Reducing one of the nitro groups on TNT (2,4,6-trinitrotoluene) to an amine could render the explosive much easier to bioremediate with a bacterial oxygenase, report Jim Spain and researchers at the U.S Air Force Research Laboratory and the University of Connecticut. They describe a scheme in which an amino form of TNT can continue decomposition through an oxidation pathway.

Currently, incineration is the best method to remove toxic and explosive TNT from contaminated sites, but the approach is expensive and causes air pollution. Bioremediation would be an attractive alternative, but it appears that bacterial oxygenase enzymes cannot attack TNT directly. Spain and his colleagues speculated that the problem is that the nitro substituents in TNT withdraw too much electron density from the ring, inhibiting efficient enzymatic attack on the molecule.

Using a bacterial reductase, the researchers generated aminodinitrotoluene (ADNT) isomers, a typical breakdown product which is known to have more electron density than TNT. According to a rate study, ADNT is a much more likely substrate for nitroarene dioxygenase attack. These findings expand the nitroarene dioxygenases’ capability beyond known substrates like mono- and di-nitrotoluenes and exhibit potential for better TNT remediation. (Appl. Environ. Microbiol. 2001, 67, 5460–5466) —RACHEL PETKEWICH