Intracellular electron competition in response to the oxygen pressure of the aerobic denitrification process in an O2-based membrane biofilm reactor (MBfR) for nitrate removal

This study quantitatively investigated the effect of dissolved oxygen (DO) concentration on aerobic denitrification, and showed the mechanism of aerobic denitrification from the perspective of electron competition by cultivating Pseudomonas stutzeri T13, a typical aerobic denitrifier, in an oxygen-b...

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Published in:The Science of the total environment 2023-06, Vol.875, p.162592-162592, Article 162592
Main Authors: Feng, Liang, Sun, Fei-yun, Yang, Jixian, Cui, Di, Li, Zuo-hua, Pi, Shanshan, Zhao, He-Ping, Li, Ang
Format: Article
Language:English
Subjects:
Aerobic denitrification
Electron competition
Intracellular electron distribution
Oxygen-based membrane biofilm reactor
Pseudomonas stutzeri T13
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Summary:This study quantitatively investigated the effect of dissolved oxygen (DO) concentration on aerobic denitrification, and showed the mechanism of aerobic denitrification from the perspective of electron competition by cultivating Pseudomonas stutzeri T13, a typical aerobic denitrifier, in an oxygen-based membrane biofilm reactor (O2-based MBfR). The experiments showed that when the O2 pressure increased from 2 to 10 psig , the average effluent DO concentration during steady-state phases increased from 0.02 to 4.23 mg/L, and the corresponding mean NO3−-N removal efficiency slightly decreased from 97.2 % to 90.9 %. Compared to the maximum theoretical flux of O2 in various phases, the actual O2 transfer flux increased from a limited status (2.07 e− eq m−2 d−1 at 2 psig) to an excessive status (5.58 e− eq m−2 d−1 at 10 psig). The increase of DO inhibited the electron availability for aerobic denitrification, which decreased from 23.97 % to 11.46 %, accompanying the increased electron availability for aerobic respiration from 15.87 % to 28.36 %. Unlike the napA and norB genes, the expression of the nirS and nosZ genes was significantly affected by DO, with the highest relative fold-changes of 6.5 and 6.13 at 4 psig O2, respectively. The results contribute to clarifying the mechanism of aerobic denitrification from the quantitative perspective of electron distribution and the qualitative perspective of gene expression, which benefits the control and practical application of aerobic denitrification for wastewater treatment. [Display omitted] •Effect of DO concentration on aerobic denitrification was accurately investigated.•Actual O2 consumption was calculated by electron flux analysis.•Electron distribution framework of aerobic denitrification by strain T13 was proposed.•The expression of nirS and nosZ genes were greatly affected by DO concentration.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2023.162592