Biotransformation of sulfamethoxazole by a novel strain, Nitratireductor sp. GZWM139: Characterized performance, metabolic mechanism and application potential

A novel strain, Nitratireductor sp. GZWM139 capable of efficient removal of SMX was isolated from mariculture sewage, and Nitratireductor was reported to conduct the removal of antibiotics for the first time. Strain GZWM139 exhibited desirable adaptations to environmental factors with SMX removal efficiencies more than 90 % at temperatures of 28-38 degrees C, pH values of 4.5-8.5, salinities of 20-30 parts per thousand, SMX levels of 1-5 mg/L and shaking speeds of 20-260 rpm. SMX removal was a cooperated process implemented by intracellular enzymes and extracellular enzymes, and was achieved through four proposed biotransformation pathways with the occurrences of demethylation, hydroxylation, nitration, formylation, oxidation, bond cleavage and ring opening. Strain GZWM139 responded to the SMX removal process by altering properties of cell membrane and motivating activities of xenobiotic-metabolizing enzymes and antioxidant system. Genomic analysis proved the existence of functional genes relevant to the SMX removal in strain GZWM139 and provided echoing genetic insights for revealing the SMX removal mechanism. Strain GZWM139 performed efficient detoxification of SMX and accomplished simultaneous removal of SMX and nitrogen in both mariculture sewage and domestic sewage. The findings are significant to the effective elimination of SMX pollution and comprehensive cognitions on metabolic mechanisms of SMX removal.