High nitrite accumulation in hydrogenotrophic denitrification at low temperature: Transcriptional regulation and microbial community succession

• Published in: Water research (Oxford) 2024-10, Vol.263, p.122144, Article 122144
• Main Authors: Zhou, Jianmin, Ding, Lei, Cui, Changzheng, Lindeboom, Ralph E.F.
• Format: Article
• Language: English
• Subjects: Cold Temperature; Denitrification; Denitrifying gene expression; Hydrogenophaga; Hydrogenotrophic denitrification; Low temperature; Nitrate Reductase - genetics; Nitrate Reductase - metabolism; Nitrates - metabolism; Nitrite accumulation; Nitrite Reductases - genetics; Nitrite Reductases - metabolism; Nitrites - metabolism; Paracoccus; Temperature
• ISSN: 0043-1354; 1879-2448; 1879-2448
• DOI: 10.1016/j.watres.2024.122144

•Up to 70 % of the NO3- accumulated as NO2- in hydrogenotrophic system at 15 °C.•Low temperature caused a significant inhibition to the nirS-gene-bearing denitrifiers.•Nitrogen species transformation was determined by denitrification gene expression.•High nitrite accumulation may be related to the enrichment of hydrogenophage spp. High Pressure Hydrogenotrophic Denitrification (HPHD) provided a promising alternative for efficient and clean nitrate removal. In particular, the denitrification rates at low temperature could be compensated by elevated H2 partial pressure. However, nitrite reduction was strongly inhibited while nitrate reduction was barely affected at low temperature. In this study, the nitrate reduction gradually recovered under long-term low temperature stress, while nitrite accumulation increased from 0.1 to 41.0 mg N/L. The activities of the electron transport system (ETS), nitrate reductase (NAR), and nitrite reductase (NIR) decreased by 45.8 %, 27.3 %, and 39.3 %, respectively, as the temperature dropped from 30 °C to 15 °C. Real time quantitative PCR analysis revealed that the denitrifying gene expression rather than gene abundance regulated nitrogen biotransformation. The substantial nitrite accumulation was attributed to the significant up-regulation by 54.7 % of narG gene expression and down-regulation by 73.7 % of nirS gene expression in hydrogenotrophic denitrifiers. In addition, the nirS-gene-bearing denitrifiers were more sensitive to low temperature compared to those bearing nirK gene. The dominant populations shifted from the genera Paracoccus to Hydrogenophaga under long-term low temperature stress. Overall, this study revealed the microbial mechanism of high nitrite accumulation in hydrogenotrophic denitrification at low temperature. [Display omitted]