Alginate-Driven Co-metabolic Degradation Mechanism of Sulfamethoxazole by Marine Consortia

Pharmaceuticals and personal care products (PPCPs), known for their severe ecological risks, are frequently detected in coastal waters worldwide. However, the environmental fate in marine systems remains poorly understood. This study investigated the co-metabolic degradation mechanism of a typical PPCP, sulfamethoxazole (SMX), by a marine consortium SAB using alginate—a natural organic matter—as a co-substrate, aiming to elucidate the biodegradation process of PPCPs in actual marine environments. An integrated approach, including metagenomic sequencing (with binning), RT-qPCR, molecular docking, metabolic modeling, and metabolomics, was employed. Results demonstrated that the SAB consortium efficiently degraded SMX at concentrations from 50   μg/L to 10   mg/L, achieving over 96% removal within 24   h. SMX degradation was achieved through metabolic cross-feeding of alginate by key species within the SAB consortium. Specifically, alginate is initially converted by Vibrio into the central metabolite 2-keto-3-deoxy-D-gluconate (KDG). KDG is subsequently metabolized by Tritonibacter , Halopseudomonas , and Vibrio , generating key metabolites such as acetyl-CoA, serine, cysteine, and guanine. These metabolites support microbial growth and induce production of SMX-degrading enzymes, such as threonine dehydratase, cysteine S-conjugate β-lyase, and guanine deaminase, leading to SMX cleavage and mineralization. Additionally, acetyl-CoA provides acetyl groups for arylamine N-acetyltransferase-mediated SMX acetylation. These processes collectively drive the co-metabolic degradation of SMX. Overall, this study provides critical insights into PPCPs' fate in marine environments.