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2 Central European Journal of Energetic Materials

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Mineralization and Uptake of TNT by Microorganisms: Effect of Pretreatment with Alkali

Herrmann S., Popović M. K., Paca J., Halecky M., Bajpai R. K.

Central European Journal of Energetic Materials

2007

Vol. 4, nr 4

45-58

Four bacterial strains capable of growing on nitrotoluenes were incubated in basal salt medium containing either 2,4,6-trinitrotoluene (TNT) or its alkali hydrolysate (starting pH 12; duration 24 h) as carbon sources. The bacterial strains were identified as Burkholderia cepacia SH-1, Pseudomonas aeruginosa SH-2, Pseudomonas putida MC-I, and Pseudomonas sp. X. Burkholderia cepacia SH-1 was able to grow in medium containing TNT as the sole carbon source and it transformed approximately 80% TNT into metabolic products within six days. Addition of glucose or succinate improved both the growth of cells and TNT uptake. When supplemented with glucose, the Pseudomonas strains achieved significantly higher medium optical density as well as TNT transformation. The Pseudomonas aeruginosa SH-2 cells were most active in transforming TNT. Optical densities of all the cultures were higher after incubation with TNT-hydrolysate when compared to TNT only. In experiments with uniformly labeled 14C-TNT and Burkholderia cepacia SH-1, the distribution of radioactivity was 0.15% in CO2 produced, 4.88% in cell mass, 71.9% in solution, and 23% unaccounted. The same distribution when strain SH-1 was incubated in alkali hydrolysate of TNT, was 0.44% 14CO2, 6.9% in cell mass, 22.5% in aqueous solution, and 70% unaccounted for.

Effect of Nitrate on Biodegradation of Mononitrotoluenes (MNTs) by Several Pure Microbial Strains in Submerged Aerobic Cultures

Paca J., Halecky M., Barta J., Paca J. Jr., Stiborova M., Bajpai R

Central European Journal of Energetic Materials

2006

Vol. 3, nr 3

65-78

Four microbial strains, isolated from a mixed culture, were used to study biodegradation of 2-nitrotoluene, 3-nitrotoluene, and 4-nitrotoluene individually and in a mixture. The strains were identified as Pseudomonas putida S7, Comamonas testosteroni Pb 50, Rhodococcus sp. Pa 50, and Stenotrophomonas malthophilia K3. The degradation studies were carried out with suspended cells in aqueous media under aerobic conditions and the results were compared with new extensive studies on biodegradation of mononitrotoluenes with a mixed culture isolated from explosives’ contaminated soil from another site. The results showed that (a) the degradation rate of MNTs by the individual strains were of the same order of magnitude as that by the Pardubice mixed culture, (b) the 66 J. Paca, M. Halecky et al. presence of additional N-source positively affected the degradation rate for 3-NT and 4-NT, but adversely affected the degradation rate of 2-NT, (c) no incompletely oxidized dead-end intermediates were found under aerobic conditions, (d) all the cell lines were able to efficiently degrade all the MNTs, even when all were present together, and (e) the degradation rates of individual MNTs in a mixture were slightly lower than when just one NT was present. Substrate concentration affected degradation rates according to classical substrate inhibition.