短程硝化中羟胺代谢对N2O排放的贡献及微生物驱动机制

Partial nitrification is a controlled process from ammonia oxidation to nitrite accumulation stage. It was observed that partial nitrification will produce higher concentration of N2O than traditional nitrification/denitrification-based N-removal. Therefore, it is of great practical significance to study the metabolism of N2O emission and the control pathway. Hydroxylamine (NH2OH) is an intermediate in the biological oxidation of ammonia to nitrite by ammonia-oxidizing bacteria (AOB). There is a direct relationship between hydroxylamine accumulation and the production of N2O. However, the related research concerning to hydroxylamine metabolism is insufficient. .In this proposal, we will analysis the metabolism process of hydroxylamine in partial nitrification system using 15N and 18O stable isotope tracer technology combined with nitrogen metabolism flux methods. The dynamic change process of hydroxylamine in partial nitrification process and the distribution of metabolites in the inorganic nitrogen metabolism network will be analyzed in details. On the other hand，the microbial community structure and the key enzyme gene concerning to nitrogen metabolism will be studied. Through the works above, we want to clarify the contribution of hydroxylamine metabolism to N2O emissions in partial nitrification comprehensively, and find the relationship of microbial population structure and gene expression within the metabolism of hydroxylamine and N2O emission.

短程硝化是将氨氧化控制在亚硝化阶段的硝化过程，短程硝化工艺带来的高N2O释放问题受到日益关注，研究短程硝化中N2O的代谢通路及其减量控制具有重要的现实意义。羟胺是硝化过程中的重要中间代谢产物，其代谢方式直接影响着N2O的产生，但相关研究还不够深入。本项目围绕短程硝化反应器中的羟胺代谢过程，用15N、18O稳定同位素示踪技术结合氮代谢通量方法，分析、定量检测短程硝化工艺中羟胺的动态变化及其代谢产物在无机氮代谢网络中的分布情况，综合评估羟胺代谢对短程硝化中N2O排放的贡献；结合反应器中微生物群落分析及氮代谢相关基因表达量研究，探索微生物群落结构和基因表达与羟胺代谢及N2O排放的耦合关系，阐明羟胺代谢的微生物驱动机制，为实现N2O减量控制提供理论依据。

短程硝化是将氨氧化控制在亚硝化阶段的硝化过程，短程硝化工艺带来的高N2O释放问题 受到日益关注，研究短程硝化中N2O的代谢通路及其减量控制具有重要的现实意义。羟胺是硝化过程中的重要中间代谢产物，其代谢方式直接影响着N2O的产生，但相关研究还不够深入。本项目围绕短程硝化反应器中的羟胺代谢过程，用15N、18O稳定同位素示踪技术结合氮代谢通量方法，分析、定量检测短程硝化工艺中羟胺的动态变化及其代谢产物在无机氮代谢网络中的分布情况，综合评估羟胺代谢对短程硝化中N2O排放的贡献；结合反应器中微生物群落分析及氮代谢相关基因表达量研究，探索微生物群落结构和基因表达与羟胺代谢及N2O排放的耦合关系，阐明羟胺代谢的微生物驱动机制，为实现N2O减量控制提供理论依据。我们构建了小型短程硝化反应器，综合评估了羟胺代谢对短程硝化中N2O排放的贡献，发现气态N2O的释放量约占总氮量的6.3%，羟胺氧化对N2O产生的贡献率大于59%；结合微生物群落结构分析和宏基因组研究，探索了反应器中微生物群落结构和基因表达与羟胺代谢及N2O排放的耦合关系，推导了N2O释放的微生物驱动机制；从反应器中发现一类可以将氨经过羟胺直接转化为氮气的新颖氮代谢菌株，从这类菌中克隆到参与氨氧化过程的新基因簇(dnf)。Alcaligenes属的成员广泛分布在各种环境中，对氮循环具有重要贡献，对反应器中这类菌的强化培养，有望从源头减少N2O的产生。