Efficient Sulfamethoxazole Removal by an Isolated Strain Microbacterium esteraromaticum S13.

This study screened and identified a sulfamethoxazole (SMX)-degrading strain of Microbacterium esteraromaticum S13. Degradation characteristics and pathways of S13 strain were investigated, and an immobilization method was applied to enhance SMX removal. The results showed that the strain can tolerate high SMX concentrations up to 150 mg/L and achieved the best removal efficiency at 35 °C, pH 8.0, with an initial SMX concentration of 100 mg/L and the addition of 5 g/L glucose, achieving a removal efficiency of 50.31% within 72 h. The strain also showed good removal potential for other sulfonamide antibiotics (SAs), including sulfadiazine, sulfamethazine, and sulfadimidine, with removal efficiencies all exceeding 61%, and also demonstrated a removal efficiency of 53% for amoxicillin. Three potential biotransformation pathways were proposed based on four transformation products identified by LC-MS analysis and relevant reported studies. Finally, S13 cells immobilized with polyvinyl alcohol and sodium alginate resulted in a significantly improved degradation rate of SMX. Nearly 100% removal of 100 mg/L SMX was achieved within 24 h, and S13-immobilized gel beads maintained a degradation rate of over 85% even after four consecutive rounds of degradation. These results strongly demonstrated the potential of the S13 strain to degrade antibiotics and provided a solid foundation for advancing the removal of SAs in the environment.