초록
<P>The advent of renewable energy conversion systems exacerbates the existing issue of intermittent excess power. Microbial electrosynthesis can use this power to capture CO<SUB>2</SUB> and produce multicarbon compounds as a form of energy storage. As catalysts, microbial populations can be used, provided side reactions such as methanogenesis are avoided. Here a simple but effective approach is presented based on enrichment of a robust microbial community via several culture transfers with H<SUB>2</SUB>:CO<SUB>2</SUB> conditions. This culture produced acetate at a concentration of 1.29 ± 0.15 g L<SUP>–1</SUP> (maximum up to 1.5 g L<SUP>–1</SUP>; 25 mM) from CO<SUB>2</SUB> at a fixed current of −5 Am<SUP>–2</SUP> in fed-batch bioelectrochemical reactors at high N<SUB>2</SUB>:CO<SUB>2</SUB> flow rates. Continuous supply of reducing equivalents enabled acetate production at a rate of 19 ± 2 gm<SUP>–2</SUP>d<SUP>–1</SUP> (projected cathode area) in several independent experiments. This is a considerably high rate compared with other unmodified carbon-based cathodes. 58 ± 5% of the electrons was recovered in acetate, whereas 30 ± 10% of the electrons was recovered in H<SUB>2</SUB> as a secondary product. The bioproduction was most likely H<SUB>2</SUB> based; however, electrochemical, confocal microscopy, and community analyses of the cathodes suggested the possible involvement of the cathodic biofilm. Together, the enrichment approach and galvanostatic operation enabled instant start-up of the electrosynthesis process and reproducible acetate production profiles.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2015/esthag.2015.49.issue-14/es506149d/production/images/medium/es-2014-06149d_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es506149d'>ACS Electronic Supporting Info</A></P>