过表达亚硝酸盐还原酶的重组大肠杆菌辅助污水短程硝化

【目的】为了体现并突出亚硝酸盐还原酶在污水脱氮以及短程硝化中的重要性,对过表达亚硝酸盐还原酶的大肠杆菌进行了污水脱氮的研究。【方法】通过转化带有亚硝酸盐还原酶基因的重组质粒,将亚硝酸盐还原酶在大肠杆菌中过表达,通过分析重组大肠杆菌的产物研究了该酶的表达及还原亚硝酸盐的情况,通过将该重组菌与已报道的硝化-反硝化细菌或生活污水进行混合培养,研究重组菌用于辅助氨氮去除的短程硝化能力。【结果】重组大肠杆菌能正确表达亚硝酸盐还原酶,OD600=2.0的菌悬液在2 h内还原约1 mmol/L的亚硝酸盐,并产生几乎等量的一氧化氮;重组大肠杆菌与Acinetobacter sp.YF14菌株等比例混合时,12 h能够提高氨氮脱氮效率约(36.0±7.4)%,且在4 h时,最大亚硝酸盐的积累量减少37%;重组大肠杆菌(OD600=1.0)12 h内能够提高污水厂活性污泥的脱氮效率约(31.0±5.7)%,且未检测到亚硝酸盐和硝酸盐的积累;溶氧水平对于亚硝酸盐还原酶重组菌辅助脱氮具有明显的影响,中等溶氧量(6.4?0.7)mg/L]时脱氮效果最好。【结论】过表达亚硝酸盐还原酶的大肠杆菌可以提高污水脱氮的短程硝化能力。

Shortcut nitrification of sludge by recombinant Escherichia coli overexpressing nitrite reductase

Objective] To highlight the significance of nitrite reductase in wastewater denitrification and shortcut nitrification, we studied wastewater denitrification by Escherichia coli expressing nitrite reductase.Methods] Nitrite reductase was overexpressed by transformed a recombinant plasmid with nir gene in E. coli. Expression of nitrite reductase and metabolism of nitrite were studied by detecting the products in the whole cell of recombinant E. coli. To evaluate the function of recombinant E. coli used for shortcut nitrification, we measured the denitrification efficiency of the mixture consisting of the recombinant E. coli and YF14 that was a nitrifying and denitrifying bacterium.Results] The recombinant E. coli could express nitrite reductase, reduced about 1 mmol/L nitrite within 2 hours and produced almost equal amounts of nitric oxide (OD₆₀₀=2.0 bacterial suspension). When the recombinant E. coli and YF14 were mixed in equal proportions, the ammonia nitrogen removal efficiency increased by about (36.0±7.4)% within 12 hours, and the maximum accumulated amount of nitrite decreased by about 37%. Recombinant E. coli (OD₆₀₀=1.0) significantly improved the ammonia nitrogen removal efficiency of activated sludge by about (31.0±5.7)% within 12 hours, and no nitrite and nitrate were detected. Oxygen supply affected ammonia nitrogen removal with optimal DO of (6.4±0.7) mg/L.Conclusion] Recombinant E. coli with nitrite reductase can contribute to the shortcut nitrification capacity of wastewater.