Sulfachloropyridazine (SCP) effects on anaerobic microorganisms and its degradation pathways

Sulfachloropyridazine (SCP) is frequently detected in animal excreta, as SCP commonly used in livestock and poultry for disease prevention. Anaerobic digestion (AD) has attracted much attention due to its ability to degrade antibiotics in animal excreta and convert animal excreta into renewable energy (biogas). But the degradation pathways of SCP in AD microorganism growth and SCP effect on the growth of AD microorganism are still unclear. In this study, the impact of SCP at 100 mg/L on the growth of representative AD microorganisms and the degradation pathways of SCP during single microorganism growth process were investigated using a pure culture method. Results showed that SCP has no effect on the growth of Clostridium tyrobutyricum and Methanosarcina barkeri, a positive effect on Peptoniphilus stercorisuis, but an inhibitory effect on Terrisporobacter glycolicus, Bacteroides caccae, and Proteiniphilum saccharofermentans, based on changes of cell growth (OD600), cumulative gas production, and gas components of strains. Meanwhile, SCP was degraded in varying degrees during the whole growth cycles of P. saccharofermentans, T. glycolicus, C. tyrobutyricum, B. caccae, P. stercorisuis, and M. barkeri, with degradation rates of 80.9%, 43.5%, 56.7%, 70.8%, 51.0%, and 21.4%, respectively. The SCP degradation pathway is different for these different strains, but the common degradation pathways were hydroxylation, C-N bond cleavage, release SO2, and nitration. These results revealed that anaerobic microorganisms have the high capability of degrading antibiotics and revealing degradation pathway is important for improving antibiotic degradation in AD process.