초록
<P>Methane (CH<SUB>4</SUB>)-producing bioelectrochemical systems (BES) are an attractive way to store excess renewable electricity and captured CO<SUB>2</SUB>. Studies have suggested that methanogenesis via direct electron uptake from a biocathode is more energetically efficient than hydrogenotrophic methanogenesis. However, mechanisms and key microorganisms involved in direct electron uptake remain unclear, primarily because of H<SUB>2</SUB> produced by bacteria or extracellular hydrogenases in the system. In an attempt to minimize biological H<SUB>2</SUB> production and enrich for methanogens that could efficiently convert electrons from the cathode surface to CH<SUB>4</SUB>, cathode chambers were pretreated with antibiotics targeting bacteria. We found that antibiotics pretreatment effectively reduced the proportion of H<SUB>2</SUB>-producing bacteria and H<SUB>2</SUB>-utilizing methanogens associated with the biocathode biofilm, and significantly promoted growth of acetoclastic methanogens from the genera <I>Methanosarcina</I> and <I>Methanosaeta</I>, several of which are known to participate in direct interspecies electron transfer. This shift in microbial community structure corresponded with 14%–36% higher cathode capture efficiencies. These results suggest that suppression of H<SUB>2</SUB> production by antibiotics pretreatment could be a promising way to enrich for methanogens that can efficiently transform electrons from a biocathode into CH<SUB>4</SUB>.</P><P>Bioelectrochemical CH<SUB>4</SUB> production could be used to store excess renewable electricity and captured CO<SUB>2</SUB>, providing a sustainable substitute for limited natural gas.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ascecg/2017/ascecg.2017.5.issue-10/acssuschemeng.7b00923/production/images/medium/sc-2017-00923z_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/sc7b00923'>ACS Electronic Supporting Info</A></P>