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Antibiotic biodegradation is the microbially mediated transformation and mineralization of antibiotic compounds—such as sulfonamides, tetracyclines, fluoroquinolones, and macrolides—into less toxic or innocuous metabolites, carbon dioxide, water, and inorganic nitrogen or sulfur under aerobic or anaerobic conditions ^[1]. The process is carried out by specialized bacterial strains and mixed microbial communities, including ammonia-oxidizing bacteria and heterotrophic degraders, that express enzymes such as flavin-dependent monooxygenases and reductases which initiate attack on specific molecular substructures—for example, ipso-hydroxylation of the sulfonamide aromatic ring followed by cleavage of the sulfonamide bond to release the aniline fragment and the isoxazole side chain ^[2]. Biodegradation kinetics depend on antibiotic concentration, temperature, pH, nutrient availability, redox conditions, and whether the antibiotic serves as a primary carbon and energy source or is co-metabolized with another substrate; incomplete degradation can produce transformation products that retain antimicrobial activity and contribute to the spread of antibiotic resistance genes in the environment ^[3].