Formation of N-nitrosodimethylamine precursors through the microbiological metabolism of nitrogenous substrates in water
Formation of N-nitrosodimethylamine precursors through the microbiological metabolism of nitrogenous substrates in water
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通过水中含氮底物的微生物代谢形成 N-亚硝基二甲胺前体
DOI：
10.1016/j.watres.2020.116055
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发表时间：
2020
期刊：
影响因子：
12.8
通讯作者：
Chao Chen
中科院分区：
文献类型：
--
作者：
Er Bei;Xiao Li;Fuhua Wu;Shixiang Li;Xinsheng He;Yufang Wang;Yu Qiu;Yu Wang;Chengkun Wang;Jun Wang;Xiaojian Zhang;Chao Chen
N-亚硝基二甲胺 (NDMA) 作为一种新兴的消毒副产品，自 20 世纪 90 年代以来一直在全球范围内进行研究。然而，其主要前体仍不清楚。我们发现各种水样的NDMA形成电位（NDMAFP）在微生物培养过程中先升高后逐渐降低。我们假设NDMA前体可以通过含氮成分的代谢产生，然后逐渐被生物降解。为了验证这一假设，将六种氨基酸（AA）、蛋白胨和铵分别与微生物一起培养，并定期测量 NDMAFP。在有氧条件下，底物对 NDMAFP 的平均摩尔产率为 AA 的 60–200 × 10−6，蛋白胨的平均摩尔产率为 350 × 10−6。在蛋白胨实验中，分子量 (MW) 小于 1 k 道尔顿的细胞外部分对 NDMAFP 贡献最大，其次是 MW 在 10 k 至 0.22 μm 之间的细胞外部分和细胞内材料。实验期间检测到二甲胺和甲胺，但它们对 NDMAFP 的贡献相当有限。结果表明，亚硝胺前体可能不是AA或蛋白胨的直接代谢产物，而是活菌的排泄物或死菌体内的成分。我们的结果推断，在有氧条件下，AA 代谢可在水中产生 0.12 nmol/L（最大值）或 0.09 nmol/L（平均值）的 NDMAFP。根据 AA 代谢估算的 NDMAFP 可以占之前报道的中国水域 NDMAFP 中值 (0.32 nmol/L) 的 38%（最大值）或 27%（平均值）。
N-nitrosodimethylamine (NDMA) as one emerging disinfection by-product has been investigated globally since 1990s. However, its main precursors are still unclear. We found that NDMA formation potential (NDMAFP) of various water samples increased firstly and then decreased gradually during incubation with microorganism. We hypothesized that NDMA precursors could be produced through metabolism of nitrogenous components and then gradually be biodegraded. To verify this hypothesis, six amino acids (AAs), peptone and ammonium were separately incubated with microorganism and NDMAFP was measured regularly. The average molar yield of the substrates to NDMAFP were 60–200 × 10−6for the AAs, 350 × 10−6for peptone under aerobic condition. The extracellular fraction with molecular weight (MW) less than 1 k Dalton contributed the majority to NDMAFP in the peptone experiment, followed by that with MW between 10 k and 0.22 μm and the intracellular materials. Dimethylamine and methylamine were detected during the experiments but their contribution to NDMAFP is quite limited. The results indicate that the nitrosamine precursors may not be the direct metabolite of AAs or peptones but the excretion of living bacteria or the components in dead bacteria body. Our results inferred that AA metabolism may give an NDMAFP of 0.12 nmol/L (maximum) or 0.09 nmol/L (average) in water under aerobic condition. This estimation of NDMAFP from AA metabolism can account for 38% (maximum) or 27% (average) of the median NDMAFP in waters of China (0.32 nmol/L) reported before.