Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Xiao Ling Wei 200, Nanjing, Jiangsu 210094, China.
Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Xiao Ling Wei 200, Nanjing, Jiangsu 210094, China.
Water Res. 2024 Sep 15;262:122103. doi: 10.1016/j.watres.2024.122103. Epub 2024 Jul 14.
Nano zero-valent iron (NZVI) has been shown to effectively enhance the chain elongation (CE) process, addressing the issue of limited yield of medium-chain carboxylic acids (MCCA) from organic wastewater. However, the specific impact of NZVI on the metabolism of CE bacteria (CEB) is not well understood. In this study, it was aimed to investigate the mechanism by which an optimal concentration of NZVI influences CE metabolism, particularly in relation to ethanol oxidation, electron transfer, and MCCA synthesis. This was achieved through single-factor influence experiments and metagenomic analysis. The results showed that the addition of 1 g/gVSS NZVI achieved the highest MCCA yield (n-caproic acid + n-octanoic acid) at 2.02 g COD/L, which was 4.9 times higher than the control. This improvement in MCCA production induced by NZVI was attributed to several factors. Firstly, NZVI facilitated the oxidation of acetaldehyde, leading to its reduced accumulation in the system (from 18.4 % to 5.8 %), due to the optimized chemical environment created by NZVI corrosion, including near-neutral pH and a more reductive oxidation-reduction potential (ORP). Additionally, the inherent conductivity property of NZVI and the additional Fe ions released during corrosion improved the electron transfer efficiency between CEB. Lastly, both the composition of microbial communities and the abundance of unique enzyme genes confirmed the selective stimulation of NZVI on the reverse β-oxidation (RBO) pathway. These findings provide valuable insights into the role of NZVI in CEB metabolism and its potential application for enhancing MCCA production in CE bioreactors.
纳米零价铁（NZVI）已被证明可有效增强链伸长（CE）过程，解决了从有机废水中获得有限产量的中链羧酸（MCCA）的问题。然而，NZVI 对 CE 细菌（CEB）代谢的具体影响尚不清楚。在这项研究中，旨在研究 NZVI 以最佳浓度影响 CE 代谢的机制，特别是与乙醇氧化、电子转移和 MCCA 合成有关的机制。这是通过单因素影响实验和宏基因组分析来实现的。结果表明，添加 1 g/gVSS NZVI 可在 2.02 g COD/L 时获得最高的 MCCA 产量（正己酸+正辛酸），比对照提高了 4.9 倍。NZVI 诱导的 MCCA 产量提高归因于几个因素。首先，NZVI 促进了乙醛的氧化，由于 NZVI 腐蚀产生的优化化学环境，包括近中性 pH 和更还原的氧化还原电位（ORP），系统中乙醛的积累减少（从 18.4%减少到 5.8%）。此外，NZVI 的固有导电性和腐蚀过程中释放的额外 Fe 离子提高了 CEB 之间的电子传递效率。最后，微生物群落的组成和独特酶基因的丰度都证实了 NZVI 对反向β-氧化（RBO）途径的选择性刺激。这些发现为 NZVI 在 CEB 代谢中的作用及其在增强 CE 生物反应器中 MCCA 生产方面的潜在应用提供了有价值的见解。
