Methanogenic potential and community structure of coalbed-methane production water microbiome

Abstract:

Biogenetic coalbed methane is a significant composition in Erlian and Hailar basins. However, little information is available how biogenetic coalbed methane is generated. [Objective] To evaluate the methanogenic potential of volatile fatty acids by the coalbed-methane production water microbiome, and to observe the shift of microbial community structure involved. [Methods] Simulation experiments were performed by inoculating coalbed-methane production water from four coalbed methane wells of Erlian and Hailar basins. Acetate, propionate and butyrate were selected as substrates. Methane production and substrate utilization were measured over time. The microbial communities of coalbed methane production water and enrichment cultures after incubation were analyzed through high-throughput sequencing of 16S rRNA gene. [Results] With the exception of H303 coalbed water without propionate degradation, all coalbed water microbiomes had the ability to degrade acetate, propionate and butyrate under methanogenic degradation. The maximum specific methane production rate, substrate conversion ratio and lag-phase period exhibited great difference in different volatile fatty acid group. The maximum specific methane production rate and substrate conversation ratio was highest in the butyrate group and the lag-phase was the shortest with acetate addition. High-throughput sequencing analysis reveals that the archaeal community structure of enrichment cultures was significantly correlated with the source of coalbed water. The predominant archaeal groups of Erlian basin were hydrogenotrophic Methanocalculus (13.5%-63.4%) and Methanosarcina (7.9%-51.3%). The predominant archaea of Hailar basin were hydrogenotrophic Methanobacterium (24.3%-57.4%) and Methanosarcina (29.6%-66.5%). The enriched bacterial community structure is significantly correlated with substrates, sulfate-reducing Desulfovibrio (12.0%-41.0%), syntrophic propionate-degrading Syntrophobacter (39.63%-75.45%) and syntrophic butyrate-degrading Syntrophomonas (8.5%-21.9%) were enriched in acetate, propionate and butyrate group, respectively. [Conclusion] The coalbed-methane production water microbiome possessed potential of methanogenic volatile fatty acid degradation, among which acetate was probably fermented by methanogens, propionate and butyrate are consumed by syntrophic bacteria Syntrophobacter and Syntrophomonas respectively. This result will contribute to the development research of microbial enhanced methane recovery from coalbed.