School of Energy and Environment, Southeast University, No.2, Sipailou, Nanjing, Jiangsu 210096, China; State Key Laboratory of Environmental Medicine Engineering, Ministry of Education, Southeast University, Nanjing 210096, China.
School of Energy and Environment, Southeast University, No.2, Sipailou, Nanjing, Jiangsu 210096, China; State Key Laboratory of Environmental Medicine Engineering, Ministry of Education, Southeast University, Nanjing 210096, China.
Water Res. 2022 Jul 15;220:118623. doi: 10.1016/j.watres.2022.118623. Epub 2022 May 16.
Co-metabolism and photodegradation are two approaches for remediating trace organic compounds (TOrCs), however, interactions between the two with regards to TOrCs degradation have not been elucidated. In this study, sulfadiazine (SDZ) was chosen as a representative TOrC and Methylocystis bryophila as a typical strain. Under light conditions, about 80.6% of SDZ was removed by M. bryophila, but only 7.6% or 28.9% of SDZ was eliminated by either individual photodegradation or by co-metabolism. The SDZ stimulated more extracellular organic matter (EOM) production by M. bryophila. The enhanced SDZ degradation was attributed to indirect photolysis caused by the excited triplet state of EOM (EOM*) and co-metabolism. The UPLC-QTOF-MS analysis showed that due to co-metabolism, the pyrimidine ring was broken and could further be oxidized into smaller molecules under light conditions, such as formic and acetic acids. The SDZ mineralization ratio increased from 9.9% under the co-metabolic condition alone to 36.5% under co-metabolism coupled with photodegradation. The Ames tests confirmed that the SDZ degradation products by co-metabolism were mutagenic, however, their toxicity was ameliorated by light during co-metabolism. In conclusion, light plays a crucial role in co-metabolic processes of TOrCs.
共代谢和光降解是修复痕量有机化合物 (TOrCs) 的两种方法，但关于 TOrCs 降解的两种方法之间的相互作用尚未阐明。在这项研究中，磺胺嘧啶 (SDZ) 被选为代表性的 TOrC，而聚球藻属 (Methylocystis bryophila) 则作为典型的菌株。在光照条件下，M. bryophila 去除了约 80.6%的 SDZ，但单独的光降解或共代谢分别去除了 7.6%或 28.9%的 SDZ。SDZ 刺激了更多的胞外有机物 (EOM) 由 M. bryophila 产生。增强的 SDZ 降解归因于 EOM*（EOM*）激发三重态引起的间接光解和共代谢。UPLC-QTOF-MS 分析表明，由于共代谢，嘧啶环被打破，并在光照条件下进一步氧化成较小的分子，如甲酸和乙酸。SDZ 的矿化率从单独共代谢条件下的 9.9%增加到共代谢与光降解耦合下的 36.5%。Ames 测试证实，共代谢降解的 SDZ 产物具有致突变性，但在共代谢过程中光的存在减轻了其毒性。总之，光在 TOrCs 的共代谢过程中起着至关重要的作用。
