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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Energy Res. | doi: 10.3389/fenrg.2019.00132

Microbial community rearrangements in power-to-biomethane reactors employing mesophilic biogas digestate

Norbert Ács1,  Márk Szuhaj1, Zoltán Bagi1,  Gergely Maroti2,  Gábor Rákhely1 and  Kornél L. Kovács1*
  • 1Department of Biotechnology, University of Szeged, Hungary
  • 2Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Hungary

The biological conversion of hydrogen (H2) and carbon dioxide (CO2) to methane (CH4), is accomplished by the hydrogenotrophic methanogens (HM). HMs are difficult to cultivate in pure culture, but they are readily available in the mixed culture of effluents from the anaerobic degradation of organic matter, i.e. the fermentation effluent of biogas plants. The rate-limiting step in the work of CH4-forming microbial communities is the low solubility of H2 in the aqueous environment. In our approach, the simple fed-batch fermentation technique was selected to supply the gaseous substrates for the microbial community at laboratory scale and mesophilic temperature. Periodically withdrawn samples were analyzed for process parameters and the microbial communities were studied using Terminal Restriction Fragment Length Polymorphism (T-RFLP) of the mcrA gene and Ion Torrent whole metagenome DNA sequencing. The metagenome data were evaluated by both read-based and genome-centric bioinformatics tools. The rearrangements in the mixed microbial communities, triggered by switching the operating conditions to biological power-to-biomethane (bio-P2M), have been established. The production rates were 6.30 mL CH4 L-1 h-1 during the acclimation phase and 9.21 mL CH4 L-1 h-1 by the fully adapted community, respectively. The diversity of the anaerobic microbiota decreased as the bio-P2M process progressed. Feeding the community with H2 apparently promoted the abundance of several genera, in particular Candidatus Cloacimonas and Herbinix. The diversity of the Archaea community decreased considerably upon daily feeding with H2 and CO2. The predominant Archea genus was Methanobacterium in every reactor, Methanothrix persisted for the first 4 weeks, while the initially less abundant genus Methanoculleus gained advantage during the adaptation to the sustained bio-P2M process. The accumulation of acetate indicated a strong involvement of homoacetogenic bacteria.

Keywords: T-RFLP, biological power-to-methane, mcrA, whole genome DNA sequencing, Hydrogen, Carbon Dioxide, acetate

Received: 22 Jan 2019; Accepted: 04 Nov 2019.

Copyright: © 2019 Ács, Szuhaj, Bagi, Maroti, Rákhely and Kovács. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Kornél L. Kovács, Department of Biotechnology, University of Szeged, Szeged, Hungary, kovacs.kornel@bio.u-szeged.hu