Combination of enzymatic degradation by chloroperoxidase with activated sludge treatment to remove sulfamethoxazole: performance, and eco-toxicity assessment

Abstract

BACKGROUND Sulfamethoxazole is found in surface and ground waters because it is usually not metabolized and simply passes through the human body after ingestion. This drug is difficult to degrade by conventional treatments and may cause environmental concerns. RESULTS A rapid and efficient enzymatic degradation of sulfamethoxazole by a heme peroxidase, chloroperoxidase (CPO), was investigated in this work. The degradation efficiency of sulfamethoxazole reached 98.64% within 20 min at room temperature, atmospheric pressure and environment‐friendly reaction conditions with an enzyme concentration of approximately 10−9 mol L−1. High performance liquid chromatography–mass spectrometry analysis was employed to identify the intermediates and final products. Moreover, chemical oxygen demand (COD) measurements showed that pre‐treatment by CPO‐H2O2 oxidative degradation followed by existing bioremediation technologies can effectively improve the efficiency and thoroughness of decontaminating this drug from wastewater. The degradation efficiency was enhanced from 76.5% to 84.47%, and the COD removal increased from 29.72% to 51.32%. The eco‐toxicity test using a green algae, Chlorella pyrenoidos, showed that the degraded products had lower toxicity than the parent drug. CONCLUSION CPO catalyzed oxidative degradation is a promising alternative for treatment of wastewater containing sulfonamide drugs. This enzymatic method is also suitable for treatment of other sulfonamide antibiotics. © 2016 Society of Chemical Industry

Chloroperoxidase-Mediated Halogenation of Selected Pharmaceutical Micropollutants

“…No reaction was detected under peroxidase activity conditions (pH 5.0-6.0, and/or in the absence of chlorine ions) for any of the PhCs tested. Some of the reaction products have been previously reported [41][42][43]. However, two PhCs showed unique behavior under our tested conditions.…”

“…For example, the kcat/Km values for 2,3,5,6-tetrachlorophenol, pentachlorophenol, 2,3,5,6-tetrachloroaniline, and parathion are 2028, 470, 133, and 33 s −1 •mM −1 , respectively [27,39]. High conversions for the PhCs estradiol, sulfamethoxazole, diclofenac, and naproxen by CPO oxidation have also been previously reported [41,42]; however, no kinetic data were available for these compounds. Such data are useful to design …”

“…The biodegradability indexes of the oxidized products were higher than those of the corresponding unchlorinated substances, except in the case of estradiol (Figure 4). This last result may be explained by the fact that chlorinated products of estradiol are more toxic towards the inoculum than the original substance (Table S3); this suggests that the enzymatic products may have a different type of toxicity, not related to endocrine activity but another form of toxicity that inhibits the respiration of the microorganisms [41,42].…”

“…For instance, halogenated derivatives of β-estradiol have been reported to retain little estrogenic activity [43,47]. Additionally, in a previous work, the chlorination of sulfamethoxazole, diclofenac, and naproxen by CPO produced halogenated products with greater biodegradability and lower toxicity than the original drugs [41,42]. Because the authors of that study used an adapted inoculum from a biological reactor of a secondary treatment stage, an investigation of the biodegradability of the reaction products in natural water bodies, where non-adapted microorganisms could encounter these compounds, is still required.…”

“…Finally, the halogenated products of sulfamethoxazole were different from those previously reported. According to Zhang et al, sulfamethoxazole first undergoes halogenation, followed by ring opening [42]. In this work, only fragments were observed after the reaction: one product with a molecular formula of C 10 H 11 ClN 3 O 3 S (m/z 288.0254) and another one with a formula of C 4 H 5 NO 3 (m/z 145.00), probably as a result of more extensive oxidation due to the concentration of activating salts.…”