title: Microbial community changes in methanogenic granules during the transition from mesophilic to thermophilic conditions.
abstract: Upflow anaerobic sludge blanket (UASB) reactor is one of the most applied technologies for various high-strength wastewater treatments. The present study analysed the microbial community changes in UASB granules during the transition from mesophilic to thermophilic conditions. Dynamicity of microbial community in granules was analysed using high-throughput sequencing of 16S ribosomal RNA gene amplicons, and the results showed that the temperature strictly determines the diversity of the microbial consortium. It was demonstrated that most of the microbes which were present in the initial mesophilic community were not found in the granules after the transition to thermophilic conditions. More specifically, only members from family Anaerolinaceae managed to tolerate the temperature change and contributed in maintaining the physical integrity of granular structure. On the contrary, new hydrolytic and fermentative bacteria were quickly replacing the old members in the community. A direct result from this abrupt change in the microbial diversity was the accumulation of volatile fatty acids and the concomitant pH drop in the reactor inhibiting the overall anaerobic digestion process. Nevertheless, by maintaining deliberately the pH levels at values higher than 6.5, a methanogen belonging to Methanoculleus genus emerged in the community enhancing the methane production.
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, Bld 113, 2800, Kgs. Lyngby, Denmark.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, Bld 113, 2800, Kgs. Lyngby, Denmark. panak@env.dtu.dk.
authors.forename: Panagiotis G
authors.initials: PG
authors.lastname: Kougias
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, Bld 113, 2800, Kgs. Lyngby, Denmark.|Department of Agronomy, Food, Natural resources, Animal and Environment (DAFNAE), viale dell'Università 16, 35020, Legnaro, Padova, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Treu
authors.affiliation: Department of Biology, University of Padova, Via U. Bassi 58/b, 35121, Padova, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Campanaro
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, Bld 113, 2800, Kgs. Lyngby, Denmark.
authors.forename: Irini
authors.initials: I
authors.lastname: Angelidaki
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000235:genetics; D019149:Bioreactors; D004269:DNA, Bacterial / Q000235:genetics; D014644:Genetic Variation; D059014:High-Throughput Nucleotide Sequencing; D008697:Methane / Q000378:metabolism*; D059013:Microbial Consortia / Q000235:genetics* / Q000502:physiology; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S; D012722:Sewage / Q000382:microbiology*; D013696:Temperature; D014865:Waste Disposal, Fluid
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D008697:Methane
keywords: 16S rRNA gene; Granule structure; Microbial community; Temperature; UASB