Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, 9000, Ghent, Belgium.
Appl Microbiol Biotechnol. 2014 Apr;98(7):3205-17. doi: 10.1007/s00253-013-5328-5. Epub 2013 Nov 8.
Methane (CH4) release from wetlands is an important source of greenhouse gas emissions. Gas exchange occurs mainly through the aerenchyma of plants, and production of greenhouse gases is heavily dependent on rhizosphere biogeochemical conditions (i.e. substrate availability and redox potential). It is hypothesized that by introducing a biocatalyzed anode electrode in the rhizosphere of wetland plants, a competition for carbon and electrons can be invoked between electrical current-generating bacteria and methanogenic Archaea. The anode electrode is part of a bioelectrochemical system (BES) capable of harvesting electrical current from microbial metabolism. In this work, the anode of a BES was introduced in the rhizosphere of rice plants (Oryza sativa), and the impact on methane emissions was monitored. Microbial current generation was able to outcompete methanogenic processes when the bulk matrix contained low concentrations of organic carbon, provided that the electrical circuit with the effective electroactive microorganisms was in place. When interrupting the electrical circuit or supplying an excess of organic carbon, methanogenic metabolism was able to outcompete current generating metabolism. The qPCR results showed hydrogenotrophic methanogens were the most abundant methanogenic group present, while mixotrophic or acetoclastic methanogens were hardly detected in the bulk rhizosphere or on the electrodes. Competition for electron donor and acceptor were likely the main drivers to lower methane emissions. Overall, electrical current generation with BESs is an interesting option to control CH4 emissions from wetlands but needs to be applied in combination with other mitigation strategies to be successful and feasible in practice.
湿地中的甲烷（CH4）释放是温室气体排放的一个重要来源。气体交换主要通过植物的通气组织进行，而温室气体的产生则严重依赖于根际生物地球化学条件（即基质可用性和氧化还原电位）。据推测，通过在湿地植物的根际引入生物催化阳极电极，可以在电流产生细菌和产甲烷古菌之间引发对碳和电子的竞争。阳极电极是生物电化学系统（BES）的一部分，能够从微生物代谢中获取电流。在这项工作中，将 BES 的阳极引入水稻（Oryza sativa）植物的根际，并监测对甲烷排放的影响。当基质中含有低浓度的有机碳时，微生物电流的产生能够在很大程度上胜过产甲烷过程，只要与有效电活性微生物的电路保持畅通。当中断电路或供应过量的有机碳时，产甲烷代谢就能够胜过电流生成代谢。qPCR 结果表明，氢营养型产甲烷菌是存在的最丰富的产甲烷菌群，而混合营养型或乙酸营养型产甲烷菌在根际基质或电极上几乎检测不到。电子供体和受体的竞争可能是降低甲烷排放的主要驱动力。总的来说，BES 产生电流是控制湿地 CH4 排放的一种有趣选择，但需要与其他缓解策略结合使用，才能在实践中取得成功和可行。
