Degradation and transformation of tylvalosin by newly selected Providencia vermicola strain CT1: removal efficiency, pathways, mechanisms, and actual applications

Tylvalosin (TAT) is a widely used veterinary antibiotic whose residual contaminants promote antibiotic resistance and pose potential risks to human health and ecosystems. This study successfully isolated and identified a TAT-degrading bacterial strain, Providencia vermicola strain CT1, through 16S rRNA analysis and biochemical tests. Under optimized conditions (30 °C, pH = 6, initial TAT concentration of 300 mg/L, and bacterial culture volume of 50 mL), strain CT1 achieved a TAT degradation percentage of 97.1%. The degradation process followed a first-order kinetic model and was primarily driven by extracellular metabolites. GC-MS analysis identified that strain CT1 degrades TAT to produce small molecules such as 3-methylbutanoic acid, ethyl acetate, and 3-iminopentan-2-one. Strain CT1 effectively degraded TAT in actual wastewater samples, achieving 95% degradation within 60 h, and significantly reduced the COD, BOD₅, and NH₄⁺-N concentrations. These findings provide theoretical guidelines for removing TAT and other macrolide antibiotic contaminants from the environment.