Otte S, Grobben N G, Robertson L A, Jetten M S, Kuenen J G
Kluyver Laboratory for Biotechnology, Delft University of Technology, The Netherlands.
Appl Environ Microbiol. 1996 Jul;62(7):2421-6. doi: 10.1128/aem.62.7.2421-2426.1996.
Nitrous oxide can be a harmful by-product in nitrogen removal from wastewater. Since wastewater treatment systems operate under different aeration regimens, the influence of different oxygen concentrations and oxygen fluctuations on denitrification was studied. Continuous cultures of Alcaligenes faecalis TUD produced N2O under anaerobic as well as aerobic conditions. Below a dissolved oxygen concentration of 5% air saturation, the relatively highest N2O production was observed. Under these conditions, significant activities of nitrite reductase could be measured. After transition from aerobic to anaerobic conditions, there was insufficient nitrite reductase present to sustain growth and the culture began to wash out. After 20 h, nitrite reductase became detectable and the culture started to recover. Nitrous oxide reductase became measurable only after 27 h, suggesting sequential induction of the denitrification reductases, causing the transient accumulation of N2O. After transition from anaerobic conditions to aerobic conditions, nitrite reduction continued (at a lower rate) for several hours. N2O reduction appeared to stop immediately after the switch, indicating inhibition of nitrous oxide reductase, resulting in high N2O emissions (maximum, 1.4 mmol liter-1 h-1). The nitrite reductase was not inactivated by oxygen, but its synthesis was repressed. A half-life of 16 to 22 h for nitrite reductase under these conditions was calculated. In a dynamic aerobic-anaerobic culture of A. faecalis, a semisteady state in which most of the N2O production took place after the transition from anaerobic to aerobic conditions was obtained. The nitrite consumption rate in this culture was equal to that in an anaerobic culture (0.95 and 0.92 mmol liter-1 h-1, respectively), but the production of N2O was higher in the dynamic culture (28 and 26% of nitrite consumption, respectively).
一氧化二氮可能是废水脱氮过程中的一种有害副产物。由于废水处理系统在不同的曝气方式下运行，因此研究了不同氧浓度和氧波动对反硝化作用的影响。粪产碱菌TUD的连续培养物在厌氧和好氧条件下均产生N2O。在溶解氧浓度低于5%空气饱和度时，观察到相对最高的N2O产生量。在这些条件下，可以检测到亚硝酸还原酶的显著活性。从好氧条件转变为厌氧条件后，亚硝酸还原酶不足以维持生长，培养物开始被冲刷掉。20小时后，亚硝酸还原酶变得可检测到，培养物开始恢复。一氧化二氮还原酶仅在27小时后才可检测到，这表明反硝化还原酶是顺序诱导的，导致N2O的瞬时积累。从厌氧条件转变为好氧条件后，亚硝酸盐还原持续（以较低速率）数小时。转换后N2O还原似乎立即停止，表明一氧化二氮还原酶受到抑制，导致高N2O排放（最高为1.4 mmol·L-1·h-1）。亚硝酸还原酶未被氧灭活，但其合成受到抑制。计算出在这些条件下亚硝酸还原酶的半衰期为16至22小时。在粪产碱菌的动态好氧-厌氧培养中，获得了一种半稳态，其中大部分N2O产生发生在从厌氧条件转变为好氧条件之后。该培养物中亚硝酸盐消耗速率与厌氧培养中的消耗速率相等（分别为0.95和0.92 mmol·L-1·h-1），但动态培养中N2O的产生量更高（分别为亚硝酸盐消耗量的28%和26%）。
