State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China; State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, PR China.
State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China.
Water Res. 2024 Sep 15;262:122125. doi: 10.1016/j.watres.2024.122125. Epub 2024 Jul 21.
Anaerobic digestion is an indispensable technical option towards green and low-carbon wastewater treatment, with interspecies electron transfer (IET) playing a key role in its efficiency and operational stability. The exogenous semiconductive iron oxides have been proven to effectively enhance IET, while the cognition of the physicochemical-biochemical coupling stimulatory mechanism was circumscribed and remains to be elucidated. In this study, semiconductive iron oxides, α-FeO, γ-FeO, α-FeOOH, and γ-FeOOH were found to significantly enhance syntrophic methanogenesis by 76.39, 72.40, 37.33, and 32.64% through redirecting the dominant IET pathway from classical interspecies hydrogen transfer to robust direct interspecies electron transfer (DIET). Their alternative roles as electron shuttles potentially substituting for c-type cytochromes were conjectured to establish an electron transport matrix associated with conductive pili. Distinguished from the conventional electron conductor mechanism of conductive FeO, semiconductive iron oxides facilitated DIET intrinsically through the capacitive Fe(III/II) redox cycles coupled with secondary mineralization. The growth of Aminobacterium, Sedimentibacter, and Methanothrix was enriched and the gene copy numbers of Geobacteraceae 16S ribosomal ribonucleic acid were selectively flourished by 2.0-∼4.5- fold to establish a favorable microflora for DIET pathway. Metabolic pathways of syntrophic acetogenesis from propionate/butyrate and CO reduction methanogenesis were correspondingly promoted. The above findings provide new insights into the underlying mechanism of iron minerals enhancing the DIET-oriented pathway and offer paradigms for redox-mediated energy harvesting biological wastewater treatment.
厌氧消化是实现绿色低碳废水处理不可或缺的技术选择，种间电子传递（IET）在其效率和运行稳定性方面发挥着关键作用。外源性半导体氧化铁已被证明能有效地增强 IET，而对其物理化学-生物化学耦合刺激机制的认识受到限制，仍有待阐明。在本研究中，半导体氧化铁 α-FeO、γ-FeO、α-FeOOH 和 γ-FeOOH 被发现通过将主要 IET 途径从经典的种间氢转移重定向到强大的直接种间电子转移（DIET），分别显著增强了共代谢产甲烷作用，增强幅度分别为 76.39%、72.40%、37.33%和 32.64%。它们作为电子穿梭体的替代作用，可能取代 c 型细胞色素，建立与导电菌毛相关的电子传递基质。与传统导电 FeO 的电子导体机制不同，半导体氧化铁通过电容 Fe(III/II)氧化还原循环与次生矿化内在地促进 DIET。Aminobacterium、Sedimentibacter 和 Methanothrix 的生长得到了富集，Geobacteraceae 16S 核糖体 rRNA 的基因拷贝数选择性地增加了 2.0-∼4.5-倍，为 DIET 途径建立了有利的微生物群落。丙酸/丁酸的共代谢产乙酸和 CO 还原产甲烷的代谢途径也相应得到了促进。上述发现为铁矿物增强 DIET 定向途径的潜在机制提供了新的见解，并为氧化还原介导的能量收获生物废水处理提供了范例。
