Complete denitration of nitroglycerin by bacteria isolated from a washwater soakaway

Four axenic bacterial species capable of biodegrading nitroglycerin (glycerol trinitrate [GTN]) were isolated from soil samples taken from a washwater soakaway at a disused GTN manufacturing plant. The isolates were identified by 16S rRNA gene sequence homology as Pseudomonas putida, an Arthrobacter species, a Klebsiella species, and a Rhodococcus species. Each of the isolates utilized GTN as its sole nitrogen source and removed nitro groups sequentially from GTN to produce glycerol dinitrates and mononitrates (GMN), with the exception of the Arthrobacter strain, which achieved removal of only the first nitro group within the time course of the experiment. The Klebsiella strain exhibited a distinct preference for removal of the central nitro group from GTN, while the other five strains exhibited no such regioselectivity. All strains which removed a second nitro group from glycerol 1,2-dinitrate showed regiospecific removal of the end nitro group, thereby producing glycerol 2-mononitrate. Most significant was the finding that the Rhodococcus species was capable of removing the final nitro group from GMN and thus achieved complete biodegradation of GTN. Such complete denitration of GTN has previously been shown only in mixed bacterial populations and in cultures of Penicillium corylophilum Dierckx supplemented with an additional carbon and nitrogen source. Hence, to the best of our knowledge, this is the first report of a microorganism that can achieve complete denitration of GTN.