Hexadecane-degradation by Teskumurella and Stenotrophomonas Strains Isolated From Hydrocarbon Contaminated Soils

Background: Petroleum hydrocarbons are mix compounds and divided into four groups: Saturates, Aromatics, Resins and Asphalten. Among various phases of crude-oil, the alkanes with medium length chain are favorable substrates that rapidly degraded, although short-chain alkanes are very toxic and long-chain alkanes have low solubility in water that reduce its bioavailability and make resistant to biodegradation. Objectives: The main goal of this study is the isolation, molecular identification and degradation properties of hexadecane degrading bacteria from contaminated soils. Materials and Methods: In this research to isolate aliphatic degrading bacteria, sampling from hydrocarbon contaminated soil with of petroleum reservoirs regions, Tehran were performed. Alkane degrading bacteria were isolated by enrichment in Bushnel-Hass medium with hexadecane as sole source of carbon and energy. The isolated strains were identified by amplification of 16S rDNA gene and sequencing. Alkane hydroxylase gene (alk-B) was identified in all strains by PCR with specific primers. Results: Among 8 strains three strains with high growth rate on hexadecane selected for further study. These three selected strains identified as Stenotrophomonas maltophilia strain M2, S. maltophilia strain Q2 and Tsukamurella tyrosinosolvens strain Q3. In comparison to the other bacteria, these bacterial strains can degrade hexadecane 2 times more; with a high emulsification activity. Conclusions: The 2.5% concentration of hexadecane was the best concentration that supports the growth of these strains. Among these strain T. tyrosinosolvens strain Q3 was the best strain for biodegradation of hexadecane. Alk-B gene was identified in all strains.