School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, No.13 Yanta road, Xi'an 710055, PR China; Key Lab of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, No.13 Yanta road, Xi'an 710055, PR China; Shaanxi Key Lab of Environmental Engineering, Xi'an 710055, PR China.
School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, No.13 Yanta road, Xi'an 710055, PR China; Key Lab of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, No.13 Yanta road, Xi'an 710055, PR China; Shaanxi Key Lab of Environmental Engineering, Xi'an 710055, PR China.
Sci Total Environ. 2022 Nov 10;846:157513. doi: 10.1016/j.scitotenv.2022.157513. Epub 2022 Jul 21.
This study analyzed the activities of all denitrifying enzymes involved in the denitrification process under different organic loads in a continuously operating sequencing batch reactor (SBR), to reveal how the denitrifying enzymes performed while the denitrifying bacteria facing changes in organic load, and leading to nitrous oxide (NO) production by fine-tuning enzyme activities. Results show that the activities of nitrate reductase (Nar), nitrite reductase (Nir), nitric oxide reductase (Nor) and nitrous oxide reductase (NOR) increased with the increase of organic loads, and the increase of the activity of different enzymes promoted by the organic load increase were as Nar > Nir > Nor > NOR. Compared with the Nar and Nir, the catalytic processes of the Nor and NOR were more susceptible to the influence of the substrate concentration and the content of internal and external carbon sources. The Nor usually maintained "excess" catalytic activity to ensure the smooth reduction of nitric oxide when the electron donor and substrate were sufficient. Otherwise, it reduced to a relatively lower catalytic activity and remained stable. The activities of the NOR were generally weaker than that of other denitrifying enzymes. More NO was produced in the period feeding with low organic loads (COD/NO-N ≤ 4.9). The mechanism of the enzyme activities (Nor and NOR) regulating the total concentrations of NO was clarified. When the organic load was relatively low (COD/NO-N ≤ 2.5), the NOR activity was inhibited due to its inability to acquire enough electrons, resulting the production of NO. When the organic load was moderate (2.5 < COD/NO-N ≤ 4.9), the NOR activity was lower than the Nor activity due to the different activation rates of Nor and NOR by the substrate in bacteria, resulting the production of NO.
本研究分析了连续序批式反应器（SBR）中不同有机负荷下参与反硝化过程的所有反硝化酶的活性，以揭示反硝化细菌在面对有机负荷变化时，如何通过精细调节酶活性来进行反硝化作用，并导致氧化亚氮（NO）的产生。结果表明，硝酸盐还原酶（Nar）、亚硝酸盐还原酶（Nir）、一氧化氮还原酶（Nor）和一氧化二氮还原酶（NOR）的活性随着有机负荷的增加而增加，不同酶活性增加的原因是Nar>Nir>Nor>NOR。与 Nar 和 Nir 相比，Nor 和 NOR 的催化过程更容易受到底物浓度和内外碳源含量的影响。当电子供体和底物充足时，Nor 通常保持“过剩”的催化活性，以确保一氧化氮的顺利还原。否则，它会降低到相对较低的催化活性并保持稳定。NOR 的活性通常比其他反硝化酶弱。在低有机负荷（COD/NO-N ≤ 4.9）下进料时，会产生更多的 NO。阐明了酶活性（Nor 和 NOR）调节总 NO 浓度的机制。当有机负荷较低（COD/NO-N ≤ 2.5）时，由于 NOR 无法获得足够的电子，其活性受到抑制，导致 NO 的产生。当有机负荷适中（2.5 < COD/NO-N ≤ 4.9）时，由于 Nor 和 NOR 被细菌中的底物以不同的速率激活，NOR 的活性低于 Nor 的活性，导致 NO 的产生。
