| With the unreasonable use of herbicides,herbicide residue pollution has become an urgent problem to be solved.Compared with physical remediation and chemical remediation,microbial remediation has become a major trend in herbicide remediation in recent years due to its advantages of low cost,better effect and less environmental disturbance.As herbicides commonly used in corn fields in cold regions of north China,the residues of nicosulfuron and atrazine will pollute the ecological environment,affect the yield and quality of later crops,change the microbial biomass,and harm human and animal health.Screening efficient biodegradable strains of nicosulfuron and atrazine,and exploring the optimal fermentation and degradation conditions of biodegradable strains can provide new strains for herbicide biodegradable microbial resource bank,improve the soil environment in black earth in a cold region,improve the yield and food security of post-stubble crops in corn fields,and promote the high-quality development of Chinese agriculture.It can provides the scientific basis for the remediation of herbicide residue pollution in black soil of cold region in China.In this study,nicosulfuron-degrading strain N23 and atrazine degrading strain A16 were isolated through microbial screening and domestication,and their growth conditions and degradation characteristics were studied.The main results are as follows.(1)N23 was screened by microbial isolation and acclimation,and was identified as Acinetobacter radioresistens.After 16 d incubation in MSM+ nicosulfuron medium,the degradation rate of strain N23 to nicosulfuron at 200 mg/L concentration was 67.96%.The optimal growth conditions and degradation conditions of strain N23 were studied by single factor experiment.The results showed that the optimal growth conditions of strain N23 in LB medium were culture temperature 30℃,200 r/min,pH6.0 and inoculation dosage is 2%.The optimal environmental conditions for degradation of strain N23 in MSM+ nicosulfuron medium were culture temperature 30℃,200 r/min,pH6.0,inoculation dosage is 7% and initial substrate concentration of 200 mg/L.(2)Atrazine degrading strain A16 was screened by microbial isolation and acclimation,and identified as Pseudarthrobacter niigatensis.The degradation rate of atrazine to 400 mg/L was100% after being cultured in MSM+ atrazine medium for 3 days.The optimal growth and degradation conditions of strain N23 were studied by single factor experiment.The results showed that the optimal growth conditions of strain A16 in LB medium were 30℃,200 r/min,pH6.0 and inoculation dosage is 2% amount.The optimal conditions for degradation of strain A16 in MSM+ atrazine medium were culture temperature 30℃,160 r/min,initial pH7.0,inoculation dosage is 5% and initial substrate concentration 400 mg/L.(3)The degradation effect of degraded strains in soil was simulated under laboratory conditions.The results showed that the degradation rate of strains N23 and A16 in unsterilized soil was higher than that in sterilized soil,and the ability to degrade herbicides decreased with the increase of the initial concentration of herbicides.In the unsterilized soil samples with 50mg/kg nicosulfuron and atrazine,the degradation rates of the two herbicides were 28.43% and79.53%,respectively,for the composite strains N23 and A16. |
