title: Identification of key nitrous oxide production pathways in aerobic partial nitrifying granules.
abstract: The identification of the key nitrous oxide (N2O) production pathways is important to establish a strategy to mitigate N2O emission. In this study, we combined real-time gas-monitoring analysis, (15)N stable isotope analysis, denitrification functional gene transcriptome analysis and microscale N2O concentration measurements to identify the main N2O producers in a partial nitrification (PN) aerobic granule reactor, which was fed with ammonium and acetate. Our results suggest that heterotrophic denitrification was the main contributor to N2O production in our PN aerobic granule reactor. The heterotrophic denitrifiers were probably related to Rhodocyclales bacteria, although different types of bacteria were active in the initial and latter stages of the PN reaction cycles, most likely in response to the presence of acetate. Hydroxylamine oxidation and nitrifier denitrification occurred, but their contribution to N2O emission was relatively small (20-30%) compared with heterotrophic denitrification. Our approach can be useful to quantitatively examine the relative contributions of the three pathways (hydroxylamine oxidation, nitrifier denitrification and heterotrophic denitrification) to N2O emission in mixed microbial populations.
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ishii
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Song
authors.forename: Lashitha
authors.initials: L
authors.lastname: Rathnayake
authors.forename: Azzaya
authors.initials: A
authors.lastname: Tumendelger
authors.forename: Hisashi
authors.initials: H
authors.lastname: Satoh
authors.forename: Sakae
authors.initials: S
authors.lastname: Toyoda
authors.forename: Naohiro
authors.initials: N
authors.lastname: Yoshida
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okabe
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology*; D058440:Denitrification / Q000235:genetics; D052836:Heterotrophic Processes; D019811:Hydroxylamine / Q000378:metabolism; D058465:Nitrification; D009609:Nitrous Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D059467:Transcriptome
chemical_list: D019811:Hydroxylamine; D009609:Nitrous Oxide