Biotransformation of nitroaromatics and their effects on mixed function oxidase system
Department of Chemistry, University of Pune, Pune 411 007, India Enzyme and Microbial Technology
(Impact Factor: 2.32).
10/2005; 37(5):527-533. DOI: 10.1016/j.enzmictec.2005.03.011
Acinetobacter junii A8 was able to biotransform nitroaromatic compounds like o-nitroaniline, o-nitrotoluene, m-nitrotoluene, 2,4,6-trinitrotoluene and o-nitrophenol under aerobic condition, within 36 h of incubation. These compounds, which are normally considered to be toxic to microorganisms, caused the induction of drug metabolizing enzymes such as cytochrome P-450, aminopyrine N-demethylase, acetanilide hydroxylase and glutathione S-transferase. These enzymes constitute the bacterial mixed function oxidase system. Induction of this system implies its involvement in biotransformation of these nitro compounds. The biotransformed metabolites were characterized by IR, 1H NMR and GC–mass spectroscopy. It was observed that o-nitroaniline and m-nitrotoluene were reduced to their respective amines, whereas o-nitrotoluene was oxidized to acid. However, 2,4,6-trinitrotoluene (TNT) and o-nitrophenol were completely mineralized. The metabolites of TNT biotransformation were characterized as 2,6-dinitro-4-nitrosotoluene, 4-amino-2,6-dinitrotoluene and 4-amino-2,6-dinitrobenzoic acid. The result of this study showed that these nitroaromatics induced the mixed function oxidase system, which resulted in the degradation of these compounds.
Available from: Evguenii I Kozliak
- "The majority of DNP microbial degraders are heterotrophic bacteria, such as Pseudomonas putida (Zeyer and Kearney 1984; Bruhn et al. 1987; Meulenberg et al. 1996), Alcaligenes eutrophus (Ecker et al. 1992; Xiao et al. 2007), Burkholderia sp. (Prakash et al. 1996; Iwaki et al. 2007), Rhodococcus opacus (Gemini et al. 2007; Martinkova et al. 2009), Acinetobacter junii (Soojhawon et al. 2005), Moraxella sp. (Spain and Gibson 1991; Leung et al. 2005), Arthrobacter protophormiae (Chauhan et al. 2000), or Bacillus sphaericus (Kadiyala et al. 1998). "
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ABSTRACT: Aerobic biodegradation of 2,4-dinitrophenol (2,4-DNP) and 2,6-DNP by an immobilized mixed microbial community in packed-bed reactors was compared for individual components and in a mixture. The reactors efficiently (>97 %) removed higher 2,4-DNP concentrations (up to 43 g m−3) compared to 2,6-DNP (−3), the former being metabolized with higher degradation rates. Similar loadings of both DNPs were efficiently degraded (>95 %) when treated as a mixture; i.e., the 2,6-DNP removal efficiency was positively affected by the presence of 2,4-DNP when low concentrations of both pollutants were treated. However, an increase of the total DNP concentration to 41 g m−3 led to a sizable drop of the degradation rate in the mixture but not when the substrates were treated separately.
Available from: Chetan C Oturkar
- "Strain CH1 was isolated from soil at an effluent disposal site of a textile-dyeing plant located in Solapur, Maharashtra, India using the methodology of Seesuriyachan et al. (2007). The isolate CH1 was grown in Nutrient Broth (NB) (Soojhawon et al., 2005) containing (g/l) peptone, 5; yeast extract, 5; NaCl, 5. The isolate was submitted to Genome Biolab, Pune, India, for identification by 16S rRNA gene sequencing. The Genomic DNA was isolated from pure culture using the DNAzol method (Chomczynski et al., 1997). "
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ABSTRACT: Bacillus lentus BI377, isolated from textile effluent-contaminated soil, was able to degrade 97% and 92% of Reactive Red 120 dye when 1200 and 1500 mg/l, respectively, of dye was added to nutrient broth (NB) at 35 °C within 12 h. UV-vis spectroscopy, GC-MS, FTIR and 1H NMR revealed the formation of catechol which may be further utilized by the bacterium via the TCA cycle, leading to complete mineralization. Structural analysis of metabolites in conjunction with enzyme activity studies confirmed the involvement of azoreductase, cytochrome P450 monooxygenase and other antioxidant enzymes. Decreases in total organic carbon and in biological and chemical oxygen demand suggest formation of low molecular weight metabolites that could be completely mineralized. These results suggest the potential use of B. lentus BI377 towards online treatment of textile dye effluents by using an appropriate bioreactor over a wide range of pH. This study opens-up a dependable and proficient way to use industrially viable non-pathogenic strains for biotransformation of carcinogenic dyes to ecofriendly compounds.
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ABSTRACT: Certain drugs containing a nitroaromatic moiety (e.g., tolcapone, nimesulide, nilutamide, flutamide, nitrofurantoin) have been associated with organ-selective toxicity including rare cases of idiosyncratic liver injury. What they have in common is the potential for multistep nitroreductive bioactivation (6-electron transfer) that produces the potentially hazardous nitroanion radical, nitroso intermediate, and N-hydroxy derivative. These intermediates have been associated with increased oxidant stress and targeting of nucleophilic residues on proteins and nucleic acids. However, other mechanisms including the formation of oxidative metabolites and mitochondrial liability, as well as inherent toxicokinetic properties, also determine the drugs' overall potency. Therefore, structural modification not only of the nitro moiety but also of ring substituents can greatly reduce toxicity. Novel concepts have revealed that, besides the classical microsomal nitroreductases, cytosolic and mitochondrial enzymes including nitric oxide synthase can also bioactivate certain nitroarenes (nilutamide). Furthermore, animal models of silent mitochondrial dysfunction have demonstrated that a mitochondrial oxidant stress posed by certain nitroaromatic drugs (nimesulide) can produce significant mitochondrial injury if superimposed on a genetic mitochondrial abnormality. Finally, there may be mechanisms for all nitroaromatic drugs that do not involve bioactivation of the nitro group, e.g., AHR interactions with flutamide. Taken together, the focus of research on the hepatic toxicity of nitroarene-containing drugs has shifted over the past years from the identification of the reactive intermediates generated during the bioreductive pathway to the underlying biomechanisms of liver injury. Most likely one of the next paradigm shifts will include the identification of determinants of susceptibility to nitroaromatic drug-induced hepatotoxicity.
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