Screening and Identification of Enrofloxacin Degrading Strain and Optimization of Its Degradation Conditions

In order to study the biodegradation of enrofloxacin,a strain was screened from the the gut of black soldier fly,which had been used to treat the pig manure containing enrofloxacin for a long time. The intestinal juice of black soldier fly was cultured in the medium containing enrofloxacin. After twice screening,the strain with the strongest ability to degrade enrofloxacin was selected from several strains with the ability to degrade enrofloxacin. The optimal degradation conditions were determined by single factor experiment: Temperature,initial pH,inoculum amount and shaking speed. According to the results of single factor experiment,the optimal degradation conditions were obtained by response surface analysis. Results showed that,17 strains of enrofloxacin degrading bacteria were obtained in the initial screening,and 3 strains of enrofloxacin degrading bacteria were found in the further re-screening. BSFL-1 and BSFL-3 were identified as Enterococcus faecalis and BSFL-2 as Proteus mirabilis. The strain with the highest degradation rate was BSFL-3. By response surface analysis,the optimal degradation conditions were as follows:Temperature 33.6 ℃,initial pH5.8,inoculation amount 4%,shaking speed 155 r/min. Under these conditions,the degradation rate of enrofloxacin was 77.83%±0.53%. The strain with optimized degradation conditions has high degradation rate,which broadens the research field of biological degradation of enrofloxacin,and provides help for the application research of using bacterial degradation rate of enrofloxacin.