Biotransformation of Trinitrotoluene (TNT) by Newly Isolated Slight Halophilic Bacteria
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XPERIMENTAL ARTICLES
Biotransformation of Trinitrotoluene (TNT) by Newly Isolated Slight Halophilic Bacteria M. Ali-Beglouia, E. Salehghamarib, *, S. Sadraic, M. Ebrahimia, M. A. Amoozegara, and A. Salehi-Najafabadia a
Department of Microbiology, School of Biology, University College of Science, University of Tehran, Tehran, Iran bDepartment of Cell and Molecular Science, School of Biological Science, Kharazmi University, Tehran, Iran cPharmaceutics Department, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran *e-mail: [email protected] Received November 23, 2019; revised December 26, 2019; accepted April 26, 2020
Abstract—Current study reports isolation of newly isolated slight halophilic bacteria which can utilize 2,4,6trinitrotoluene (TNT) as a sole nitrogen source, leading to its detoxification. Among 100 halo(alkali)tolerant and halo(alkali)philic strains were isolated from TNT-contaminated soil, two slight halophilic alkalitolerant strains showed remarkable ability to quickly remove the different concentrations of TNT up to 200 mg/L during 24 h in aerobic condition. Phylogenetic analysis indicates that both strains belonged to the genus Pseudomonas which were able to grow aerobically in different concentrations of NaCl (up to 5 and 10%, respectively), temperature (25–40°C), and pH (7–9). Kinetic studies of TNT biotransformation process showed this growth-associated process followed the first-order expression with parameters of kd: 0.09–0.11 mg/(L h), Т1/2: 6–7 h, μ: 0.17–0.25 1/h leading to a removal of 90% of TNT (100 mg/L) during a 24 hour period. Finally, the growth rate of both strains evaluated on minimal and complex media, and growth parameters were optimized for maximum growth and most likely maximum biotransformation. Keywords: biotransformation, halophilic bacteria, 2,4,6-trinitrotoluene, kinetics DOI: 10.1134/S0026261720050033
Nitroaromatics form a major class of xenobiotic compounds. They are widely used as pesticides, dyes, polymer additives, explosives and plastics (Kulkarni and Chaudhari, 2006). During both world wars, some of these compounds such as 2,4,6-trinitrotoluene (TNT) were developed and produced on a heavy scale for military and civilian purposes. As a result, high concentration of TNT was spread in soil and groundwater ecosystems. Furthermore, inappropriate wastedisposal handling and particularly common discharge technique used by TNT producing plants lead to increased concentration of this pollutant in ecosystem (Pennington and Brannon, 2002). TNT is well known to have toxic, mutagenic and carcinogenic effects on various organisms, including eukaryotes and prokaryotes; as a result, it is listed as a class C potential carcinogen by the US Environmental Protection Agency, EPA (Stanley et al., 2015). Biotransformation of TNT is of considerable importance, as it is crucial to reduce the negative effects of TNT on living organisms and remove the detrimental effects of this contaminant on the environment. Several physicochemical methods, e.g. thermal decomposition, s
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