title: Methanogenic pathway and community structure in a thermophilic anaerobic digestion process of organic solid waste.
abstract: The methanogenic pathway and microbial community in a thermophilic anaerobic digestion process of organic solid waste were investigated in a continuous-flow stirred-tank reactor using artificial garbage slurry as a feedstock. The decomposition pathway of acetate, a significant precursor of CH(4) and a key intermediate metabolite in the anaerobic digestion process, was analyzed by using stable isotopes. A tracer experiment using (13)C-labeled acetate revealed that approximately 80% of the acetate was decomposed via a non-aceticlastic oxidative pathway, whereas the remainder was converted to methane via an aceticlastic pathway. Archaeal 16S rRNA analyses demonstrated that the hydrogenotrophic methanogens Methanoculleus spp. accounted for >90% of detected methanogens, and the aceticlastic methanogens Methanosarcina spp. were the minor constituents. The clone library targeting bacterial 16S rRNA indicated the predominance of the novel Thermotogales bacterium (relative abundance: ~53%), which is related to anaerobic acetate oxidizer Thermotoga lettingae TMO, although the sequence similarity was low. Uncultured bacteria that phylogenetically belong to municipal solid waste cluster I were also predominant in the microflora (~30%). These results imply that the microbial community in the thermophilic degrading process of organic solid waste consists exclusively of unidentified bacteria, which efficiently remove acetate through a non-aceticlastic oxidative pathway.
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sasaki
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hori
authors.forename: Shin
authors.initials: S
authors.lastname: Haruta
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Ueno
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ishii
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Igarashi
mesh_terms: D000085:Acetates / Q000378:metabolism*; D000693:Anaerobiosis; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology*; D002247:Carbon Isotopes / Q000378:metabolism; D019605:Euryarchaeota / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D010802:Phylogeny; D019642:RNA, Archaeal / Q000235:genetics; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage / Q000382:microbiology*
chemical_list: D000085:Acetates; D002247:Carbon Isotopes; D019642:RNA, Archaeal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D008697:Methane