Degradation of benzene, toluene, and xylene (BTX) from aqueous solution by isolated bacteria from contaminated sites A. Mesgari Shadi • S. Yaghmaei • F. Vafaei • A. R. Khataee • M. S. Hejazi Received: 21 February 2013 / Accepted: 3 April 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract The present study was carried out to evaluate the degradation efficiency of benzene, toluene, and xylene (BTX) by isolated bacteria from various petroleum- hydrocarbons contaminated sites. Five isolated bacteria were selected for testing BTX biodegradation from liquid culture media. Each of these bacteria was able to degrade BTX but with different efficiencies. Maximum biodegradation efficiency for benzene (more than 70 %) was obtained by Gram-positive coccobacillus, Gram- positive coccus and Gram-negative bacillus bacteria, for toluene (60 %) and xylene (70 %) by Gram-positive coccobacillus and Gram-negative coccobacillus. It was found that the presence of xylene in the substrate mixture caused considerable reduction in toluene and benzene biodegradation efficiency. Keywords Aromatic hydrocarbons  Bacteria  Biodegradation  Wastewater treatment Introduction Benzene, toluene, and xylene (BTX) release into the environment causes very severe public health problems. These compounds have neurotoxic, mutagenic, and carcinogenic effects not only for humans but also for flora and fauna and other A. Mesgari Shadi  S. Yaghmaei Chemical & Petroleum Engineering Department, Sharif University of Technology, Tehran, Iran A. Mesgari Shadi  M. S. Hejazi Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran F. Vafaei  A. R. Khataee (&) Research Laboratory of Advanced Water and Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, Iran e-mail: a_khataee@tabrizu.ac.ir 123 Res Chem Intermed DOI 10.1007/s11164-013-1189-x