ENVIRONMENTAL BIOTECHNOLOGY Biodegradation of polycyclic aromatic hydrocarbons by a halophilic microbial consortium Seyed Mohammad Mehdi Dastgheib & Mohammad Ali Amoozegar & Khosro Khajeh & Mahmoud Shavandi & Antonio Ventosa Received: 3 August 2011 /Revised: 20 October 2011 /Accepted: 2 November 2011 /Published online: 16 November 2011 # Springer-Verlag 2011 Abstract In this study we investigated the phenanthrene degradation by a halophilic consortium obtained from a saline soil sample. This consortium, named Qphe, could efficiently utilize phenanthrene in a wide range of NaCl concentrations, from 1% to 17% (w/v). Since none of the purified isolates could degrade phenanthrene, serial dilu- tions were performed and resulted in a simple polycyclic aromatic hydrocarbon (PAH)-degrading culture named Qphe-SubIV which was shown to contain one culturable Halomonas strain and one unculturable strain belonging to the genus Marinobacter . Qphe-SubIV was shown to grow on phenanthrene at salinities as high as 15% NaCl (w/v) and similarly to Qphe, at the optimal NaCl concentration of 5% (w/v), could degrade more than 90% of the amended phenanthrene in 6 days. The comparison of the substrate range of the two consortiums showed that the simplified culture had lost the ability to degrade chrysene but still could grow on other polyaromatic substrates utilized by Qphe. Metabolite analysis by HPLC and GC–MS showed that 2-hydroxy 1-naphthoic acid and 2-naphthol were among the major metabolites accumulated in the Qphe- SubIV culture media, indicating that an initial dioxygena- tion step might proceed at C1 and C2 positions. By investigating the growth ability on various substrates along with the detection of catechol dioxygenase gene, it was postulated that the uncultured Marinobacter strain had the central role in phenanthrene degradation and the Halomo- nas strain played an auxiliary role in the culture by utilizing phenanthrene metabolites whose accumulation in the media could be toxic. Keywords Polycyclic aromatic hydrocarbons (PAHs) . Phenanthrene . Biodegradation . Halophile . Marinobacter . Halomonas . Consortium Introduction Saline environments are particularly susceptible to petro- leum contamination due to their close association with oil industries (Dastgheib et al. 2011), and among various petroleum compounds, polycyclic aromatic hydrocarbons (PAHs) consisting of two or more fused aromatic rings are of great concern as ubiquitous pollutants with toxic and carcinogenic potential (Menzie et al. 1992). In spite of their chemical stability and very low water solubility and bioavailability, numerous bacterial species have been de- S. M. M. Dastgheib Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran M. A. Amoozegar (*) Extremophile Laboratory, Department of Microbiology, School of Biology, College of Science, University of Tehran, P. O. Box 14155-6455, Tehran, Iran e-mail: amozegar@khayam.ut.ac.ir K. Khajeh Department of Biochemistry, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran M. Shavandi Biotechnology Research Center, Research Institute of Petroleum Industries, Tehran, Iran A. Ventosa Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, Seville, Spain Appl Microbiol Biotechnol (2012) 95:789–798 DOI 10.1007/s00253-011-3706-4