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 (Ki) and semi-saturation (Ks) 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 co-metabolic culture for microbial remedied of norfloxacin-contaminated environments.