초록
<P>This study proposes an innovative setup composed by two stage reactors to achieve biogas upgrading coupling the CO<SUB>2</SUB> in the biogas with external H<SUB>2</SUB> and subsequent conversion into CH<SUB>4</SUB> by hydrogenotrophic methanogenesis. In this configuration, the biogas produced in the first reactor was transferred to the second one, where H<SUB>2</SUB> was injected. This configuration was tested at both mesophilic and thermophilic conditions. After H<SUB>2</SUB> addition, the produced biogas was upgraded to average CH<SUB>4</SUB> content of 89% in the mesophilic reactor and 85% in the thermophilic. At thermophilic conditions, a higher efficiency of CH<SUB>4</SUB> production and CO<SUB>2</SUB> conversion was recorded. The consequent increase of pH did not inhibit the process indicating adaptation of microorganisms to higher pH levels. The effects of H<SUB>2</SUB> on the microbial community were studied using high-throughput Illumina random sequences and full-length 16S rRNA genes extracted from the total sequences. The relative abundance of archaeal community markedly increased upon H<SUB>2</SUB> addition with <I>Methanoculleus</I> as dominant genus. The increase of hydrogenotrophic methanogens and syntrophic <I>Desulfovibrio</I> and the decrease of aceticlastic methanogens indicate a H<SUB>2</SUB>-mediated shift toward the hydrogenotrophic pathway enhancing biogas upgrading. Moreover, <I>Thermoanaerobacteraceae</I> were likely involved in syntrophic acetate oxidation with hydrogenotrophic methanogens in absence of aceticlastic methanogenesis.</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-20/acs.est.5b03451/production/images/medium/es-2015-03451n_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es5b03451'>ACS Electronic Supporting Info</A></P>