Detoxification and degradation of sulfamethoxazole by soybean peroxidase and UV + H₂O₂ remediation approaches

Development of efficient methods for the degradation of emerging pollutants such as pharmaceuticals and pesticides are being recognized as a research priority as more and more of these organic pollutants are being detected in our water bodies. In this work, the degradation of the emerging pollutant sulfamethoxazole (SMX) was carried out using a soybean peroxidase (SBP) enzyme system and an advanced oxidation process (UV + H₂O₂). The optimized conditions for sulfamethoxazole degradation by the peroxidase enzyme showed an absolute requirement for a redox mediator (1-hydroxybenzotriazole) and low pH. The other conditions for an efficient degradation were as follows: [H₂O₂] = 56 μM, [SBP] = 78 nM and [SMX] = 5 ppm. The degradation of the pollutant was followed using UV–Vis spectrophotometry and liquid chromatography–mass spectroscopy (LC–MS). The formed products were identified using liquid chromatography–tandem mass spectrometry. The two remediation methods, an enzymatic approach using SBP + H₂O₂, and the photolytic technique using UV + H₂O₂, generated diverse sets of intermediates, suggesting that different degradation routes were at work in the two systems. Phytotoxicity studies carried out using Lactuca sativa (lettuce) showed different levels of detoxification of the SMX pollutant after the two different remediation treatments.