Abstract
Mixed or pure cultures can be used for biomethanation of hydrogen. Sodium 2-bromoethanesulfonate (BES) is an inhibitor of methanogenesis used to investigate competing reactions like homoacetogenesis in mixed cultures. To understand the effect of BES on the hydrogenotrophic metabolism in a biomethanation process, anaerobic granules from a wastewater treatment plant, a hydrogenotrophic enrichment culture, and pure cultures of Methanococcus maripaludis and Methanobacterium formicicum were incubated under H2/CO2 headspace in the presence or absence of BES, and the turnover of H2, CO2, CH4, formate and acetate was analyzed. Anaerobic granules produced the highest amount of formate after 24 h of incubation in the presence of BES. Treating the enrichment culture with BES led to the accumulation of formate. M. maripaludis produced more formate than M. formicicum when treated with BES. The non-inhibited methanogenic communities produced small amounts of formate whereas the pure cultures did not. The highest amount of acetate was produced by the anaerobic granules concomitantly with formate consumption. These results indicate that formate is an important intermediate of hydrogenotrophic metabolism accumulating upon methanogenesis inhibition.
Highlights
The pure cultures tested in this study showed similar methane production rates as reported in a recent study screening a massive number of methanogenic strains [10]
We have previously investigated the community composition of anaerobic granules sampled from the same wastewater treatment plant and the hydrogenotrophic enrichment culture
This study showed with pure methanogenic strains, a highly enriched hydrogenotrophic community, and anaerobic granules from a wastewater treatment system that formate is an important intermediate of H2 /CO2 metabolism during methanogenesis inhibition with
Summary
Methanation of hydrogen can be a thermochemical or biological process (biomethanation of hydrogen) [1]. Biological biogas upgrading based on hydrogen biomethanation makes use of in situ (biocatalysis in the main anaerobic digester), ex situ (biocatalysis in a reactor other than the main anaerobic digester) or hybrid (combining in situ and ex situ) concepts [4,7,8]. Biomethanation of hydrogen converts the CO2 content of biogas into additional methane via the CO2 -reductive pathway of hydrogenotrophic methanogens. The conversion of hydrogen and CO2 to methane is carried out by pure cultures of hydrogenotrophic methanogens [9,10] or mixed cultures [4]. Mixed cultures have certain economic and process advantages over pure cultures [4,11]. Competing reactions, such as homoacetogenesis, are difficult to control. When performing biomethanation of hydrogen with mixed cultures, hydrogenotrophic methanogenesis (Equation (1)), homoacetogenesis (Equation (2)), syntrophic acetate oxidation (SAO) (Equation (3)), and
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