【摘要】 [目的]分离取代脲类除草剂的高效降解菌,为农药污染土壤的生物修复提供理论依据和物质基础。[方法]从农药厂废水处理池的活性污泥中分离筛选到1株取代脲类除草剂的高效降解菌株,结合形态、生理生化特征和16S rRNA基因序列对其进行鉴定,并研究其降解特性和降解途径。[结果]经鉴定,菌株Pu21为鞘氨醇杆菌(Sphingobium sp.),该菌能同时降解N,N-二甲基取代脲类除草剂异丙隆和N-甲氧基-N-甲基取代脲类除草剂利谷隆。外界温度在25~35℃时对异丙隆和利谷隆降解影响较小,降解2种除草剂的最适温度均为35℃。在初始p H值为6.0~8.0时皆能快速降解异丙隆和利谷隆,最适p H值均为7.0。外加葡萄糖或麦芽糖时,对异丙隆的降解没有影响,但能提高利谷隆的降解,加入蛋白胨或酵母粉后2种除草剂的降解效率都显著提高。降解谱试验表明,菌株Pu21还可以降解敌草隆、伏草隆、绿麦隆、甲氧隆、灭草隆、非草隆和绿谷隆。依据HPLC和MS/MS结果,推测Pu21降解异丙隆途径为:异丙隆脲基侧链N-上脱甲基生成1-(4-异丙基苯基)-3-甲基脲(MDIPU),接着脱甲基生成1-对异丙基苯基脲(DDIPU),断开脲桥形成对异丙基苯胺(4IA)。利谷隆降解途径为:利谷隆脲桥直接断裂生成3.4-二氯苯胺(3,4-DCA)。[结论]菌株Pu21具有优良的降解能力,且降解底物谱广,在取代脲污染土壤的生物修复或生产废水生物强化处理中应用前景广阔。更多还原

【Abstract】 [Objectives]The aim of this study is to isolate high efficient phenylurea herbicides-degrading bacteria,and provide theoretical foundation and material basis for bioremediation of the pesticide-contaminating soil. [Methods]A bacterial strain designated as strain Pu21,capable of degrading phenylurea-herbicides efficiently,was isolated from activated sludge collected from the wastewater treatment system of a pesticide factory,and then identified according to its phenotype,physiological and biochemical characteristics and the similarity analysis of its 16 S rRNA gene sequence. After that,the degradation characteristics and pathway of isoproturon and linuron by Pu21 were studied. [Results]The bacterium Pu21,identified as Sphingobium sp.,could degrade both isoproturon and linuron,which belong to N,N-dimethyl-substituted phenylurea herbicide and N-methoxy-N-methyl-substituted phenylurea herbicide,respectively. This strain could degrade isoproturon and linuron efficiently in the temperature range of 25-35 ℃ and p H value range of 6. 0-8. 0. The optimum temperature and p H value for degradation were 35 ℃ and 7.0,respectively. The addition of glucose or maltose considerably enhanced the degradation rate of linuron rather than isoproturon. However,the degradation rates of these two herbicides were increased significantly while adding peptone or yeast extract as co-substrate. Strain Pu21 could also degrade other phenylurea herbicides such as diuron,fluometuron,ide,chlorotoluron,metoxuron,monuron,fenuron and monolinuron. Based on the data of HPLC and MS/MS results,we proposed isoproturon degradation pathway in strain Pu21. In which,isoproturon was degraded by mono-N-demethylation to yield N-( 4-isopropylphenyl)-N-methylurea( MDIPU),then MDIPU was transformed to 1-( 4-isopropylphenyl) urea( DDIPU) via further N-demethylation,followed by the cleavage of the urea side chain to generate 4-isopropylaniline( 4IA). Using the same methods,we also proposed linuron degradation pathway in strain Pu21. That is,the amide hydrolysis of linuron resulted in the generation of intermediate metabolite 3,4-dichloroaniline( 3,4-DCA). [Conclusions]Strain Pu21 has excellent degradation ability,broad substrate spectrum and great potential for the bioremediation of pesticideΣ contaminating soils and wastewater treatment using bioaugmentation technique.更多还原