Browsing by Subject "biodegradation"

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Open Access
Bioremediation of 2,4,6-Trinitrotoluene by novel strains of aerobic bacteria
(2012) Gümüşcü, Burcu
2,4,6-Trinitrotoluene (TNT) has been used extensively for military purposes since its invention in the late 19th century. TNT is a highly toxic and recalcitrant substance due to its multiple nitrated molecular configuration. TNT residues can enter biological systems and constitute a significant risk to human health. To this end, biological approaches promise great potential for removal of TNT in both aqueous and terrestrial environments by the usage of microorganisms. However, remediation capabilities of these organisms are limited due to their inadequate survival and degradation capacity in the environment. To address these issues, we investigated and demonstrated high degradation performance of novel bacterial strains isolated from TNT-contaminated sites, Citrobacter murliniae STE 10, Achromobacter spanius STE 11, Kluyvera cryocrescens STE 12, and Enterobacter amnigenus STE 13, for an enhanced remediation process. In the first part of this thesis, we developed a novel HPLC method on a Diol-functionalized chromatography column for accurate, rapid, economic, and environmentally friendly detection of nitroaromatic compounds. Data obtained from chromatography measurements clearly verified that the minimum limit of detection values for TNT and TNT metabolites (0.78-1.17 µg/L) were lower than the values obtained by previous reports and the widely used EPA method. In the second part, for the first time, we achieved rapid (less than 20 h) TNT decontamination using novel bacterial strains under aerobic conditions at 99.9% efficiency. We showed that TNT was transformed into less toxic and highly reactive metabolites. The data obtained from elemental analysis and HPLC measurements together with FT-IR results indicated that approximately 71.42% of nitrogen from TNT is accumulated in the biomass. In the third part, we designed laboratory-scale compost system for optimization of maximum TNT degradation efficiency. In this study, we observed a strong correlation between degradation capacity of microorganisms and carbon/nitrogen (C/N) ratio, air flow, and TNT amounts. We accomplished a complete TNT degradation (100%) by an in-vessel compost system in 15 days, the shortest period ever reported. These bioremediation approaches hold great promise for efficient and sustainable removal of TNT for safe environment.
Open Access
Effective biodegradation of 2,4,6-trinitrotoluene using a novel bacterial strain isolated from TNT-contaminated soil
(2013) Gumuscu, B.; Tekinay, T.
In this environmental-sample based study, rapid microbial-mediated degradation of 2,4,6-trinitrotoluene (TNT) contaminated soils is demonstrated by a novel strain, Achromobacter spanius STE 11. Complete removal of 100mgL-1 TNT is achieved within only 20h under aerobic conditions by the isolate. In thisbio-conversion process, TNT is transformed to 2,4-dinitrotoluene (7mgL-1), 2,6-dinitrotoluene (3mgL-1), 4-aminodinitrotoluene (49mgL-1) and 2-aminodinitrotoluene (16mgL-1) as the key metabolites. A. spanius STE 11 has the ability to denitrate TNT in aerobic conditions as suggested by the dinitrotoluene and NO3 productions during the growth period. Elemental analysis results indicate that 24.77mgL-1 nitrogen from TNT was accumulated in the cell biomass, showing that STE 11 can use TNT as its sole nitrogen source. TNT degradation was observed between pH 4.0-8.0 and 4-43°C; however, the most efficient degradation was at pH 6.0-7.0 and 30°C. © 2013 Elsevier Ltd.