Dong, Yuji, He, Di, Ren, Zongqiang, Jin, Fei  ORCID: https://orcid.org/0000-0003-0899-7063 and Song, Huiting
2026.
Assimilation-dominated metabolism pathway enables efficient inorganic nitrogen removal and biomass nitrogen accumulation in aerobic-heterotrophic strain R. pyridinivorans B403.
Environmental Research
, 126043.
10.1016/j.envres.2026.126043
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Abstract
Biological treatment is widely used for nitrogen removal from wastewater. The discovery of aerobic-heterotrophic nitrogen removal (AHNR) strains challenged conventional views, yet research has concentrated on nitrification/denitrification while the contribution of ammonia assimilation has received little attention. In this study, the nitrogen metabolism of AHNR strain R. pyridinivorans B403 was characterized. Under optimal conditions (C/N = 11.5, salinity = 0.47%, inoculation amount = 3.0% (v/v)), B403 achieved liquid-phase removal efficiencies of 100%, 86.61%, and 92.24% for NH4+-N, NO3--N, and NO2--N, with maximum rates of 18.77 mg/(L⋅h), 6.30 mg/(L⋅h), and 6.62 mg/(L⋅h), respectively. Nitrogen balance analysis indicated that assimilation was the primary nitrogen metabolism pathway, with 79.20%-89.34% of inorganic nitrogen assimilated into biomass nitrogen and no significant total nitrogen (TN) loss. B403 exhibited high activity of key assimilation enzymes and maintained high nitrogen removal efficiency under nitrification-inhibiting conditions. The genome was annotated with 37 nitrogen metabolism-related genes, including assimilation and nitrate/nitrite reduction pathways, but lacked canonical denitrification gas-production genes. The proposed nitrogen metabolism pathway of B403 is: NH4+-N→ NH2OH → NO2--N ↔ NO3--N → NH4+-N → biomass nitrogen. Bioaugmentation of activated sludge with 5% (v/v) B403 under max 400 mg/L NH4+-N conditions raised mean removal efficiency from 82.33% to 92.53%, significantly reduced NO3--N accumulation and increased sludge protein content. These findings indicate an assimilation-dominated nitrogen metabolism pathway of AHNR strain B403, enabling simultaneous liquid-phase inorganic nitrogen removal with biomass nitrogen accumulation, providing a promising strategy for the efficient treatment of nitrogen-rich wastewater.
| Item Type: | Article |
|---|---|
| Date Type: | Published Online |
| Status: | In Press |
| Schools: | Schools > Engineering |
| Additional Information: | RRS policy applied |
| Publisher: | Elsevier |
| ISSN: | 0013-9351 |
| Date of First Compliant Deposit: | 3 November 2026 |
| Date of Acceptance: | 27 October 2026 |
| Last Modified: | 03 Nov 2026 10:00 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/190565 |
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