Cao Jiachang, Xu Ying, Zhang Chen, Li Xiang, Liu Rui, Wang Xueye, Dai Xiaohu
State Key Laboratory of Water Pollution Control and Green Resource Recycling, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
State Key Laboratory of Water Pollution Control and Green Resource Recycling, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
Water Res. 2025 Sep 15;284:124047. doi: 10.1016/j.watres.2025.124047. Epub 2025 Jun 18.
Water is widely present in sewage sludge, in which it constitutes the largest proportion; however, its participation in the methanogenesis of sludge has been overlooked. Here we revealed the mechanisms enhancing the participation of water in methanogenesis of sludge. Through stable isotope tracing experiments, we observed that isoelectric point pretreatment significantly enhanced the participation of water in CO-reduction methanogenesis. Experimental results show that solid-liquid non-covalent interactions and interfacial water ordering in sludge were significantly enhanced. The former outcome drove electron transfer, while the latter provided an efficient proton channel. Combined with hydrogen/deuterium kinetic isotope effect (KIE) tests, it demonstrated that the water-mediated proton-coupled electron transfer (PCET) in the sludge were enhanced, accompanied by possible quantum tunnelling effect (KIE >> 10). Variations in the concentrations of key enzymes indicated that enhancing water-mediated PCET promoted both intracellular and extracellular electron-proton flow and accelerated the efficiency of mutual conversion between NADH and NAD, strongly driving ATP synthesis. Further genome-centric metagenomic analysis and reaction thermodynamic calculations revealed that enhancing water-mediated PCET triggered enrichment of CO-reduction methanogenic consortia and effectively bypassed the limitation of H partial pressure, providing a thermodynamic advantage to promote collaborative methanogenic metabolisms. These findings provide a theoretical basis for regulating the methanogenesis of perishable organic solid waste by water.
水广泛存在于污水污泥中，占比最大；然而，其在污泥产甲烷过程中的作用一直被忽视。在此，我们揭示了增强水参与污泥产甲烷的机制。通过稳定同位素示踪实验，我们观察到等电点预处理显著增强了水在CO还原产甲烷过程中的参与度。实验结果表明，污泥中的固液非共价相互作用和界面水有序性显著增强。前者促进了电子转移，后者提供了高效的质子通道。结合氢/氘动力学同位素效应（KIE）测试，结果表明污泥中由水介导的质子耦合电子转移（PCET）增强，伴随着可能的量子隧穿效应（KIE >> 10）。关键酶浓度的变化表明，增强水介导的PCET促进了细胞内和细胞外的电子-质子流动，加速了NADH和NAD之间的相互转化效率，有力地推动了ATP合成。进一步的以基因组为中心的宏基因组分析和反应热力学计算表明，增强水介导的PCET引发了CO还原产甲烷菌群的富集，并有效绕过了H分压的限制，为促进协同产甲烷代谢提供了热力学优势。这些发现为通过水调控易腐有机固体废物的产甲烷过程提供了理论依据。
