title: Noteworthy Facts about a Methane-Producing Microbial Community Processing Acidic Effluent from Sugar Beet Molasses Fermentation.
abstract: Anaerobic digestion is a complex process involving hydrolysis, acidogenesis, acetogenesis and methanogenesis. The separation of the hydrogen-yielding (dark fermentation) and methane-yielding steps under controlled conditions permits the production of hydrogen and methane from biomass. The characterization of microbial communities developed in bioreactors is crucial for the understanding and optimization of fermentation processes. Previously we developed an effective system for hydrogen production based on long-term continuous microbial cultures grown on sugar beet molasses. Here, the acidic effluent from molasses fermentation was used as the substrate for methanogenesis in an upflow anaerobic sludge blanket bioreactor. This study focused on the molecular analysis of the methane-yielding community processing the non-gaseous products of molasses fermentation. The substrate for methanogenesis produces conditions that favor the hydrogenotrophic pathway of methane synthesis. Methane production results from syntrophic metabolism whose key process is hydrogen transfer between bacteria and methanogenic Archaea. High-throughput 454 pyrosequencing of total DNA isolated from the methanogenic microbial community and bioinformatic sequence analysis revealed that the domain Bacteria was dominated by Firmicutes (mainly Clostridia), Bacteroidetes, δ- and γ-Proteobacteria, Cloacimonetes and Spirochaetes. In the domain Archaea, the order Methanomicrobiales was predominant, with Methanoculleus as the most abundant genus. The second and third most abundant members of the Archaeal community were representatives of the Methanomassiliicoccales and the Methanosarcinales. Analysis of the methanogenic sludge by scanning electron microscopy with Energy Dispersive X-ray Spectroscopy and X-ray diffraction showed that it was composed of small highly heterogeneous mineral-rich granules. Mineral components of methanogenic granules probably modulate syntrophic metabolism and methanogenic pathways. A rough functional analysis from shotgun data of the metagenome demonstrated that our knowledge of methanogenesis is poor and/or the enzymes responsible for methane production are highly effective, since despite reasonably good sequencing coverage, the details of the functional potential of the microbial community appeared to be incomplete.
authors.affiliation: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Chojnacka
authors.affiliation: Faculty of Biology, Warsaw University, Warsaw, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Szczęsny
authors.affiliation: Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Warsaw, Poland.
authors.forename: Mieczysław K
authors.initials: MK
authors.lastname: Błaszczyk
authors.affiliation: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Urszula
authors.initials: U
authors.lastname: Zielenkiewicz
authors.affiliation: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Detman
authors.affiliation: Institute of Agricultural and Food Biotechnology, Warsaw, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Salamon
authors.affiliation: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Sikora
mesh_terms: D027461:Beta vulgaris / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D005285:Fermentation; D008697:Methane / Q000096:biosynthesis*; D017018:Methanomicrobiales / Q000378:metabolism*; D008965:Molasses; D012722:Sewage / Q000382:microbiology
chemical_list: D012722:Sewage; D008697:Methane