氧气对厌氧煤层菌群产甲烷能力及菌群组成影响

Influences of air exposure on methane production and composition of microbiome from coalbed formation water

摘要:

微生物增产煤层气成为近年来煤层气领域的研究重点。作为产甲烷过程中的核心微生物——产甲烷古菌，通常是严格厌氧，对氧气敏感。【目的】为了解煤层气产出水厌氧富集培养并进行空气暴露后，产甲烷潜力及菌群结构的变化情况。选取不同煤层气产区煤层产出水，经厌氧富集培养后进行空气暴露实验，探究暴露于好氧环境后菌群的产甲烷能力以及微生物群落变化，可为未来规模化厌氧发酵产物在煤层原位利用煤产气工艺开发提供科学参考。【方法】以鄂尔多斯盆地东缘地区韩城(HC)、保德(BD)和临汾(LF)3个区块煤层产出水菌群富集产物为研究对象，进行空气暴露实验，在24 h内连续取样，空气暴露后菌液再次接种培养，进行厌氧产气能力监测及微生物菌群组成多样性分析，评估混合菌群对有氧环境的耐受程度及产甲烷能力，同时观察菌群变化情况。【结果】回接培养后，由产甲烷结果可知，三区块空气暴露24 h后微生物仍具有产气能力，而且产气能力与未经空气暴露相当。菌群分析发现：参与前期水解、酸化及乙酸化过程的细菌主要为厚壁菌门(Firmicutes)、互养菌门(Synergistetes)、变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)，产甲烷古菌主要为广古菌门(Euryarchaeota)的甲烷八叠球菌属(Methanosarcina)、产甲烷袋菌属(Methanofollis)和甲烷杆菌属(Methanobacterium)。【结论】在经历24 h空气暴露后，煤层产出水微生物菌群产甲烷能力并未受到影响，产甲烷能力与未接触空气菌群相当；参与甲烷生成菌群组成及菌群变化也不明显，但不同类型微生物的相对丰度有一定变化。本研究有望在厌氧富集菌液应用于煤层原位降解产甲烷工程化应用中具有广泛的应用前景。

Abstract:

Microbially enhanced coalbed methane production has become a research hotspot of coalbed methane production in recent years. Methanogens, the essential microorganisms in coalbed methane production, are usually strictly anaerobic and sensitive to oxygen. [Objective] To understand the changes in the methane production and composition of the anaerobic microbiome after exposure to oxygen, we conducted the enrichment culture of coalbed formation water collected from different regions along the east edge of Ordos Basin in China for air exposure experiments. Our findings are expected to provide scientific support for the future in-situ utilization of large-scale anaerobic fermentation products in coalbed methane production. [Methods] We used the enrichment cultures of coalbed formation water collected from Hancheng (HC), Baode (BD), and Linfen (LF) for air exposure for a series of time schedules within 24 h. The air-exposed enrichment cultures were re-inoculated and cultured. The methane production and community succession were analyzed to evaluate the microbiome tolerance to the aerobic condition. [Results] The microorganisms in all the three regions were still active after 24 hours of air exposure and showed the methane production comparable to that before air exposure. The dominant groups involved in the hydrolysis, acidification, and acetoxylation mainly included Firmicutes, Synergistetes, Proteobacteria, and Bacteroidetes. Methanogenic archaea were mainly Methanosarcina, Methanofollis, and Methanobacterium, belonging to Euryarchaeota. [Conclusion] After 24 hours of air exposure, the methane-producing capacity of the microbiome from the coalbed formation water was not affected and was comparable to that before air exposure. The microbiome did not showcase obvious succession, while the relative abundance of different groups changed accordingly. Our study can give scientific support for the in-situ industrial application of anaerobic enrichment culture from deep coalbed seams during coal degrading in methane production.