State Key Laboratory of Bioreactor Engineering and School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, People's Republic of China.
School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region, People's Republic of China.
Appl Microbiol Biotechnol. 2019 Mar;103(5):2391-2401. doi: 10.1007/s00253-018-09574-1. Epub 2019 Jan 4.
Branched alkanes are important constituents of crude oil and are usually regarded as resistant to microbial degradation, resulting in little knowledge of biochemical processes involved in anaerobic branched alkanes biodegradation. Here, we initiated an incubation study by amendment of iso-C9 (2-methyl, 3-methyl, and 4-methyloctane) as substrates for methanogenic degradation in production water from a high-temperature petroleum reservoir. Over an incubation period of 367 days, significant methanogenesis was observed in samples amended with these branched alkanes. The strong methanogenic activity only observed in iso-C9 amendments suggested the presence of microbial transformation from iso-alkanes into methane. GC-MS-based examination of the original production water identified an intermediate tentatively to be iso-C9-like alkylsuccinate, but was not detected in the enrichment cultures, combined with the successful amplification of assA functional gene in inoculating samples, revealing the ability of anaerobic biodegradation of iso-C9 via fumarate addition pathway. Microorganisms affiliated with members of the Firmicutes, Synergistetes, and methanogens of genus Methanothermobacter spp. were highly enriched in samples amended with iso-C9. The co-occurrence of known syntrophic acetate oxidizers Thermoacetogenium spp. and Methanothermobacter spp. (known hydrogenotrophic methanogens) indicates a potential syntrophic acetate oxidation associated with the methanogenic biodegradation of iso-C9. These results provide some useful information on the potential biodegradation of branched alkanes via methanogenesis and also suggest that branched alkanes are likely activated via fumarate addition in high-temperature petroleum reservoirs.
支链烷烃是原油的重要组成部分，通常被认为对微生物降解具有抗性，因此人们对参与厌氧支链烷烃生物降解的生化过程知之甚少。在这里，我们通过在来自高温油藏的生产水中添加异 -C9（2-甲基、3-甲基和 4-甲基辛烷）作为甲烷生成降解的底物，启动了一项培养研究。在 367 天的培养期内，在添加这些支链烷烃的样品中观察到明显的产甲烷作用。仅在异 -C9 添加剂中观察到的强烈产甲烷活性表明存在微生物将异烷烃转化为甲烷的过程。基于 GC-MS 的原始生产水分析鉴定出一种中间产物，推测为异 -C9 类似的烷基琥珀酸酯，但在富集培养物中未检测到，再加上在接种样品中成功扩增了 assA 功能基因，揭示了通过富马酸盐添加途径进行厌氧生物降解异 -C9 的能力。在添加异 -C9 的样品中高度富集了与厚壁菌门、互养菌门和 Methanothermobacter 属的产甲烷菌成员相关的微生物。在添加异 -C9 的样品中，同时存在已知的协同乙酸氧化菌 Thermoacetogenium 属和 Methanothermobacter 属（已知的氢营养型产甲烷菌），这表明与异 -C9 的产甲烷生物降解相关的潜在协同乙酸氧化作用。这些结果为支链烷烃通过产甲烷作用进行潜在生物降解提供了一些有用信息，并表明支链烷烃在高温油藏中可能通过富马酸盐添加而被激活。
