Paraffinic n-alkanes (C22-C30), crucial portions of residual oil, are generally considered to be difficult to be biodegraded owing to their general solidity at ambient temperatures and low water solubility, rendering relatively little known about metabolic processes in different methanogenic hydrocarbon-contaminated environments. Here, we established a methanogenic C22-C30 n-alkane-degrading enrichment culture derived from a high-temperature oil reservoir production water. During two-year incubation (736 days), unexpectedly significant methane production was observed. The measured maximum methane yield rate (164.40 μmol L-1 d-1) occurred during the incubation period from day 351 to 513. The nearly complete consumption (> 97%) of paraffinic n-alkanes and the detection of dicarboxylic acids in n-alkane-amended cultures indicated the biotransformation of paraffin to methane under anoxic condition. 16S rRNA gene analysis suggested that the dominant methanogen in n-alkane-degrading cultures shifted from Methanothermobacter on day 322 to Thermoplasmatales on day 736. Bacterial community analysis based on high-throughput sequencing revealed that members of Proteobacteria and Firmicutes exhibiting predominant in control cultures, while microorganisms affiliated with Actinobacteria turned into the most dominant phylum in n-alkane-dependent cultures. Additionally, the relative abundance of mcrA gene based on genomic DNA significantly increased over the incubation time, suggesting an important role of methanogens in these consortia. This work extends our understanding of methanogenic paraffinic n-alkanes conversion and has biotechnological implications for microbial enhanced recovery of residual hydrocarbons and effective bioremediation of hydrocarbon-containing biospheres.

中文翻译：

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长链正构烷烃的生物降解与从高温油层的采出水富集的培养物中的甲烷生产偶联。

链烷烃正构烷烃（C22-C30）是残油的关键部分，由于其在环境温度下的总体固性和低水溶性而通常被认为难以生物降解，这使得对不同产甲烷烃的代谢过程的了解相对较少。受污染的环境。在这里，我们建立了由高温油藏生产水衍生的产甲烷的C22-C30正构烷烃降解富集培养物。在两年的培养中（736天），观察到了意想不到的大量甲烷生成。在第351天到513天的潜伏期中，测得的最大甲烷产率（164.40μmolL-1 d-1）。几乎完全消耗（> 97％的链烷烃正构烷烃和在正构烷烃修饰的培养物中检测到的二元羧酸表明，在缺氧条件下，链烷烃已生物转化为甲烷。16S rRNA基因分析表明，正构烷烃降解培养物中的主要产甲烷菌从第322天的甲烷嗜热菌转移到了第736天的嗜热菌。基于高通量测序的细菌群落分析表明，变形杆菌和Firmicutes成员在对照培养物中占主导地位，而放线菌属的微生物在正构烷烃依赖性培养中变成了最主要的门。此外，基于基因组DNA的mcrA基因的相对丰度随着孵育时间的增加而显着增加，表明产甲烷菌在这些联合体中的重要作用。