Denitration of 2,4,6-Trinitrotoluene in Aqueous Solutions Using Small-Molecular-Weight Catalyst(s) Secreted by Pseudomonas aeruginosa ESA-5

Abstract

The denitration of 2,4,6-trinitrotoluene (TNT) can produce mono- or dinitro aromatic compounds susceptible to microbial mineralization. In the present study, denitration of TNT and other nitro aromatic compounds was investigated with a solid-phase extract obtained from the culture supernatant of Pseudomonas aeruginosa ESA-5 grown on a chemically defined aerobic medium. When the C18 solid-phase extract containing extracellular catalysts (EC) was incubated with TNT and NAD(P)H, we observed a significant release of nitrite. The concentration of nitrite released in the reaction medium was strongly dependent on the concentration of NAD(P)H and EC. Denitration also occurred with two TNT-related molecules, 2,4,6-trinitrobenzaldehyde, and 2,4,6-trinitrobenzyl alcohol. The release of nitrite was coupled with the formation of two polar metabolites, and mass spectrometry analyses indicated that each of these compounds had lost two nitro groups from the trinitro aromatic parent molecule. During this process, the production of toxic reduced TNT metabolites was minimal. The incubation of EC with TNT, NAD(P)H, and specific scavengers of reactive oxygen species suggested the involvement of superoxide radicals (O2*-) and hydrogen peroxide in the denitration process. Results obtained in this study reveal for the first time that extracellular small-molecular-weight substance(s) of bacterial origin can serve as green catalyst(s) to initiate TNT denitration. In addition, this study gives clear evidence for the production of a TNT metabolite bearing a single nitro groupfollowing a denitration reaction with catalyst(s) of biotic origin.

Acetate production from inorganic carbon (HCO3-) in photo-assisted biocathode microbial electrosynthesis systems using WO3/MoO3/g-C3N4 heterojunctions and Serratia marcescens species

“…However, its concentration of 0.72 μM in this assembling system (Fig. S10B) was lower than the harmful onset value to Pseudomonas aeruginosa of 3.0 μM [58], excluding its detrimental effect on the S. marcescens, consistent with the results in Fig. S7.…”

“…The extreme anaerobic conditions purposely controlled throughout this study excluded the generation of potentially harmful reactive oxygen species [9][10][11] and the deleterious effect on the CEacetate. In parallel, the very small amount of •OH quantitatively probed using p-hydroxybenzoic acid [58] and the negligible change in the electrotrophic viability using high-sensitivity flow cytometry, collectively excluded the detrimental effect of the radicals on the reproduction and sustainability of the S. marcescens biofilm, in the presence of the photocatalyst and under light irradiation conditions. With regard to the change of the cathodic biofilms thickness with operational time, electrotrophs were generally sparsely distributed on the cathodes, which contrasted with the dense biofilms on the anodes [59].…”

Efficient production of acetate from inorganic carbon (HCO3–) in microbial electrosynthesis systems incorporating Ag3PO4/g-C3N4 anaerobic photo-assisted biocathodes

“…Quantification of the hydroxyl radicals by HPLC (0.8 μM) (Fig. S8) confirmed a significantly lower concentration than the harmful onset value reported for Pseudomonas aeruginosa of 3.0 μM [47], implying negligible impact of the hydroxyl radicals on the viability of S. marcescens. Moreover, the highest concentration of H2O2 produced in-situ (OCCs, 144 ± 3 μM, Fig.…”

Uncovering the Structure and Function of Microbial Communities Formed During Periodic Tilling of TNT and DNT Co-Contaminated Soils

“…Although MNT and DNT compounds can be oxidatively cleaved, the symmetrical arrangement of nitro groups on TNT makes the aromatic ring electron-deficient and electrophilic, which in turn prevents oxidative attacks of TNT using electrophilic-driven oxidation by oxygenases. This arrangement favors reductive, nucleophilic transformation mechanisms (Stenuit, Eyers et al 2009), under both aerobic and anaerobic conditions. There…”