Niu Jianan, Kong Xin, Li Qingxia, Zhang Yongmei, Yuan Jin, Liu Jianguo, Zhang Yifeng
College of Environmental Science and Engineering, Taiyuan University of Technology, Jinzhong, 030600, China.
College of Environmental Science and Engineering, Taiyuan University of Technology, Jinzhong, 030600, China; School of Environment, Tsinghua University, Beijing, 100084, China; Department of Environmental and Resource Engineering, Technical University of Denmark, DK-2800, Lyngby, Denmark.
J Environ Manage. 2023 Jun 15;336:117686. doi: 10.1016/j.jenvman.2023.117686. Epub 2023 Mar 8.
Dosing zero valent iron (ZVI) or sodium hydroxide (NaOH) is the common method of addressing acidification in anaerobic digestion (AD) systems; however, few studies have discussed and compared their effects on microbial metabolism. In the present study, microbial syntrophy and metabolic pathways under ZVI and NaOH regulation are comparatively analyzed through microbial network analysis and metagenomic/metaproteomic analyses. CH yield in the ZVI reactor was 414 mL/gVS, an increase of 23% when compared with that in the reactor with NaOH dosing (336 mL/gVS). The methanogenesis recovery period in the ZVI reactor (37 days) was shorter than that in the NaOH reactor (48 days). Co-occurrence networks indicated that ZVI promoted Methanoculleus and Methanosarcina to establish a complex syntrophic association with SAO bacteria (Syntrophaceticus and Aminobacterium) and syntrophic acetogens (Syntrophomonas), strengthening SAO-hydrogenotrophic methanogenesis (HM) and acetoclastic methanogenesis (AM) pathways simultaneously. Metagenomic analysis showed that the relative abundance of mcrA and fwdB in the ZVI reactor was higher 27% than that in the NaOH reactor. Furthermore, through metaproteomics analysis, much more enzymes related to glucose degradation, bioconversion of butyric acid and pyruvate, conversion of formate and acetate to CO, and production of CH from acetate and CO were significantly upregulated under ZVI regulation than under NaOH regulation (fold change relative to control [FC] > 1.5, p < 0.05). The results of the present study enhance our understanding of methanogenic mechanisms under the regulation of ZVI, providing a theoretical basis for its practical application in AD systems experiencing VFA suppression.
投加零价铁（ZVI）或氢氧化钠（NaOH）是解决厌氧消化（AD）系统酸化问题的常用方法；然而，很少有研究讨论并比较它们对微生物代谢的影响。在本研究中，通过微生物网络分析以及宏基因组/宏蛋白质组分析，对ZVI和NaOH调控下的微生物互营作用和代谢途径进行了比较分析。ZVI反应器中的CH产量为414 mL/gVS，与投加NaOH的反应器（336 mL/gVS）相比增加了23%。ZVI反应器中的产甲烷恢复周期（37天）比NaOH反应器中的（48天）短。共现网络表明，ZVI促进了甲烷袋菌属和甲烷八叠球菌属与SAO细菌（乙酸互营菌属和氨基杆菌属）以及互营产乙酸菌（互营单胞菌属）建立复杂的互营共生关系，同时加强了SAO-氢营养型产甲烷（HM）和乙酸裂解产甲烷（AM）途径。宏基因组分析表明，ZVI反应器中mcrA和fwdB的相对丰度比NaOH反应器中的高27%。此外，通过宏蛋白质组分析，与葡萄糖降解、丁酸和丙酮酸的生物转化、甲酸盐和乙酸盐转化为CO以及乙酸盐和CO产生CH相关的更多酶在ZVI调控下比在NaOH调控下显著上调（相对于对照的倍数变化[FC] > 1.5，p < 0.05）。本研究结果加深了我们对ZVI调控下产甲烷机制的理解，为其在经历VFA抑制的AD系统中的实际应用提供了理论依据。
