Microbial electrolysis is a promising technology for converting aqueous wastes into hydrogen. However, substrate adaptability is an important feature, seldom documented in microbial electrolysis cells (MECs). In addition, the correlation between substrate composition and community structure has not been well established. This study used an MEC capable of producing over 10 L/L-day of hydrogen from a switchgrass-derived bio-oil aqueous phase and investigated four additional substrates, tested in sequence on a mature biofilm. The additional substrates included a red oak-derived bio-oil aqueous phase, a corn stover fermentation product, a mixture of phenol and acetate, and acetate alone. The MECs fed with the corn stover fermentation product resulted in the highest performance among the complex feedstocks, producing an average current density of 7.3 ± 0.51 A/m2, although the acetate fed MECs outperformed complex substrates, producing 12.3 ± 0.01 A/m2. 16S rRNA gene sequencing showed that community structure and community diversity were not predictive of performance, and replicate community structures diverged despite identical inoculum and enrichment procedure. The trends in each replicate, however, were indicative of the influence of the substrates. Geobacter was the most dominant genus across most of the samples tested, but its abundance did not correlate strongly to current density. High-performance liquid chromatography (HPLC) showed that acetic acid accumulated during open circuit conditions when MECs were fed with complex feedstocks and was quickly degraded once closed circuit conditions were applied. The largest net acetic acid removal rate occurred when MECs were fed with red oak bio-oil aqueous phase, consuming 2.93 ± 0.00 g/L-day. Principal component analysis found that MEC performance metrics such as current density, hydrogen productivity, and chemical oxygen demand removal were closely correlated. Net acetic acid removal was also found to correlate with performance. However, no bacterial genus appeared to correlated to these performance metrics strongly, and the analysis suggested that less than 70% of the variance was accounted for by the two components. This study demonstrates the robustness of microbial communities to adapt to a range of feedstocks and conditions without relying on specific species, delivering high hydrogen productivities despite differences in community structure. The results indicate that functional adaptation may play a larger role in performance than community composition. Further investigation of the roles each microbe plays in these communities will help MECs to become integral in the 21st-century bioeconomy to produce zero-emission fuels.

中文翻译：

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在多种复杂原料上运行的微生物电解池的性能和群落结构动态


微生物电解是将水性废物转化为氢气的有前景的技术。然而，底物适应性是一个重要特征，但在微生物电解池（MEC）中很少有记录。此外，底物组成与群落结构之间的相关性尚未明确。这项研究使用了能够从柳枝稷衍生的生物油水相中生产超过 10 L/L 天氢气的 MEC，并研究了四种其他底物，并在成熟的生物膜上依次进行了测试。其他底物包括红橡树衍生的生物油水相、玉米秸秆发酵产物、苯酚和乙酸盐的混合物以及单独的乙酸盐。饲喂玉米秸秆发酵产物的 MEC 在复杂原料中表现出最高的性能，产生的平均电流密度为 7.3 ± 0.51 A/m2，尽管饲喂醋酸盐的 MEC 优于复杂基质，产生 12.3 ± 0.01 A/m2。 16S rRNA 基因测序表明，群落结构和群落多样性不能预测性能，尽管接种和富集程序相同，但复制群落结构存在差异。然而，每个重复的趋势表明了底物的影响。地杆菌属是大多数测试样本中最主要的属，但其丰度与电流密度没有很强的相关性。高效液相色谱 (HPLC) 显示，当 MEC 添加复杂原料时，乙酸会在开路条件下积累，一旦应用闭路条件，乙酸就会迅速降解。当 MEC 添加红橡生物油水相时，乙酸净去除率最大，每天消耗 2.93 ± 0.00 g/L。 主成分分析发现，电流密度、氢气生产率和化学需氧量去除等 MEC 性能指标密切相关。还发现乙酸净去除率与性能相关。然而，似乎没有细菌属与这些性能指标有很强的相关性，分析表明，这两个成分占不到 70% 的方差。这项研究证明了微生物群落在不依赖特定物种的情况下适应一系列原料和条件的稳健性，尽管群落结构存在差异，但仍能提供高氢生产率。结果表明，功能适应在性能方面可能比群落组成发挥更大的作用。进一步研究每种微生物在这些群落中所扮演的角色将有助于 MEC 成为 21 世纪生物经济中不可或缺的一部分，以生产零排放燃料。