Study On Degradation Property Of Sulfonylurea Herbicides By Composite Bacteria

Sulfonylurea herbicides are widely used in the world.The most widely used herbicides in our country are metesulfuron-methyl,benzenesulfuron-methyl,chlorosulfuron-methyl and so on.It is characterized by its low toxicity,high efficiency,high activity,strong selectivity,dosage of a few grams to dozens of grams per hectare,wide herbicide spectrum,most crops can match its suitable herbicide.With the long-term application of herbicides,the soil contains a large number of herbicides,which seriously damage the ecological environment.Therefore,it is of great significance to study the biodegradation of sulfonylurea herbicides for the degradation of human-made pollutants by microorganisms in the future,and to solve the problem of environmental pollution.In the past,some scholars used composite bacteria to degrade cellulose and other chemical substances,and the effect was better than that of single bacteria,but there were few studies on the degradation of sulfonylurea herbicides by composite bacteria.In this paper,the degradation effect of sulfonylurea herbicides by synergetic action between strains was studied,and a new method and a new way of thinking were provided for the degradation of sulfonylurea herbicides.In this experiment,compound bacteria were used to degrade sulfonylurea herbicides.The main contents were as follows: to determine the composition and structure of compound bacteria by high throughput sequencing,to explore the extraction methods of herbicides and the determination methods of high performance liquid chromatography(HPLC).The degradation of 12 sulfonylurea herbicides by compound bacteria was investigated.Taking the four herbicides with good degradation effect as the research object,the half-life of herbicide degradation by compound bacteria and the influence of environmental factors on the degradation rate were studied,so as to determine the optimum degradation conditions of herbicide by composite bacteria.To explore the application of compound bacteria in field soil.The experimental conclusions are as follows:(1)Using high-throughput sequencing technology,the components of composite strains mainly include Pseudoxanthomonas sp.,Variovorax sp..(2)The extraction of herbicides was carried out by liquid-liquid extraction and the chromatographic conditions were as follows: column temperature: room temperature,detection wavelength: 241 nm,mobile phase: acetonitrile: 1% acetic acid solution = 80:20,flow rate: 1.0 mL/min.(3)All of the herbicides involved in the experiment could be degradedby compound bacteria,but the degradation effects were different.Among them,metosulfuron-methyl,bensulfuron-methyl,formamide-methyl and nicosulfuron-methyl have good degradation effects and can reach more than 85.0%.(4)Compared with the control group,the degradation half-life of the experimental group was significantly shortened.Through the single variable experiment,the optimum conditions of herbicide degradation were obtained:temperature was 20 ℃,pH was 7,initial concentration of herbicide was 50 mg/L,temperature was 20 ℃ and culture cycle was not less than 20 days.(5)In soil medium,the degradation rate of herbicide by compound bacteria reached 50.0%—75.8%,which indicated that the composite bacteria system had certain application in soil environment.