title: Biodegradation of 4-nitrotoluene with biosurfactant production by Rhodococcus pyridinivorans NT2: metabolic pathway, cell surface properties and toxicological characterization.
abstract: A novel 4-nitrotoluene-degrading bacterial strain was isolated from pesticides contaminated effluent-sediment and identified as Rhodococcus pyridinivorans NT2 based on morphological and biochemical properties and 16S rDNA sequencing. The strain NT2 degraded 4-NT (400 mg l(-1)) with rapid growth at the end of 120 h, reduced surface tension of the media from 71 to 29 mN m(-1) and produced glycolipidic biosurfactants (45 mg l(-1)). The biosurfactant was purified and characterized as trehalose lipids. The biosurfactant was stable in high salinity (10 % w/v NaCl), elevated temperatures (120 °C for 15 min) and a wide pH range (2.0-10.0). The noticeable changes during biodegradation were decreased hydrophobicity; an increase in degree of fatty acid saturation, saturated/unsaturated ratio and cyclopropane fatty acid. Biodegradation of 4-NT was accompanied by the accumulation of ammonium (NH4 (+)) and negligible amount of nitrite ion (NO2 (-)). Product stoichiometry showed a carbon (C) and nitrogen (N) mass balance of 37 and 35 %, respectively. Biodegradation of 4-NT proceeded by oxidation at the methyl group to form 4-nitrobenzoate, followed by reduction and hydrolytic deamination yielding protocatechuate, which was metabolized through β-ketoadipate pathway. In vitro and in vivo acute toxicity assays in adult rat (Rattus norvegicus) showed sequential detoxification and the order of toxicity was 4-NT >4-nitrobenzyl alcohol >4-nitrobenzaldehyde >4-nitrobenzoate >> protocatechuate. Taken together, the strain NT2 could be used as a potential bioaugmentation candidate for the bioremediation of contaminated sites.
authors: School of Life Sciences, North Maharashtra University, Jalgaon, 425 001, Maharashtra, India.
authors: Debasree
authors: D
authors: Kundu
authors: Chinmay
authors: C
authors: Hazra
authors: Navin
authors: N
authors: Dandi
authors: Ambalal
authors: A
authors: Chaudhari
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D005227:Fatty Acids / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D053858:Metabolic Networks and Pathways / Q000187:drug effects*; D010802:Phylogeny; D051381:Rats; D012240:Rhodococcus / Q000166:cytology* / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared; D013501:Surface-Active Agents / Q000378:metabolism*; D014050:Toluene / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity
chemical_list: D005227:Fatty Acids; D013501:Surface-Active Agents; D014050:Toluene; C017572:4-nitrotoluene