Isolation and characterization of a norfloxacin-degrading bacterial strain Aeromonas hydrophila sp. N215-1

Norfloxacin, a third-generation fluoroquinolone antibiotic, is increasingly used in the treatment of human and animal diseases, and being frequently detected in the environment. Norfloxacin has a broad spectrum of antibacterial activity, so few bacteria can degrade norfloxacin effectively. This is the first report on norfloxacin biodegradation by Aeromonas hydrophila sp. N215-1. Response surface methodology was employed to optimize the bacterial growth and degradation of norfloxacin of strain N215-1 in flask scale. The maximum yield of 0.31 in OD60f0 and 25.0% in degradation efficiency in 24 h were obtained when using RSM optimized medium, which improved strain growth and degradation by 3.88 and 5.68-fold, respectively. The kinetic analysis indicated that strain N215-1 could grow with the maximum specific growth rate, inhibit constant (K-i) and semi-saturation (K-s) constant of 0.2640/h, 23.9909 mg/L and 1.9817 mg/L, respectively. Furthermore, the optimized medium was applied in an 85 L modified AAO reactor with 2% N215-1 bioaugmentation, an increased norfloxacin removal rate from 56.0% to 81.2% was achieved. This study highlights a significant potential of using microbial cometabolic culture for microbial remedied of norfloxacin-contaminated environments.

Automated summary

This study presents the biodegradation of norfloxacin by Aeromonas hydrophila sp. N215-1 and optimization of bacterial growth and degradation using response surface methodology. The results demonstrate that the optimized medium significantly improves the growth and degradation efficiency of the strain. Furthermore, the optimized medium applied in a modified AAO reactor with bioaugmentation achieves a higher norfloxacin removal rate.