Bioelectrochemical Stimulation of Electromethanogenesis at a Seawater-Based Subsurface Aquifer in a Natural Gas Field
Bioelectrochemical Stimulation of Electromethanogenesis at a Seawater-Based Subsurface Aquifer in a Natural Gas Field
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DOI：
10.3389/fenrg.2018.00144
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发表时间：
2019-01
影响因子：
3.4
通讯作者：
S. Ishii;H. Imachi;K. Kawano;D. Murai;Miyuki Ogawara;Katsuyuki Uemastu;K. Nealson;F. Inagaki
中科院分区：
文献类型：
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作者：
S. Ishii;H. Imachi;K. Kawano;D. Murai;Miyuki Ogawara;Katsuyuki Uemastu;K. Nealson;F. Inagaki
在地下缺氧环境中，微生物群落通常产生甲烷作为消耗有机化合物的最终产物。这种代谢功能是沿海天然气含水层、海底泥火山和甲烷水合物中生物甲烷的来源。在产甲烷菌群中，氢营养型产甲烷菌和互养型细菌通过种间氢转移将挥发性脂肪酸互养转化为甲烷。最近，发酵/互养细菌和电养产甲烷菌之间的直接种间电子转移（DIET）已被提出作为一种有效的种间代谢物转移过程，以提高甲烷产量。在这项研究中，为了刺激的DIET相关的产甲烷过程在深层生物圈含水层系统中的天然气田，我们操作的生物电化学系统（BES）的阳极和阴极之间施加电压。两个单室BES填充有从陆上天然气井收集的基于海水的地层水，用乙酸盐反复修正，并在电极之间以600 mV操作21个月，导致乙酸盐通过电流消耗成功转化为甲烷。一个反应器产生稳定电流约200 mA/m2，库仑效率（CE）>90%;然而，另一个反应器，偶然断开3天，显示出较低的电产甲烷活性，CE仅为约10%。基于16 S rRNA基因的群落分析表明，产甲烷古菌家族Methanocalculaceae和Methanobacteriaceae在阴极生物膜中含量丰富，主要由单细胞层生物膜覆盖，表明它们是电产甲烷的关键参与者。相比之下，家族Methanosaetaceae在两个电极和电解质悬浮液中都是丰富的，仅在具有较少电产甲烷的反应器中，这表明该家族不参与电产甲烷，并且仅在无电子流事件后被激活。在阳极上，脱硫单胞菌科（Desulfuronadaceae）在运行初期占优势，而地杆菌科（Geobacteraceae）（主要是地碱杆菌属（Geoalkalibacter））在长期运行中出现的频率增加，表明这些科与电极呼吸反应有关。这些结果表明，具有电压施加的BES反应器有效地激活了天然气田中的地下DIET相关的产甲烷微生物组，并且在阳极和/或阴极生物膜内鉴定了特定的产电细菌和产电甲烷古菌。
In subsurface anoxic environments, microbial communities generally produce methane as an end-product to consume organic compounds. This metabolic function is a source of biogenic methane in coastal natural gas aquifers, submarine mud volcanoes and methane hydrates. Within the methanogenic communities, hydrogenotrophic methanogens and syntrophic bacteria are converting volatile fatty acids to methane syntrophically via interspecies hydrogen transfer. Recently, direct interspecies electron transfer (DIET) between fermentative/syntrophic bacteria and electrotrophic methanogens has been proposed as an effective interspecies metabolite transfer process to enhance methane production. In this study, in order to stimulate the DIET-associated methanogenic process at deep biosphere-aquifer systems in a natural gas field, we operated a bioelectrochemical system (BES) to apply voltage between an anode and a cathode. Two single-chamber BESs were filled with seawater-based formation water collected from an onshore natural gas well, repeatedly amended with acetate, and operated with 600 mV between electrodes for 21 months, resulting in a successful conversion of acetate to methane via electrical current consumption. One reactor yielded a stable current by ~200 mA/m2 with a coulombic efficiency (CE) of >90%; however, the other reactor, which had been incidentally disconnected for 3 days, showed less electromethanogenic activity with a CE of only ~10%. The 16S rRNA gene-based community analyses showed that two methanogenic archaeal families, Methanocalculaceae and Methanobacteriaceae, were abundant in cathode biofilms that were mainly covered by single-cell-layered biofilm, implicating them as key players in the electromethanogenesis. In contrast, family Methanosaetaceae was abundant at both electrodes and the electrolyte suspension only in the reactor with less electromethanogenesis, suggesting this family was not involved in electromethanogenesis and only activated after the no electron flow event. On anodes covered by thick biofilms with filamentous networks, family Desulfuromonadaceae dominated in the early stage of the operation, while family Geobacteraceae (mainly genus Geoalkalibacter) increased their frequencies during the longer-term operation, which indicates that these families were correlated with electrode-respiring reactions. These results indicate that the BES reactors with voltage application effectively activated a subsurface DIET-related methanogenic microbiome in the natural gas field, and specific electrogenic bacteria and electromethanogenic archaea were identified within the anode and/or cathode biofilms.