Abstract
In this study, hydrogenotrophic methanogenic mixed cultures taken from 13 lab-scale ex-situ biogas upgrading systems under different temperature (20–70 °C), pH (6.0–8.5), and CO (0–10%, v/v) variables were systematically investigated. High-throughput 16S rRNA gene sequencing was used to identify the microbial consortia, and statistical analyses were conducted to reveal the microbial diversity, the core functional microbes, and their correlative relationships with tested variables. Overall, bacterial community was more complex than the archaea community in all mixed cultures. Hydrogenotrophic methanogens Methanothermobacter, Methanobacterium, and Methanomassiliicoccus, and putative syntrophic acetate-oxidizing bacterium Coprothermobacter and Caldanaerobacter were found to predominate, but the core functional microbes varied under different conditions. Multivariable sensitivity analysis indicated that temperature (p < 0.01) was the crucial variable to determine the microbial consortium structures in hydrogenotrophic methanogenic mixed cultures. pH (0.01 < p < 0.05) significantly interfered with the relative abundance of dominant archaea. Although CO did not affect community (p > 0.1), some potential CO-utilizing syntrophic metabolisms might be enhanced. Understanding of microbial consortia in the hydrogenotrophic methanogenic mixed cultures related to environmental variables was a great advance to reveal the microbial ecology in microbial biogas upgrading process.
Highlights
Biogas upgrading via an external H2 supply to promote CO2 biomethanation has attracted considerable attention [1]
Microbial analysis conducted in various biogas upgrading configurations revealed that the Methanobacterium, Methanothermobacter, Methanoculleus, and Methanomicrobium species were dominant in the hydrogenotrophic methanogenic consortium [3,5,9,10,11,12]
The utilization of hydrogenotrophic methanogenic mixed cultures enriched by H2 were found to be more efficient in CO2 biomethanation, giving larger CH4 yields compared to the utilization of pure cultures [13], for example, of Methanothermobacter thermautotrophicus [14]
Summary
Biogas upgrading via an external H2 supply to promote CO2 biomethanation has attracted considerable attention [1]. It was reported that the methane content in biogas could be increased up to 89–96% by hydrogenotrophic methanogens in various in-situ and ex-situ CO2 biomethanation processes [4,5,6,7,8]. Microbial analysis conducted in various biogas upgrading configurations revealed that the Methanobacterium, Methanothermobacter, Methanoculleus, and Methanomicrobium species were dominant in the hydrogenotrophic methanogenic consortium [3,5,9,10,11,12]. The utilization of hydrogenotrophic methanogenic mixed cultures enriched by H2 were found to be more efficient in CO2 biomethanation, giving larger CH4 yields compared to the utilization of pure cultures [13], for example, of Methanothermobacter thermautotrophicus [14]. The practical application of mixed adapted cultures is preferable as compared with pure cultures [13], due to its advantages of the greater robustness of the microbial community, flexible process control, and increased cost-effectiveness [15,16,17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
