Study On Isolation And Characterization Of A Trifluralin-degrading Strain D8 And Its Degrading Characteristics

Trifluralin is a widely used dinitroaniline selective preemergic herbicide,mainly used for beets,cotton,tomatoes and other 40 kinds of crops and orchards,forestry nursery and other control of annual grass weeds and some dicotyledonous weeds.Due to broad spectrum,the nature and effect of stability,long duration and other characteristics,to be widely promoted and used in the world,but it has the characteristics of poor leaching,can be adsorbed by soil particles and accumulated in the topsoil,it.s difficult to be washed away by rain or leaching to the bottom of the soil layer and residual in the soil,a small amount of trifluralin remained in the soil for up to two years and had an effect on crop emergence and growth,there is a certain harm to ecological environment and post – crop.In this paper,the microbial degradation technology was studied for the residual pollution of trifluralin,the method of dilution and culture was used to screen the highly effective degrading bacteria,the morphological characteristics,physiological and biochemical characteristics and 16 Sr DNA sequence analysis were used to determine the phylogenetic status of a strain with the best degradation ability;The optimum degradation conditions were studied by single factor experiment;The chemical constituents of sample were analyzed by HPLC-MS,and the degradation pathways of the degradation strains were studied.The main findings are as follows:(1)A direct dilution coating method was used to isolate one strain of D8,which could degrade trifluralin,from the soil of cotton field for more than 15 years,the strain D8 was identified as Bacillus cereus by its morphological characteristics,physiological and biochemical characteristics and 16 S rDNA gene sequence analysis.(2)The optimum substrate concentration of the strain D8 was 50 mg / L,the inoculation amount was 4%,the addition of nitrogen source was 0.1% yeast extract,temperature 37 ℃,pH Was 5.0,and the degradation rate of the strain was more than 59.89% when cultured for 3 days under the above conditions.(3)Using the Agilent C-18 reverse column,column temperature is 30 ℃,mobile phase A phase is pure water,B phase is methanol,flow rate 1 m L / min for full-wavelength scanning UV detection,under the same conditions,the samples were chemically analyzed and identified by HPLC-MS,the possible degradation of the degradation of trifluralin by Bacillus cereus was dealkylation,nitro reduction and cyclization the main degradation products were2-ethyl-7-nitro-1-propyl-5-trifluoro Methylbenzimidazole,3-nitro-5-trifluoromethylaniline and 2-ethyl-7-nitro-5-trifluoromethylbenzimidazole.