest variability among genera. Dual-isotope ε13C/ε15N analyses indicated that the three biodegradation pathways could be distinguished isotopically from each other and from abiotic degradation mechanisms. Compared to the initial RDX bulk δ15N value of +9‰, δ15N values of the NO2−released from RDX ranged from −7‰ to +2‰ during aerobic b...
Applied and Environmental Microbiology, 2002
indicating that two of the three N atoms in the metabolite originated from the ring in RDX. When [U-14 C]-RDX was used in the experiment, 64% of the original radioactivity in RDX incorporated into the metabolite with a molecular weight (MW) of 119 (high-pressure LC/radioactivity) and 30% in 14 CO 2 (mineralization) after 4 days of incubation, suggesting that one of the carbon atoms in RDX was converted to CO 2 and the other two were incorporated in the ring cleavage product with an MW of 119. Based on the above stoichiometry, we propose a degradation pathway for RDX based on initial denitration followed by ring cleavage to formaldehyde and the dead end product with an MW of 119. This is NRCC publication number 44634.
Bioremediation Journal, 2000
Microcosm tests simulating bioslurry reactors with 40% soil content, containing high concentrations of TNT and/or RDX, and spiked with either [ 14 C]-TNT or [ 14 C]-RDX were conducted to investigate the fate of explosives and their metabolites in bioslurry treatment processes. RDX is recalcitrant to indigenous microorganisms in soil and activated sludge under aerobic conditions. However, soil indigenous microorganisms alone were able to mineralize 15% of RDX to CO 2 under anaerobic condition, and supplementation of municipal anaerobic sludge as an exogenous source of microorganisms significantly enhanced the RDX mineralization to 60%. RDX mineralizing activity of microorganisms in soil and sludge was significantly inhibited by the presence of TNT. TNT mineralization was poor (< 2%) and was not markedly improved by the supplement of aerobic or anaerobic sludge. Partitioning studies of [ 14 C]-TNT in the microcosms revealed that the removal of TNT during the bioslurry process was due mainly to the transformation of TNT and irreversible binding of TNT metabolites onto soil matrix. In the case of RDX under anaerobic conditions, a significant portion (35%) of original radioactivity was also incorporated into the biomass and bound to the soil matrix.