Fe3O4对施氏假单胞菌反硝化过程的影响

Effects of Fe3O4 on the denitrification performance of Pseudomonas stutzeri

摘要:

生物反硝化是目前废水深度处理中应用最为广泛的硝酸盐氮处理技术，但该方法一般停留时间较长，在冬季因低温处理效果欠佳，因此有必要开发反硝化强化技术。以施氏假单胞菌Pseudomonas stutzeri为研究对象，考察了不同投加量下Fe3O4对P. stutzeri反硝化过程的影响。结果显示当Fe3O4投加量由0 mg/L增至4 000 mg/L时，硝酸盐氮最大比降解速率由18.0 h–1增加至23.7 h–1，体系中的总蛋白含量以及细菌体内的铁含量显著增加。RT-qPCR和非标记 (Label-free) 定量蛋白组学分析表明，投加4 000 mg/L Fe3O4体系中的P. stutzeri，其反硝化功能基因napA、narJ、nirB、norR、nosZ表达量分别提高了55.7%、24.9%、24.5%、36.5%、120%，对应反硝化还原酶Nap、Nar、Nir、Nor、Nos表达量提高了85.0%、147%、16.5%、47.1%、95.9%。对比体系中“游离细菌”和“Fe3O4粘附细菌”，发现二者的反硝化功能基因以及反硝化相关酶没有显著差别；而Fe3O4粘附细菌电子传递相关蛋白表达量有所提高，说明了Fe3O4通过与细菌直接接触促进其生长代谢，导致体系中细菌总量的增加，从而提高反硝化速率。该结果可为反硝化强化技术的开发提供理论支撑。

Abstract:

Biological denitrification is the most widely used technology for nitrate removal in wastewater treatment. Conventional denitrification requires long hydraulic retention time, and the nitrate removal efficiency in winter is low due to the low temperature. Therefore, it is expected to develop new approaches to enhance the denitrification process. In this paper, the effect of adding different concentrations of Fe3O4 nanoparticles on the denitrification catalyzed by Pseudomonas stutzeri was investigated. The maximum specific degradation rate of nitrate nitrogen improved from 18.0 h–1 to 23.7 h–1 when the concentration of Fe3O4 increased from 0 mg/L to 4 000 mg/L. Total proteins and intracellular iron content also increased along with increasing the concentration of Fe3O4. RT-qPCR and label-free proteomics analyses showed that the relative expression level of denitrifying genes napA, narJ, nirB, norR, nosZ of P. stutzeri increased by 55.7%, 24.9%, 24.5%, 36.5%, 120% upon addition of Fe3O4, and that of denitrifying reductase Nap, Nar, Nir, Nor, Nos increased by 85.0%, 147%, 16.5%, 47.1%, 95.9%, respectively. No significant difference was observed on the relative expression level of denitrifying genes and denitrifying reductases between the bacteria suspended and the bacteria adhered to Fe3O4. Interestingly, the relative expression level of electron transfer proteins of bacteria adhered to Fe3O4 was higher than that of the bacteria suspended. The results indicated that Fe3O4 promoted cell growth and metabolism through direct contact with bacteria, thereby improving the denitrification. These findings may provide theoretical support for the development of enhanced denitrification.