Expression and application of α/β hydrolase from Kurthia gibsonii TYL-A1

Tylosin (TYL), a widely used macrolide antibiotic in livestock and poultry production, has attracted considerable attention owing to its strong adsorption capacity, persistence, and ecological risks in aquatic and soil environments. Because of their high efficiency and substrate specificity, microbial degradation enzymes are among the most promising agents for removing TYL from the environment. In this study, α/β hydrolase (Rcmd-2829) was expressed and purified from Kurthia gibsonii TYL-A1. The results showed that the optimum reaction conditions for Rcmd-2829 were pH 9.0 and 30°C. Molecular docking analyses, molecular dynamics simulations, and site-directed mutagenesis confirmed the key role of the Ser-102 residue in the catalytic degradation of TYL by Rcmd-2829. Rcmd-2829 retained its high catalytic activity in aquaculture wastewater, removing 83 % of 150 mg/L of TYL within 5 d. This study is the first to elucidate the Ser-102-dependent molecular mechanism underlying TYL degradation by the α/β hydrolase Rcmd-2829, providing a foundation for the development of efficient enzymatic-remediation technologies.