title: A robust nitrifying community in a bioreactor at 50 °C opens up the path for thermophilic nitrogen removal.
abstract: The increasing production of nitrogen-containing fertilizers is crucial to meet the global food demand, yet high losses of reactive nitrogen associated with the food production/consumption chain progressively deteriorate the natural environment. Currently, mesophilic nitrogen-removing microbes eliminate nitrogen from wastewaters. Although thermophilic nitrifiers have been separately enriched from natural environments, no bioreactors are described that couple these processes for the treatment of nitrogen in hot wastewaters. Samples from composting facilities were used as inoculum for the batch-wise enrichment of thermophilic nitrifiers (350 days). Subsequently, the enrichments were transferred to a bioreactor to obtain a stable, high-rate nitrifying process (560 days). The community contained up to 17% ammonia-oxidizing archaea (AOAs) closely related to 'Candidatus Nitrososphaera gargensis', and 25% nitrite-oxidizing bacteria (NOBs) related to Nitrospira calida. Incorporation of (13)C-derived bicarbonate into the respective characteristic membrane lipids during nitrification supported their activity as autotrophs. Specific activities up to 198±10 and 894±81 mg N g(-1) VSS per day for AOAs and NOBs were measured, where NOBs were 33% more sensitive to free ammonia. The NOBs were extremely sensitive to free nitrous acid, whereas the AOAs could only be inhibited by high nitrite concentrations, independent of the free nitrous acid concentration. The observed difference in product/substrate inhibition could facilitate the development of NOB inhibition strategies to achieve more cost-effective processes such as deammonification. This study describes the enrichment of autotrophic thermophilic nitrifiers from a nutrient-rich environment and the successful operation of a thermophilic nitrifying bioreactor for the first time, facilitating opportunities for thermophilic nitrogen removal biotechnology.
authors.affiliation: Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Gent, Belgium.
authors.forename: Emilie Np
authors.initials: EN
authors.lastname: Courtens
authors.affiliation: Biocenter Klein Flottbek and Department of Microbiology and Biotechnology, University of Hamburg, Hamburg, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Spieck
authors.affiliation: Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Gent, Belgium.
authors.forename: Ramiro
authors.initials: R
authors.lastname: Vilchez-Vargas
authors.affiliation: Isotope Bioscience Laboratory, Ghent University, Gent, Belgium.
authors.forename: Samuel
authors.initials: S
authors.lastname: Bodé
authors.affiliation: Isotope Bioscience Laboratory, Ghent University, Gent, Belgium.
authors.forename: Pascal
authors.initials: P
authors.lastname: Boeckx
authors.affiliation: Royal Netherlands Institute for Sea Research (NIOZ), Texel, The Netherlands.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schouten
authors.affiliation: Microbial Interactions and Processes Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany.
authors.forename: Ruy
authors.initials: R
authors.lastname: Jauregui
authors.affiliation: Microbial Interactions and Processes Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany.
authors.forename: Dietmar H
authors.initials: DH
authors.lastname: Pieper
authors.affiliation: Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Gent, Belgium.|Research Group of Sustainable Energy, Air and Water Technology, University of Antwerp, Antwerpen, Belgium.
authors.forename: Siegfried E
authors.initials: SE
authors.lastname: Vlaeminck
authors.affiliation: Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Gent, Belgium.
authors.forename: Nico
authors.initials: N
authors.lastname: Boon
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001105:Archaea / Q000378:metabolism*; D052818:Autotrophic Processes; D001419:Bacteria / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005308:Fertilizers; D059014:High-Throughput Nucleotide Sequencing; D006358:Hot Temperature; D058465:Nitrification; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D062065:Wastewater / Q000737:chemistry*
chemical_list: D000641:Ammonia; D004275:DNA, Ribosomal; D005308:Fertilizers; D009573:Nitrites; D009584:Nitrogen; D062065:Wastewater