Evaluating the comparative potential of two indigenous microbial strains for degradation of 2,4,6- trinitrotoluene (TNT) and their biotransformation mechanisms

Abstract. 2,4,6-Trinitrotoluene (TNT) is a high energetic explosive compound with widespread military and civil applications. Its inadequate management and handling during manufacturing, transportation, exercising, demilitarization and detonation practices often lead to contamination of environmental matrices like soil and water. Environmental Protection Agency (EPA, 2014) has categorized TNT as a group C carcinogen, and a high toxic explosive which may lead to detrimental health effects, including anemia, cataracts, liver damages, and reproductive and immune system impairments. EPA has recommended a lifetime health advisory guidance level for TNT in drinking water as 2μg/L and set soil screening level of 19mg/Kg in residential and 79mg/Kg in industrial soil. Therefore, it is crucial to mitigate the negative impacts and possible associated risks to protect the environment. Microbial remediation can be an effective and sustainable option for clean-up of explosive contaminated sites as it promotes both environmental and economical aspects and has a lot of public acceptance. The current study was carried out with an objective to evaluate the potential of two indigenous microbial strains, Paenibacillus dendritiformis and Arthrobacter subterraneus which were isolated from an actual contaminated site for the degradation of TNT. The experimental studies involved assessing their ability to uptake the explosive as carbon and nitrogen source in controlled conditions in aqueous medium. A 30-days shake flask experiment was conducted under varying concentrations of TNT i.e. 60, 80, 100, and 120 mg/L. The reduction in concentration and biotransformation in secondary metabolites were obtained using high end instruments like High Performance Liquid Chromatography (HPLC) and Liquid Chromatography Mass Spectroscopy (LC-MS/MS). A degradation of 52 to 92% was achieved by Paenibacillus dendritiformis whereas, 52-65% was achieved by Arthrobacter subterraneus at different concentrations. Results confirmed the Paenibacillus sp. as better performer in degradation of TNT revealing its potential to remediate the explosive contaminated sites through microbial remediation technology.