Screening,Identification And Immobilized Study Of Glufosinate Degrading Bacteria

Glufosinate-ammonium is widely cited for its high efficiency and low toxicity,but its potential harm is easily overlooked.Glufosinate-ammonium has strong water solubility and long-lasting effect,and it is easy to migrate when applying glufosinate-ammonium pesticides in the field,thus polluting surface water and groundwater,and eventually causing chronic toxicity to human body.In this study,the glufosinate-ammonium degrading bacteria ST-3,which was screened by experiments,was used to prepare immobilized beads with sodium alginate and polyvinyl alcohol as carriers.The mechanical properties of the balls were investigated,and finally,the degradation effects of fixed and free ST-3 on glufosinate-ammonium-contaminated soil and water were analyzed by indoor simulation.The experiment provides a certain scientific basis for the practical application of immobilized degrading bacteria.The specific research contents are as follows:1.A total of 6 strains were screened out in the test,and 2 strains were finally obtained after domestication and re-screening.After morphological observation,physiological and biochemical identification and 16 Sr RNA identification,it was determined that TR-2 was Enterobacter horma,ST-3 was Lactobacillus plantarum,Since Enterobacter horma is an enteric pathogen,the follow-up experiments were carried out with Lactobacillus plantarum.2.The optimal growth conditions of strain ST-3 were determined by single factor test:culture temperature 35℃,p H 7.0,inoculum amount 3%,and the growth curve of ST-3 was drawn.The results showed that ST-3 was in 0-6 h is the growth retardation period,8-24 h is the logarithmic growth period,24-30 h is the stable growth period,and after 30 h,it enters the declining period.3.The research on the degradation characteristics of strain ST-3 showed that there was no obvious response to the degradation of glufosinate-ammonium during 0-8 h,the degradation efficiency of glufosinate-ammonium was significantly improved at 16-48 h,and the degradation rate of glufosinate-ammonium after 48 h Slowly,the highest degradation rate of glufosinate-ammonium was 56.21% at 48 h.4.The test is based on the entrapment rate and the degradation rate of glufosinate-ammonium.The optimal immobilization material was selected from the sugar(cross-linking embedding method),and sodium alginate + polyvinyl alcohol with an embedding rate of 77% and a degradation rate of 57% was finally determined as the final material.The material ratio optimized by response surface methodology is: sodium alginate 1.48%,polyvinyl alcohol 9.79%,calcium chloride 1.98%,the immobilized spheres prepared under this condition are uniform in size,and have good mechanical properties and mass transfer performance.The surface of the pellets observed by scanning electron microscopy is uneven and loose and porous,which can provide a large number of effective contact and attachment surface areas for microorganisms,which is conducive to the absorption of nutrients and the transport of metabolic wastes.5.The degradation rates of glufosinate-ammonium in immobilized and free states of ST-3in artificial simulated water were 61.78% and 50.26%,and the degradation rate increased by11.52%;The degradation rates of ammonium phosphine were 50.45% and 41.90%,and the degradation rate was increased by 8.55%.After 6 repeated degradation tests of the immobilized pellets,the degradation rates were all above 30%.