Nitroglycerin (glycerol trinitrate [GTN]), an explosive and vasodilatory compound, was metabolized by mixed microbial cultures from aeration tank sludge previously exposed to GTN. Aerobic enrichment cultures removed GTN rapidly in the absence of a supplemental carbon source. Complete denitration of GTN, provided as the sole C and N source, was observed in aerobic batch cultures and proceeded stepwise via the dinitrate and mononitrate isomers, with successive steps occurring at lower rates. The denitration of all glycerol nitrate esters was found to be concomitant, and 1,2-glycerol dinitrate (1,2-GDN) and 2-glycerol mononitrate (2-GMN) were the primary GDN and GMN isomers observed. Denitration of GTN resulted in release of primarily nitrite-N, indicating a reductive denitration mechanism. Biomass growth at the expense of GTN was verified by optical density and plate count measurements. The kinetics of GTN biotransformation were 10-fold faster than reported for complete GTN denitration under anaerobic conditions. A maximum specific growth rate of 0.048 ± 0.005 h−1 (mean ± standard deviation) was estimated for the mixed culture at 25°C. Evidence of GTN toxicity was observed at GTN concentrations above 0.3 mM. To our knowledge, this is the first report of complete denitration of GTN used as a primary growth substrate by a bacterial culture under aerobic conditions.

Biological treatment of nitroglycerin (glycerol trinitrate [GTN]) by a mixed microbial culture was examined under aerobic conditions in a bench-scale sequencing batch reactor with GTN present as a minor component in the feed. Initial operation demonstrated the resistance of GTN and glycerol dinitrates (GDNs) to microbial attack. The presence of GTN and GDNs adversely affected microbial activity, reflected by erratic mixed liquor suspended solids concentrations and low chemical oxygen demand removal efficiencies. Complete removal of GTN and GDNs was contingent on addition of a GTN-adapted inoculum. Transient accumulation and subsequent removal of 1,2-GDN, 1,3-GDN, and nitrite were measured during individual reaction cycles. Complete mineralization of GTN was confirmed and GDN denitration was the rate limiting step governing GTN mineralization. Water Environ. Res., 72, 499 (2000).

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