Dr. Noguera et Dl. Freedman, CHARACTERIZATION OF PRODUCTS FROM THE BIOTRANSFORMATION OF 2,4-DINITROTOLUENE BY DENITRIFYING ENRICHMENT CULTURES, Water environment research, 69(3), 1997, pp. 260-268
Anoxic biotransformation of 2,4-dinitrotoluene (DNT) was examined and
two denitrifying enrichment cultures were developed. In one, the inocu
lum was acclimated to treatment of munitions wastewater that contains
DNT; the other was derived from activated sludge that was not routinel
y exposed to nitroaromatics. DNT was consumed readily by both cultures
only when ethanol was provided as a primary substrate, with the rate
of transformation twice as fast in the acclimated culture. [C-14]DNT w
as used to track the metabolites. A negligible amount of the DNT was m
ineralized. The principal initial biotransformation pathway was reduct
ion of DNT to aminonitrotoluenes. Subsequent transformations in the ac
climated culture resulted in formation of 6-nitroindazole, 2-nitrotolu
ene, and 4-nitrotoluene, which have not previously been reported as me
tabolites from DNT. Acetylation at the para position was another impor
tant transformation pathway in the acclimated culture, resulting in ac
cumulation of 4-acetamide-2-nitrotoluene and 4-acetamidetoluene. Reduc
tion of aminonitrotoluenes to 2,4-diaminotoluene also occurred, follow
ed by conversion of approximately one-third of the C-14 activity to no
nfilterable material. The majority of the soluble DNT metabolites from
the unacclimated culture were hydrophilic; these were characterized b
y gradient elution high-pressure liquid chromatography analysis and io
n pairing chromatography as approximately equal amounts of negatively
charged and neutral compounds. The diversity and characteristics of th
ese metabolites indicates that biotransformation of DNT under anoxic c
onditions does not necessarily eliminate the toxicological hazards ass
ociated with the parent compound. Metabolite formation should be taken
into consideration when determining discharge criteria for DNT-contam
inated wastewaters exposed to denitrifying environments.