Study on Strains Degrading Veterinary Antibiotics in Activated Sludge

Abstract

Currently, veterinary antibiotics are widely used in China's aquaculture industry and play an important role in animal husbandry. However, due to insufficient supervision, the abuse of veterinary antibiotics is relatively severe. Particularly concerning the production of veterinary antibiotics and the treatment of animal husbandry wastewater, clear discharge limits have not yet been established, making the treatment of antibiotic wastewater extremely urgent. An SPE–HPLC protocol was developed for the first simultaneous quantification of tylosin (TYL) and tylvalosin (TAT) in wastewater matrices. The calibration curves were linear over 0.5–1000 mg L⁻¹ (R² ≥ 0.9995), delivering LODs of 0.20 mg L⁻¹(TYL) and 0.15 mg L⁻¹(TAT) and corresponding LOQs of 0.50 mg L⁻¹and 0.42 mg L⁻¹. Spiked real-wastewater recoveries spanned 74.3–97.3 % with RSDs below 8.8 %, confirming reliable accuracy and precision. Subsequently, six strains capable of degrading TYL and TAT were isolated from activated sludge. Among them, Providencia vermicolastrain CT1 showed the best degradation effect on TYL and TAT. At 30 °C, pH 6.0 and 50 mL inoculum, the isolate removed 90.7 % of 200 mg L⁻¹ TYL and 94.8 % of 300 mg L⁻¹ TAT within 48 h. GC-MS analysis was employed to characterize TAT metabolites, enabling reconstruction of the microbial catabolic pathway. Strain CT1 showed significant treatment effects on actual wastewater containing TYL and TAT, achieving degradation rates of 95.3% for TYL and 93.7% for TAT, along with degradation rates of 97.8% for NH₃-N, 92.9% for COD, and 80.7% for BOD₅.