Optimization of degradation conditions and elucidation of novel biodegradation pathways for sulfamonomethoxine by a novel Bacillus strain.

As a commonly used sulfonamide antibiotic, the efficient reduction of sulfamonomethoxine (SMM) residue in the environment is a critical issue that urgently needs to be addressed. However, there is limited understanding of the microbial conditions needed for efficient SMM degradation and its mechanisms. Therefore, this study screened a new strain, Bacillus sp. DLY-11, from swine manure compost with significant SMM degradation capability, and utilized response surface methodology (RSM) based on Box-Behnken design to optimize the degradation conditions. The results showed that under conditions of a 5% inoculation volume, a temperature of 59.1°C, a pH value of 7.10, and 0.45 g/L MgSO₄, strain DLY-11 could degrade 98.8% of 20 mg/L SMM within 48 h. Product analysis identified six potential transformation products and proposed two potential biodegradation pathways of SMM, including C-N bond cleavage, hydroxylation, and SO₂ release. Particularly, we discovered a novel degradation pathway that has not been reported before. This study not only introduced a new strain for efficient SMM degradation but also optimized conditions and revealed new degradation pathways. These findings addressed gaps in bacterial SMM degradation pathways, offering theoretical and technical support for bioremediating antibiotic pollutants in animal husbandry.

Importance: The discovery of a new Bacillus sp., strain DLY-11, from aerobically composted swine manure offers significant environmental benefits by efficiently degrading 98.8% of 20 mg/L sulfamonomethoxine (SMM) within 48 hours under optimal conditions (5% inoculation volume, 59.1°C, pH 7.10, 0.45 g/L MgSO4). This strain introduces a new tool for reducing SMM antibiotic pollution and reveals a novel degradation pathway, enhancing our understanding of SMM biodegradation mechanisms and supporting targeted bioremediation strategies.