Biotransformation Routes of Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine by Municipal Anaerobic Sludge

Abstract

Recently we demonstrated that hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), a trimer of methylene nitramine (CH2=N-NO2) undergoes spontaneous decomposition following an initial microbial attack using a mixed microbial culture at pH 7 in the presence of glucose as carbon source. The present study describes whether the second cyclic nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), a more strained tetramer of CH2=N-NO2, degrades similarly using sludge of the same source. Part of HMX biotransformed to give products that are tentatively identified as the nitroso derivatives octahydro-1-nitroso-3,5,7-trinitro-1,3,5,7-tetrazocine (mNs-HMX) and octahydro-1,3-dinitroso-5,7-dinitro-1,3,5,7-tetrazocine and its isomer octahydro-1,5-dinitroso-3,7-dinitro-1,3,5,7-tetrazocine (dNs-HMX). Another fraction of HMX biotransformed, apparently via ring cleavage, to produce products that are tentatively identified as methylenedinitramine (O2NNHCH2-NHNO2) and bis(hydroxymethyl)nitramine ((HOCH2)2NNO2). None of the above intermediates accumulated indefinitely; they disappeared to predominantly form nitrous oxide (N2O) and formaldehyde (HCHO). Formaldehyde biotransformed further to eventually produce carbon dioxide (14CO2). Nitrous oxide persisted in HMX microcosms containing glucose but denitrified rapidly to nitrogen in the absence of glucose. The presence of nitrous oxide was accompanied by the presence of appreciable amounts of hydrogen sulfide, a known inhibitor of denitrification.

Biodegradation of the nitramine explosives hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine in cold marine sediment under anaerobic and oligotrophic conditions

“…The RDX and HMX in the aqueous phase were monitored over a period of 4 months. RDX, HMX, and their products were analyzed by previously described methods (Hawari et al , 2001 Figure 1A shows the anaerobic removal of RDX (0.59 mg) in the presence of HMX (0.048 mg) in the marine sediment suspension at 10°C. The concentration of RDX in the aqueous phase decreased to half after 4 days of incubation and disappeared from the aqueous phase with or without supplementation of carbon sources after 35 days of incubation.…”

“…Bacteria in soil (Young et al 1997a(Young et al , 1997b, anaerobic sludge (McCormick et al 1981;Hawari et al 2000Hawari et al , 2001Hawari et al , 2002Zhao et al 2002Zhao et al , 2003aZhao et al , 2003b, fresh water sediments (Beller 2002;Boopathy et al 1998), and horse manure (Kitts et al 1994) were reported to degrade RDX and HMX under oxygen-limited conditions. We found that bacteria from anaerobic sludge could degrade RDX and HMX to nitrous oxide (N 2 O) and formaldehyde via initial denitration (Hawari et al , 2001Halasz et al 2002;Zhao et al 2002Zhao et al , 2003aZhao et al , 2003b.…”

“…We found that bacteria from anaerobic sludge could degrade RDX and HMX to nitrous oxide (N 2 O) and formaldehyde via initial denitration (Hawari et al , 2001Halasz et al 2002;Zhao et al 2002Zhao et al , 2003aZhao et al , 2003b. Little data are currently available on the fate and degradation of explosives from UXO in marine sediments.…”

Protocol for Enhanced in situ Bioremediation Using Emulsified Edible Oil

“…Metabolites containing nitroso groups may then sorb to organic material while metabolites containing aromatic hydroxylamine and amine groups can form irreversible covalent bonds with humics immobilizing these materials (Achtnich et al, 1999;Thorn and Kennedy, 2002). Under anaerobic conditions, the RDX and HMX ring may be cleaved resulting in complete mineralization (Hawari et al, 2000(Hawari et al, , 2001 or the nitro groups in RDX and HMX may be reduced to nitroso groups (Price et al, 2001;Beller, 2002).…”

Quinone- and nitroreductase reactions of Thermotoga maritima peroxiredoxin–nitroreductase hybrid enzyme

“…The reduction of quinones and nitroaromat-28 ics by NR proceeded in a two-electron manner, and follows a 'ping-pong' scheme with sometimes pro-29 nounced inhibition by quinone substrate. The comparison of steady-and presteady-state kinetic data 30 shows that in most cases, the oxidative half-reaction may be rate-limiting in the catalytic cycle of NR. …”