Civil and Environmental Engineering, University of Alberta, 9211-116 Street NW, Edmonton, AB, T6G 1H9, Canada.
Sci Rep. 2021 Apr 12;11(1):7933. doi: 10.1038/s41598-021-87118-w.
The microbial electrolysis cell assisted anaerobic digestion holds great promises over conventional anaerobic digestion. This article reports an experimental investigation of extracellular polymeric substances (EPS), reactive oxygen species (ROS), and the expression of genes associated with extracellular electron transfer (EET) in methanogenic biocathodes. The MEC-AD systems were examined using two cathode materials: carbon fibers and stainless-steel mesh. A higher abundance of hydrogenotrophic Methanobacterium sp. and homoacetogenic Acetobacterium sp. appeared to play a major role in superior methanogenesis from stainless steel biocathode than carbon fibers. Moreover, the higher secretion of EPS accompanied by the lower ROS level in stainless steel biocathode indicated that higher EPS perhaps protected cells from harsh metabolic conditions (possibly unfavorable local pH) induced by faster catalysis of hydrogen evolution reaction. In contrast, EET-associated gene expression patterns were comparable in both biocathodes. Thus, these results indicated hydrogenotrophic methanogenesis is the key mechanism, while cathodic EET has a trivial role in distinguishing performances between two cathode electrodes. These results provide new insights into the efficient methanogenic biocathode development.
微生物电解池辅助厌氧消化相对于传统厌氧消化具有很大的优势。本文报道了对产甲烷生物阴极中细胞外聚合物（EPS）、活性氧（ROS）和与细胞外电子传递（EET）相关基因表达的实验研究。使用两种阴极材料：碳纤维和不锈钢网来检查 MEC-AD 系统。似乎丰度更高的氢营养型甲烷杆菌和同型产乙酸菌在不锈钢生物阴极中比在碳纤维上具有更高的产甲烷能力。此外，不锈钢生物阴极中 EPS 的大量分泌伴随着较低的 ROS 水平，这表明较高的 EPS 可能保护细胞免受由更快的析氢反应催化引起的恶劣代谢条件（可能是不利的局部 pH 值）的影响。相比之下，两种生物阴极中的 EET 相关基因表达模式相似。因此，这些结果表明氢营养型产甲烷作用是关键机制，而阴极 EET 在区分两种阴极电极性能方面作用不大。这些结果为高效产甲烷生物阴极的开发提供了新的见解。
