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Biotransformation of 2,4,6–trinitrotoluene in Anabaena sp. cultures
Author(s) -
Pavlostathis Spyros G.,
Jackson Gardner H.
Publication year - 1999
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620180307
Subject(s) - trinitrotoluene , biotransformation , anabaena , azoxy , aeration , chemistry , transformation (genetics) , incubation , chromatography , cyanobacteria , environmental chemistry , nuclear chemistry , biology , biochemistry , organic chemistry , bacteria , enzyme , gene , genetics , explosive material
The transformation of 2,4,6‐trinitrotoluene (TNT) was investigated in cultures of the cyanobacterium Anabaena sp. by conducting a series of batch assays. 2,4,6‐Trinitrotoluene was added to Anabaena sp. cultures in single and consecutive additions, at various initial concentrations, to determine its transformation kinetics, to identify products formed, to evaluate potential toxicity, and to determine the effect of light deprivation on the TNT transformation process. 2,4,6‐Trinitrotoluene disappearance occurred only in the presence of Anabaena sp. cultures maintained under a normal 16‐h photoperiod. Toxicity leading to culture chlorosis and death was observed in batch systems with an initial TNT concentration greater than 10 mg/L. A low rate and extent of TNT disappearance was observed in light‐deprived cultures, which were inhibited even at low TNT concentrations (i.e., <4 mg/L). At pH values between 7.5 and 8.5, azoxy‐tetranitrotoluene isomers were detected in both the culture medium and solvent extracts of biomass and accounted for only 20 and 4.4% of the initially added TNT moles, respectively. At a culture pH range between 5.6 and 5.9, achieved by aeration with a 5% CO 2 /air mixture, hydroxylaminodinitrotoluene equimolar to the TNT addition was produced and then depleted from the culture medium with prolonged incubation. Although TNT reduction in Anabaena sp. cultures occurred, yielding low levels of azoxy‐tetranitrotoluene isomers or hydroxylaminodinitrotoluene (depending on the culture pH conditions), uptake and other transformation reactions of TNT and/or its transformation products by Anabaena sp. may have taken place. Based on a less than 15% observed increase of biomass concentration over the relatively short incubation periods (usually <6 h) and by considering the mean biomass concentration constant, the TNT disappearance rate followed pseudo‐first‐order kinetics. The biomass carbon‐normalized TNT disappearance rates in Anabaena sp. cultures were about three orders of magnitude higher than previously reported TNT disappearance rates obtained in batch cultures of aquatic plants.