Biological and Environmental Sciences and Engineering Division, Water Desalination and Reuse Research Center, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA, USA.
Appl Microbiol Biotechnol. 2016 Jul;100(13):5999-6011. doi: 10.1007/s00253-016-7402-2. Epub 2016 Mar 3.
Microbial electrolysis cells (MECs) provide a viable approach for bioenergy generation from fermentable substrates such as propionate. However, the paths of electron flow during propionate oxidation in the anode of MECs are unknown. Here, the paths of electron flow involved in propionate oxidation in the anode of two-chambered MECs were examined at low (4.5 mM) and high (36 mM) propionate concentrations. Electron mass balances and microbial community analysis revealed that multiple paths of electron flow (via acetate/H2 or acetate/formate) to current could occur simultaneously during propionate oxidation regardless of the concentration tested. Current (57-96 %) was the largest electron sink and methane (0-2.3 %) production was relatively unimportant at both concentrations based on electron balances. At a low propionate concentration, reactors supplemented with 2-bromoethanesulfonate had slightly higher coulombic efficiencies than reactors lacking this methanogenesis inhibitor. However, an opposite trend was observed at high propionate concentration, where reactors supplemented with 2-bromoethanesulfonate had a lower coulombic efficiency and there was a greater percentage of electron loss (23.5 %) to undefined sinks compared to reactors without 2-bromoethanesulfonate (11.2 %). Propionate removal efficiencies were 98 % (low propionate concentration) and 78 % (high propionate concentration). Analysis of 16S rRNA gene pyrosequencing revealed the dominance of sequences most similar to Geobacter sulfurreducens PCA and G. sulfurreducens subsp. ethanolicus. Collectively, these results provide new insights on the paths of electron flow during propionate oxidation in the anode of MECs fed with low and high propionate concentrations.
微生物电解池（MEC）为从可发酵基质（如丙酸）中产生生物能源提供了一种可行的方法。然而，MEC 阳极中丙酸氧化过程中的电子流动途径尚不清楚。在这里，在低（4.5 mM）和高（36 mM）丙酸浓度下，研究了两室 MEC 阳极中丙酸氧化过程中的电子流动途径。电子质量平衡和微生物群落分析表明，无论测试的浓度如何，丙酸氧化过程中可能同时发生多种电子流途径（通过乙酸盐/H2 或乙酸盐/甲酸盐）到电流。根据电子平衡，电流（57-96%）是最大的电子汇，甲烷（0-2.3%）的产生在这两种浓度下相对不重要。在低丙酸浓度下，添加 2-溴乙磺酸盐的反应器比没有添加这种甲烷生成抑制剂的反应器具有略高的库仑效率。然而，在高丙酸浓度下观察到相反的趋势，添加 2-溴乙磺酸盐的反应器的库仑效率较低，与没有添加 2-溴乙磺酸盐的反应器相比，电子损失（23.5%）到未定义的汇的比例更大（11.2%）。丙酸去除效率分别为 98%（低丙酸浓度）和 78%（高丙酸浓度）。16S rRNA 基因焦磷酸测序分析表明，序列与 Geobacter sulfurreducens PCA 和 G. sulfurreducens subsp. ethanolicus 最为相似，占主导地位。总的来说，这些结果为低浓度和高浓度丙酸进料的 MEC 阳极中丙酸氧化过程中的电子流动途径提供了新的见解。
