RESEARCH ARTICLE Biodegradation of C.I. Acid Red 1 by indigenous bacteria Stenotrophomonas sp. BHUSSp X2 isolated from dye contaminated soil Lata Kumari 1 & Dhanesh Tiwary 1 & Pradeep Kumar Mishra 2 Received: 15 December 2014 /Accepted: 9 March 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract A significant proportion of xenobiotic recalcitrant azo dyes are being released in environment during carpet dye- ing. The bacterial strain Stenotrophomonas sp. BHUSSp X2 was isolated from dye contaminated soil of carpet industry, Bhadohi, India. The isolated bacterial strain was identified mor- phologically, biochemically, and on the basis of 16S rRNA gene sequence. The isolate decolorized 97 % of C.I. Acid Red 1 (Acid RED G) at the concentration of 200 mg/l within 6 h under optimum static conditions (temperature -35 °C, pH 8, and initial cell concentration 7×10 7 cell/ml). Drastic reduction in dye degradation rate was observed beyond initial dye concentration from 500 mg/l (90 %), and it reaches to 25 % at 1000 mg/l under same set of conditions. The analysis related to decolorization and degradation was done using UV-Vis spec- trophotometer, HPLC, and FTIR, whereas the GC-MS tech- nique was utilized for the identification of degradation prod- ucts. Phytotoxicity analysis revealed that degradation products are less toxic as compared to the original dye. Keywords Xenobiotic . Stenotrophomonas sp. BHUSSp X2 . C.I. Acid Red 1 . Decolorization . Toxicity . Biotransformation . Biodegradation Introduction The effluents discharged by industries such as carpet, textile, leather, pharmaceuticals, food, cosmetics, and printing contain azo dye (10–15 %) (Forgacs et al. 2004; Vimonses et al. 2010; Robinson et al. 2001), which are considered to be the most hazardous among xenobiotics. The Acid Red G is one of the popular azo dyes that has been extensively used for the dyeing wool, nylon, and silk fibers (Ozcan et al. 2004; Vimonse et al. 2010). Azo dyes are being recalcitrant and toxic in nature which create havoc to flora and fauna. The discharge of these effluents into nearby water bodies leads to the reduction in sunlight penetration and dissolved oxygen content of water- ways; hence, increase in biological oxygen demand and chem- ical oxygen demand adversely affect the water quality (Jonstrup et al. 2011; Meng et al. 2012). It is also well docu- mented that synthetic dyes and their metabolites are toxic, carcinogenic, and mutagenic in nature (De Aragao Umbuzeiro et al. 2005; Tan et al. 2005). To overcome these problems, effluent standard has to be achieved prior to disposal to sur- face bodies. There are various physical and chemical methods for treatment such as adsorption, photoionization, electrolysis, oxidation, and neutralization that have limitations like high cost, low efficiency, and production of secondary toxic inter- mediates (Asad et al. 2007; Zainal et al. 2005; Harrelkas et al. 2008; Asad et al. 2007). Due to cost effectiveness and ecolog- ical compatibility, bioremediation of such effluents is most promising technology (Baban et al. 2010; Spagni et al. 2010; Kolekar et al. 2012). Responsible editor: Philippe Garrigues Highlights • Isolation and identification of bacterial strain BHUSSp X2. • Application of the isolate for azo dye degradation. • The detection of biotransformation pathways for Acid Red G dye using GC-MS and identification of enzyme involved in degradation. Electronic supplementary material The online version of this article (doi:10.1007/s11356-015-4351-8) contains supplementary material, which is available to authorized users. * Pradeep Kumar Mishra pkmishra.che@itbhu.ac.in 1 Department of Chemistry, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005, India 2 Department of Chemical Engineering and Technology, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005, India Environ Sci Pollut Res DOI 10.1007/s11356-015-4351-8