title: Functionally redundant but dissimilar microbial communities within biogas reactors treating maize silage in co-fermentation with sugar beet silage.
abstract: Numerous observations indicate a high flexibility of microbial communities in different biogas reactors during anaerobic digestion. Here, we describe the functional redundancy and structural changes of involved microbial communities in four lab-scale continuously stirred tank reactors (CSTRs, 39°C, 12 L volume) supplied with different mixtures of maize silage (MS) and sugar beet silage (SBS) over 80 days. Continuously stirred tank reactors were fed with mixtures of MS and SBS in volatile solid ratios of 1:0 (Continuous Fermenter (CF) 1), 6:1 (CF2), 3:1 (CF3), 1:3 (CF4) with equal organic loading rates (OLR 1.25 kgVS m(-3)  d(-1) ) and showed similar biogas production rates in all reactors. The compositions of bacterial and archaeal communities were analysed by 454 amplicon sequencing approach based on 16S rRNA genes. Both bacterial and archaeal communities shifted with increasing amounts of SBS. Especially pronounced were changes in the archaeal composition towards Methanosarcina with increasing proportion of SBS, while Methanosaeta declined simultaneously. Compositional shifts within the microbial communities did not influence the respective biogas production rates indicating that these communities adapted to environmental conditions induced by different feedstock mixtures. The diverse microbial communities optimized their metabolism in a way that ensured efficient biogas production.
authors.affiliation: Institute of Microbiology and Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
authors.forename: Susanne G
authors.initials: SG
authors.lastname: Langer
authors.affiliation: Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
authors.forename: Sharif
authors.initials: S
authors.lastname: Ahmed
authors.affiliation: Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Einfalt
authors.affiliation: Institute of Microbiology and Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
authors.forename: Frank R
authors.initials: FR
authors.lastname: Bengelsdorf
authors.affiliation: Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
authors.forename: Marian
authors.initials: M
authors.lastname: Kazda
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001105:Archaea / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D027461:Beta vulgaris / Q000378:metabolism*; D056804:Biofuels; D019149:Bioreactors / Q000382:microbiology*; D058448:Biota; D019641:DNA, Archaeal / Q000737:chemistry / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005285:Fermentation; D008969:Molecular Sequence Data; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012820:Silage / Q000382:microbiology; D013696:Temperature; D003313:Zea mays / Q000378:metabolism*
chemical_list: D056804:Biofuels; D019641:DNA, Archaeal; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S