Long-Term Incubation Reveals Methanogenic Biodegradation of C5 and C6 iso-Alkanes in Oil Sands Tailings

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• 作者：Tariq Siddique ; Mohd Faidz Mohamad Shahimin ; Saima Zamir ; Kathleen Semple ; Carmen Li ; Julia M. Foght
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：December 15, 2015
• 年：2015
• 卷：49
• 期：24
• 页码：14732-14739
• 全文大小：420K
• ISSN：1520-5851

文摘

iso-Alkanes are major components of petroleum and have been considered recalcitrant to biodegradation under methanogenic conditions. However, indigenous microbes in oil sands tailings ponds exposed to solvents rich in 2-methylbutane, 2-methylpentane, 3-methylpentane, n-pentane, and n-hexane produce methane in situ. We incubated defined mixtures of iso- or n-alkanes with mature fine tailings from two tailings ponds of different ages historically exposed to different solvents: one, 鈭?0 years old, receiving C₅鈥揅₆ paraffins and the other, 鈭?5 years old, receiving naphtha. A lengthy incubation (>6 years) revealed iso-alkane biodegradation after lag phases of 900鈥?800 and 鈭?80 days, respectively, before the onset of methanogenesis, although lag phases were shorter with n-alkanes (鈭?50鈥?675 and 鈭?70 days, respectively). 2-Methylpentane and both n-alkanes were completely depleted during 鈭?400 days of incubation, whereas 2-methylbutane and 3-methylpentane were partially depleted only during active degradation of 2-methylpentane, suggesting co-metabolism. In both cases, pyrotag sequencing of 16S rRNA genes showed codominance of Peptococcaceae with acetoclastic (Methanosaeta) and hydrogenotrophic (Methanoregula and Methanolinea) methanogens. These observations are important for predicting long-term greenhouse-gas emissions from oil sands tailings ponds and extend the known range of hydrocarbons susceptible to methanogenic biodegradation in petroleum-impacted anaerobic environments.