Immobilization And Application Of Glyphosate Degrading Bacteria

Glyphosate is a possibly carcinogenic substance that is prevalent in surface and groundwater,causing significant pollution to the environment.Therefore,this study planned to screen glyphosate degrading bacteria,and after embedding and immobilization,the immobilized degrading bacteria was applied to glyphosate wastewater treatment through relevant process optimization,and the following results were obtained:(1)A highly efficient glyphosate degrading bacterium k6 was screened from the soil.After shaking for 24 h in 500 mg/L glyphosate sole carbon and nitrogen source screening medium,the degradation rate of glyphosate was 95.68%.After 16S r DNA gene alignment,the degrading bacterium k6 was preliminarily identified as Shinella zoogloides.(2)After optimization of the entrapment process by considering the microbial entrapment rate,glyphosate degradation rate and physicochemical properties comprehensively through single factor tests and orthogonal tests,the optimal preparation process of microcapsules for immobilization of glyphosate degrading bacteria was determined to be 50 g/L of sodium alginate,3 g/L of activated carbon,40 g/L of calcium chloride and 9×10~9CFU/m L of bacteria,cross-linking time 12 h;After optimization and incubation with shaking for 24 h,the immobilized microcapsules of glyphosate degrading bacteria can reach 97.07%degradation rate of glyphosate.(3)The microcapsules and bacterial solution prepared by immobilization of glyphosate degrading bacteria were added to different cultivation environments,and it was found that microcapsules can degrade glyphosate under wide temperature and p H conditions.Under weak acid,weak base,and UV irradiation conditions,the degradation rate of glyphosate by immobilized microencapsulated bacteria was significantly higher than that of free bacteria.(4)When the microcapsules were applied to river water,after 2 d of treatment,the CK and W groups had glyphosate levels of 107.87 mg/L and 2.87 mg/L,respectively,and aminomethyl phosphate levels of 0 mg/L and 51.69 mg/L,respectively.The incorporation of microcapsules could quickly reduce the glyphosate content in river water and alleviate its environmental pollution.After being treated with glyphosate degrading bacteria microcapsules,the significant inhibitory effect of glyphosate on plant seed growth in river water could be relieved.(5)Further examination of the microbial community changes in river water revealed that the bacterial community diversity and uniformity were higher in the microcapsule group than in the control group,and the dominant bacterial phyla in the microcapsule group and control group were Proteobacteria,Actinobacteria,Cyanobacteria and Bacteroidota.At the genus level,the dominant bacterial genera included Chloroplast and Niveispirilum,hgc I＿clade,Sporichthyaceae.In the detection of fungal community,the dominant fungal phyla included Ascomycota,Basidiomycota,and Chytridiomycota,and the fungal genera were Candida,Fusarium,Linnemannia,and Cladosporium.