Screening Of Chlortetracycline-Degrading Strains And Study On Biodegradation Mechanism

In recent years,more and more attention has been paid to the retention and accumulation of antibiotics in the environment.Chlortetracycline is widely used in veterinary drug feed,aquaculture,animal husbandry and other industries.It has been found that chlortetracycline can not be completely absorbed by passive objects and discharged into the environment.Impact on the environment and ecology.Three pure strains with high degradation of chlortetracycline were isolated from the sludge of chlortetracycline feed factory,named bm,green and fui,as Acinetobacter sp.,Bacillus sp.and Aspergillus sp.,respectively.Through orthogonal experiment and response surface optimization experiment,the optimum environmental conditions of strain bm were as follows:the initial concentration of chlortetracycline was 134.86 mg/L,the temperature was 34.41?,the amount of inoculation was 5.22 v/v,and the degradation efficiency of chlortetracycline was 93.72%.The optimal environmental conditions of strain green were as follows:the initial concentration of chlortetracycline was 128.14 mg/L,the temperature was 25.40?,the amount of inoculation was 2.84 v/v,and the degradation efficiency of chlortetracycline was 67.59%.The optimal environmental conditions of strain fui were as follows:the initial concentration of chlortetracycline was 80.14 mg/L,the temperature was 30.93?,the amount of inoculation was 3.64 v/v,and the degradation efficiency of chlortetracycline was 95.40%.The whole genome of strain fui was sequenced.The fui genome contains 50.1%Mb,GC and encodes 12825 genes.The total gene length is 22377825 bp,.Through the annotation analysis of GO database,eggNOG database and KEGG database,it is found that the fui genome contains enzyme genes for degradation of chlortetracycline and its intermediates,biodegradation process genes and multiple antibiotic resistance genes.Strain fui produce dehydrogenase,oxidoreductase,hydrolase,reductase and other enzyme gene through detoxification,immune system process,metabolic process and othe biological processes to biodegrade and metabolize chlortetracycline.The degradation intermediates and degradation pathways.chlortetracycline are speculated.Chlortetracycline is degraded through a serie:of pathways such as demethylation,dehydration,decarbonylation,deamidatior and deamidation.In addition,chlortetracycline may quickly decompose the four-ring structure of chlortetracycline into a double-ring structure through the direct cracking of D-ring or B-ring,which may be the unique degradation mode of strain fui,and the final degradation product of chlortetracycline is presumec to be single-ring or long-chain structure.The complete degradation of chlortetracycline is basically achieved,which is of great significance for the degradation of chlortetracycline by a single strain.