Degradation of sulfamethoxazole by a Pseudomonas consortium: co-substrate promotion mechanisms, accelerated immobilization and microbial community dynamics in wastewater application

Sulfamethoxazole (SMX)-degrading bacteria have been isolated previously but were rarely applied into realistic wastewater due to poor colonization and instability. In this study, an efficient SMX-degrading bacteria consortium, dominated by Pseudomonas , was enriched from activated sludge and systematically evaluated for accelerated immobilization and application in the treatment of realistic municipal wastewater. The results showed that co-substrate addition markedly enhanced consortium growth and SMX degradation. Co-substrate type further governed immobilization: glucose accelerated biofilm formation on raw carriers, whereas sucrose favored planktonic growth and required chitosan-modified electrophilic carriers for effective immobilization. Co-substrate-assisted immobilization shortened the period from over 40 d to <10 d. Moreover, the immobilized consortia exhibited a remarkably SMX degradation efficiency with ∼3 h half-life, which was strongly correlated with total attached consortium DNA ( r  = 0.988). The immobilized consortia achieved stable SMX removal (>99.8%) over 30 d of cyclic operation in realistic municipal influent and effluent wastewater, respectively, proving its applicability as bio-augmentation in secondary and polishing treatment for SMX. Microbial community analysis revealed persistent Pseudomonas dominance with adaptive diversification driven by co-substrate regime, carrier type, and wastewater conditions. Overall, this study highlights rational co-substrate selection and carrier design as key determinants for efficient immobilization and long-term performance of slow-growing antibiotic-degrading consortia, providing a scalable strategy for sulfonamide antibiotics removal in wastewater treatment systems.