초록
<P><B>Abstract</B></P> <P>In this study, hydrogenotrophic methanogenesis with respect to methanogenic activity and microbial structures under extreme-thermophilic conditions were examined, and compared with the conventional thermophilic condition. The hydrogenotrophic methanogens were successfully acclimated to the temperatures of 55, 65 and 70 °C. Although acclimation was slower at 65 and 70 °C, hydrogenotrophic methanogenesis remained fairly stable. High-throughput sequencing using 16S rRNA analysis showed that the higher temperatures resulted in single archaea community dominated by hydrogenotrophic <I>Methanothermobacter</I>. Moreover, the syntrophic bacteria changed from <I>Coprothermobacter</I> and <I>Thermodesulfovibrio</I> at 55 °C to <I>Thermodesulfovibrio</I> at 70 °C. Specific hydrogenotrophic methanogenic rate at 70 °C was 98.6 ± 4.2 Nml CH<SUB>4</SUB>/g VS/hr, which was over 4-folds higher than that 8at 55 °C. The lag phase under extreme-thermophilic conditions was longer than thermophilic condition, which was probably due to the archaeal structure with low diversity. Extreme-thermophilic condition resulted in a shift in methanogenesis pathway from acetoclastic methanogenesis to hydrogenotrophic methanogenesis with the enrichment of <I>Methanothermobacter thermautotrophicus.</I> </P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogenotrophic methanogenesis was stable under extreme-thermophilic condition. </LI> <LI> Higher CH<SUB>4</SUB> rate was achieved at 70 °C, but with longer lag phase. </LI> <LI> Homogenous archaea and diversified bacteria community were obtained at 65 and 70 °C. </LI> <LI> <I>Methanothermobacter thermautotrophicus</I> was dominant with 92% at 70 °C. </LI> <LI> Dominant bacteria were syntrophically related to <I>M</I>. <I>thermautotrophicus</I>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>