Browsing by Subject "TNT (Chemical)--Toxicology."
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Item Open Access Bioremediation of 2,4,6-Trinitrotoluene by novel strains of aerobic bacteria(Bilkent University, 2012) Gümüşcü, Burcu2,4,6-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.Item Open Access Novel biological materials for food and environmental applications(Bilkent University, 2012) Umu, Özgün Candan OnarmanProbiotics are microorganisms that have many health benefits to their host, such as promoting normal intestinal microflora, inhibiting the growth of pathogenic microorganisms, improving digestion and stimulation of gastrointestinal immunity. Probiotic microorganisms include bacteria, fungi and yeast, and they are highly desirable to be used as animal feed supplements. For this application, Bacillus species are preferred since they are resistant to extreme environmental conditions due to their spore-forming capacity in addition to having other important probiotic characteristics. In the first chapter of this study, 84 independent bacterial colonies were obtained from different bovine chyme samples and among them 29 were determined as belonging to genus Bacillus. These isolates were principally screened for their antimicrobial activity against a group of selected bacteria including pathogenic organisms such as Salmonella enterica, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. 7 strains (STF4, STF8, STF9, STF10, STF15, STF25 and STF26) with highest antimicrobial activity were further tested for other probiotic properties. They were resistant to the gastrointestinal conditions and most of the antibiotics tested. In addition, they were checked for the presence of plasmids and performed cytotoxicity tests. We propose novel Bacillus strains that have potential to be used as probiotic organisms. TNT is a hazardous nitroaromatic compound that can be found in soil, sediment and water due to extensive contamination from military munitions after the World War II. It has many negative health effects on almost all of the living organisms (e.g. bacteria, fungi, algae, animal and human). So far, bacteria, fungi and plants are commonly used for biodegradation process but only a little is known about effect of algae on this issue. However, algae can be used as a good alternative for bioremediation and biosensor purposes as they do not require advance technology and are effective in terms of cost. 5 different microalgae strains (STA1, STA2, STA3, STA4 and STA5) were tested in terms of survival in different TNT concentration and biodegradation capability of TNT. These strains were isolated from water contaminated with TNT obtained from the Brass Factory affiliated with Mechanical and Chemical Industry Corporation (MKE) located in Kırıkkale, Turkey. Even though these strains did not use TNT as carbon source for growth; they utilize it at different degrees for other metabolic activities. Moreover, the growth of STA2 strain was not inhibited by high TNT concentrations (up to 50 mg/L TNT).