Efficient degradation of tylosin by <i>Kurthia gibsonii</i> TYL-A1: performance, pathway, and genomics study

Tylosin is a commonly used macrolide antibiotic, which is commonly utilized in livestock; its release through animal excrement can have detrimental environmental effects. Biodegradation of tylosin (TYL) is an effective bioremediation method. In this study, we identified a novel and efficient TYL-degrading bacterial strain, <i>Kurthia gibsonii</i> TYL-A1, capable of degrading 75 mg/L of TYL within 5 days at 30°C, pH 7, with 3% inoculum and yeast extract as the nitrogen source. The bacterium degraded 99% of 75 mg/L TYL in 5 days. Both intracellular and extracellular enzymes collaborated to degrade TYL. Metabolites were analyzed by liquid chromatography-mass spectrometry (LC-MS), revealing that strain TYL-A1 could remove mycophenolic sugar, cleave the ester bond, and further degrade TYL into smaller molecules. The toxicity of the degradation products was lower than that of the parent compound and its natural degradation products. Whole-genome sequencing results indicated that genes encoding glycoside hydrolases and glycosyltransferases, along with metabolism-related genes, were involved in TYL degradation. This study elucidated the degradation mechanism of TYL and highlighted the potential of strain TYL-A1 to remove TYL from the environment.IMPORTANCETylosin (TYL) contamination has become a hot issue, and microbial removal systems have been widely considered as an economical and environmentally friendly alternative. Our study proposed a new TYL degradation pathway through the biological metabolic pathway of LC-MS metabolite analysis. Whole-genome sequencing further provided the genetic mechanism involved in the degradation process and explained the degradation effect of strain TYL-A1 on TYL. The application of TYL-A1 to actual wastewater highlights the practical relevance of TYL pollution in the environment. This application highlights the importance of microbial germplasm resources in the bioremediation of TYL-contaminated ecosystems. All in all, our study provides a theoretical basis for reducing the pollution of antibiotics in the environment and promoting the sustainable development of the ecological environment.