Preservation and methane production of methanogenic microbial consortia from coal geological environment in Sihe Mine

Abstract:

[Background] Methanogenic microbial consortia from coal geological environment can metabolize coal matrix to produce methane, which is of great significance for realizing the reutilization of coalbed methane (CBM) resources. [Objective] In order to prove the feasibility of the methods of culture preservation, community dynamics of methanogens was analyzed and the yeild of methane was tested during the preservation process. Meanwhile, the results would give theoretic basis for microbial enhanced CBM. [Methods] Three culture preservation methods involving glycerol/L-cysteine, eutrophication, and coal-basic salt method were compared at different temperatures. Microbial methanogenic activity in different preservations was tested by gas production. In addition, the compositions of microbial community in coal and basic salt preservation at 25 °C were studied by 454 high-throughput sequencing technology for 16S rRNA genes of bacteria and archaea. [Results] The preservation methods of 9 groups were compared, and the best culture preservation was the coal and basic salt preservation at 25 °C. Under this condition, the microbial methanogenic activity and the methane production were the highest. The yeild of methane was 12% to 25% and 24% to 73% using anthracite and lignite as carbon sources, respectively. In the coal and basic salt preservation test, the dominant bacteria and archaea in the early period were Pseudomonas and Methanosarcina at 25 °C, respectively. The structure of bacterial community changed dramatically with preservation time. The dominant bacteria changed to fermentative bacteria and acetogenic bacteria. The composition of dominant archaea was relatively stable. [Conclusion] The best preservation was coal and basic salt preservation at 25 °C, in which microbial activity of methanogens could be sustained at a better status and methanogens had good methane production ability.