Department of Civil, Construction, and Environmental Engineering, The University of Alabama, Tuscaloosa, AL 35487, USA.
Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
Water Res. 2024 Nov 15;266:122373. doi: 10.1016/j.watres.2024.122373. Epub 2024 Sep 2.
Glyphosate, the most widely used herbicide globally, is accumulating in the environment and poses significant potential eco- and bio-toxicity risks. While natural attenuation of glyphosate has been reported, the efficacy varies considerably and the dominant metabolite, aminomethylphosphonic acid (AMPA), is potentially more persistent and toxic. This study investigated the bioelectrochemical system (BES) for glyphosate degradation under anaerobic, reductive conditions. Atomistic simulations using density functional theory (DFT) predicted increased thermodynamic favorability for the non-dominant C-P lyase degradation pathway under external charge, which suppressed AMPA production. Experimental results confirmed that cathodic poised potential (-0.4 V vs. Ag/AgCl) enhanced glyphosate degradation (75 % in BES vs. ∼40 % in the control conditions after 37 days), and lowered the AMPA yield (0.52 mol AMPA yield per mol glyphosate removed in BES vs. 0.77-0.86 mol mol in the control conditions). Geobacter lovleyi was likely the active species driving the C-P lyase pathway, as evidenced by the increase of its relative abundance, the upregulation of its extracellular electron transfer genes (most notably mtr) and the up-regulation of its phnJ and hcp genes (encoding C-P layse and hydroxylamine reductase respectively).
草甘膦是全球应用最广泛的除草剂，在环境中不断积累，对生态和生物具有显著的潜在毒性风险。尽管草甘膦的自然衰减已被报道，但效果差异很大，且主要代谢物氨甲基膦酸（AMPA）可能更持久且毒性更大。本研究探讨了在厌氧、还原条件下生物电化学系统（BES）对草甘膦的降解作用。密度泛函理论（DFT）的原子模拟预测，在外加电荷下，非主导的 C-P 裂合酶降解途径的热力学稳定性增加，从而抑制 AMPA 的生成。实验结果证实，阴极偏置电位（-0.4 V 对 Ag/AgCl）增强了草甘膦的降解（BES 中 37 天后降解率为 75%，而对照条件下约为 40%），并降低了 AMPA 的生成量（BES 中每去除 1 摩尔草甘膦生成 0.52 摩尔 AMPA，而对照条件下为 0.77-0.86 摩尔）。证据表明，嗜地杆菌（Geobacter lovleyi）可能是驱动 C-P 裂合酶途径的活性物种，其相对丰度增加，细胞外电子转移基因（尤其是 mtr）上调，以及 phnJ 和 hcp 基因（分别编码 C-P 裂合酶和羟胺还原酶）上调。
