Biotransformation of 2,4,6-Trinitrotoluene in Anabaena Sp. Cultures

Abstract

Abstract-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., Ͻ4 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 Ͻ6 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.

Mineralization of 2,4,6-Trinitrotoleune (TNT) in Coastal Waters and Sediments

“…This was compared to rates about 30-fold lower for the bacteria only culture media. The difference between the two treatments was attributed to uptake by Anabaena alone (Pavlostathis and Jackson 2002) though it should be noted that if there was enhanced removal by bacteria in the presence of Anabaena, this removal would have been attributed to Anabaena by these researchers. These works highlight the possible use of marine cyanobacteria for TNT remediation.…”

“…50 mg TNT L -1 d -1 ) and metabolized N from TNT (Pavlostathis and Jackson 2002). This was compared to rates about 30-fold lower for the bacteria only culture media.…”

“…This aspect of cycling and fate of TNT is particularly relevant because nitrogen (N), a key component of energetic compounds, frequently controls the rate of primary production in marine, estuarine and some freshwater ecosystems (Sharp 1991). Most work on TNT and microalgae has described the toxic effects of the energetic (Smock et al 1976, Won et al 1976, Burton et al 1994, Tandros et al 2000 though many of these effects can be reversed if the algae are maintained in flow through systems (Pavlostathis and Jackson 2002). There are some reports on uptake and metabolism of TNT by microalgae (Mondecar et al 1994, Pavlostathis and Jackson 1999 as a potential environmental cleanup strategy.…”

Biotransformation of Aldrin and Chlorpyrifos-methyl by Anabaena sp. PCC 7120

“…Anabaena sp. can transform 2,4,6-trinitrotoluene (TNT) to azoxy-tetranitrotoluene and hydroxyaminodinitrotoluene (Pavlostathis and Jackson, 1999). In this study, we report that Anabaena sp.…”

Federal Integrated Biotreatment Research Consortium (FIBRC): Flask to Field Initiative

“…3). 4HADNT, the first product to appear, is converted directly to 4ADNT in a number of bacterial, plant and fungal systems (Hawaii et al, 1999;Khan et al, 1997;Michels and Gottschalk, 1994;Pavlostathis and Jackson, 1999;Van Aken et al, 1997), but in the JS45 system a second partial reduction yielded 2,4-dihydroxylamino-6-nitrotoluene (DHANT). Experiments with purified nitrobenzene nitroreductase made it clear that the nitrobenzene nitroreductase catalyzed the reactions and was unable to reduce the hydroxylamino groups to amines.…”