초록
<P><B>Abstract</B></P> <P>In this study, the effects of four types of organic compounds (tryptone, acetate/propionate, glucose and ethanol) on methanogenesis, electron transfer processes and microbial community structure were examined. When tryptone and acetate/propionate were used, the dominant methanogenic pathway was aceticlastic methanogenesis and <I>Methanosarcina</I> was the most abundant methanogen. When glucose or ethanol were provided as the external carbon source, the aceticlastic and hydrogenotrophic pathways were utilised simultaneously, and <I>Methanosarcina</I> and <I>Methanobacterium</I> were enriched. However, the reactor fed with glucose was prone to acidification because volatile fatty acids accumulated in the medium, which inhibited methane synthesis. <I>Geobacter</I> was dominant in the reactor fed with ethanol and 45% of genes encoding pili synthesis were attributable to <I>Geobacter</I>, indicating that direct interspecies electron transfer may be a possible mechanism during syntrophic methanogenesis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Metagenomic analysis qualifies the effect of C-source on methanogenesis. </LI> <LI> Aceticlastic methanogenesis dominates when using tryptone or acetate/propionate. </LI> <LI> Aceticlastic and hydrogenotrophic methanogenesis occur with glucose or ethanol. </LI> <LI> Syntrophic methanogenesis via DIET by <I>Geobacter</I> present with ethanol. </LI> </UL> </P>