Aerobic denitration of 2,4,6-trinitrotoluene in the presence of phenazine compounds and reduced pyridine nucleotides

Environ Sci Technol. 2012 Oct 2;46(19):10605-13. doi: 10.1021/es302046h. Epub 2012 Sep 10.

Abstract

Phenazine-containing spent culture supernatants of Pseudomonas aeruginosa concentrated with a C18 solid-phase extraction cartridge initiate NAD(P)H-dependent denitration of 2,4,6-trinitrotoluene (TNT). In this study, TNT denitration was investigated under aerobic conditions using two phenazine secondary metabolites excreted by P. aeruginosa, pyocyanin (Py) and its precursor phenazine-1- carboxylic acid (PCA), and two chemically synthesized pyocyanin analogs, phenazine methosulfate (PMS+) and phenazine ethosulfate (PES+). The biomimetic Py/NAD(P)H/O2 system was characterized and found to extensively denitrate TNT in unbuffered aqueous solution with minor production of toxic amino aromatic derivatives. To a much lesser extent, TNT denitration was also observed with PMS+ and PES+ in the presence of NAD(P)H. No TNT denitration was detected with the biomimetic PCA/NAD(P)H/O2 system. Electron paramagnetic resonance (EPR) spectroscopy analysis of the biomimetic Py/NAD(P)H/O2 system revealed the generation of superoxide radical anions (O2 •−). In vitro TNT degradation experiments in the presence of specific inhibitors of reactive oxygen species suggest a nucleophilic attack of superoxide radical anion followed by TNT denitration through an as yet unknown mechanism. The results of this research confirm the high functional versatility of the redox-active metabolite pyocyanin and the susceptibility of aromatic compounds bearing electron withdrawing substituents, such as nitro groups, to superoxide-driven nucleophilic attack.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aerobiosis
  • Catalysis
  • Culture Media
  • Electron Spin Resonance Spectroscopy
  • Methylphenazonium Methosulfate / chemistry
  • Methylphenazonium Methosulfate / metabolism
  • NADP / chemistry
  • NADP / metabolism*
  • Phenazines / chemistry
  • Phenazines / metabolism
  • Pseudomonas aeruginosa / chemistry
  • Pseudomonas aeruginosa / metabolism*
  • Pyocyanine / metabolism
  • Reactive Oxygen Species / metabolism
  • Solid Phase Extraction
  • Superoxides / metabolism
  • Trinitrotoluene / chemistry*
  • Trinitrotoluene / metabolism*

Substances

  • Culture Media
  • Phenazines
  • Reactive Oxygen Species
  • 5-ethylphenazine
  • Superoxides
  • Trinitrotoluene
  • 1-phenazinecarboxylic acid
  • Methylphenazonium Methosulfate
  • NADP
  • Pyocyanine