Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education, China), School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, China.
School of Environment Science and Engineering, Suzhou University of Science and Technology, Suzhou, 215002, China.
Environ Res. 2021 Sep;200:111390. doi: 10.1016/j.envres.2021.111390. Epub 2021 May 28.
In this work, a novel nitrate (NO) reduction pathway by anaerobic ammonium oxidation (anammox) biomass was firstly discovered with the intracellular carbon sources as the only electron donors. And the possible reaction mechanism was deduced to be intracellular dissimilatory nitrate reduction to ammonium (DNRA) pathway according to the experimental results. In batch experiments, without any external electron donors, NO-N (about 50 mg/L) was reduced to N within 48 h, and a small amount of NO-N was detected (the maximum of 2 mg/L) with the anammox biomass concentration of 4400 mg/L. Acetylene (4.46 mmol/L) addition resulted in obvious NH accumulation during NO degradation by anammox biomass, since acetylene mainly interfered in hydrazine (NH) generation from NH and NO. Without HCO addition, the NO-N degradation rate was slower than that with HCO addition. Simultaneously, glycogen contents inside anammox biomass decreased to 133.22 ± 1.21 mg/g VSS and 129.79 ± 1.21 mg/g VSS with and without HCO, respectively, from 142.20 ± 0.61 mg/g VSS. In the long-term experiment, anammox biomass stably degraded NO-N without external electron donors addition, and the maximum removal efficiency of NO-N reached 55.4%. The above results indicated the anammox bacteria utilized the DNRA pathway to reduce NO to NO and further NH, then normal anammox metabolism would continue to convert the produced NO and NH to N. The intracellular stored carbon sources (e.g., glycogen) were supposed to be electron donors for NO degradation. This capability would enhance the viability and living space of anammox bacteria in different natural ecosystems, and make it plausible that complete nitrogen removal could be implemented only by the anammox process.
在这项工作中，首次发现了一种新型的硝酸盐（NO）还原途径，即厌氧氨氧化（anammox）生物量以细胞内碳源作为唯一电子供体。根据实验结果，推断可能的反应机制为细胞内异化硝酸盐还原为铵（DNRA）途径。在批式实验中，在没有任何外加电子供体的情况下，48 小时内将约 50mg/L 的 NO-N 还原为 N，并且在 4400mg/L 的 anammox 生物量浓度下检测到少量的 NO-N（最大 2mg/L）。添加乙炔（4.46mmol/L）会导致 anammox 生物量在降解 NO 时明显积累 NH，因为乙炔主要干扰 NH 和 NO 生成肼（NH）。没有 HCO 添加时，NO-N 的降解速率比有 HCO 添加时慢。同时，在没有 HCO 添加的情况下，anammox 生物量中的糖原含量分别从 142.20±0.61mg/g VSS 下降至 133.22±1.21mg/g VSS 和 129.79±1.21mg/g VSS，而在有 HCO 添加的情况下，糖原含量从 142.20±0.61mg/g VSS 下降至 133.22±1.21mg/g VSS 和 129.79±1.21mg/g VSS。在长期实验中，anammox 生物量在没有外加电子供体的情况下稳定地降解 NO-N，最大的 NO-N 去除效率达到 55.4%。上述结果表明，anammox 细菌利用 DNRA 途径将 NO 还原为 NO 和进一步的 NH，然后正常的 anammox 代谢将继续将产生的 NO 和 NH 转化为 N。细胞内储存的碳源（例如糖原）可能是 NO 降解的电子供体。这种能力增强了 anammox 细菌在不同自然生态系统中的生存能力和生存空间，使得仅通过 anammox 过程实现完全脱氮成为可能。
