Redox potential is one of the key regulators in determining the fate of the metabolic pathways of biocatalysts and of their associated product synthesis in microbial electrochemical systems. In the present study, the influence of applied potentials on fermentation products and metabolic flux was investigated using isolated E. coli HP3 as a model organism using pyruvate as a substrate. To provide insights into metabolic shifts, electro-fermentative (EF) systems were constructed and poised at both positive and negative redox potentials of 0.2 V, 0.4 V, 0.6 V and 0.8 V (vs Ag/AgCl) at the anode. The relative expression of genes encoding lactate dehydrogenase (ldhA), pyruvate formate lyase (pflB), pyruvate dehydrogenase (aceF), hydrogenase (hycE) and NADH: oxidoreductase (nuoB) enabled assessment of metabolic shifts in addition to cyclic voltammograms and short chain fatty acid profiling. Results showed that poised conditions had a significant effect on product formation and observed up-regulation of key enzymes involved in pyruvate metabolism in comparison to controls. More specifically, EF poised at -0.8 V and -0.2 V enhanced H2 production by 7.9 folds and 5.3 folds respectively, whilst at +0.8 V poised operation enhanced lactate production by 1.9 folds compared to the control. Concomitantly, the key genes involved in the pathway for H2 production viz., plfB, hycE and nuoB were all up-regulated significantly in a reactor poised at -0.8 V compared with other conditions. Similarly, transcripts for gene ldhA were up-regulated significantly in the system poised with +0.8 V. The study elucidated the role of redox potential on the product formation with respect to the relative expression of the genes encoding key enzymes in the metabolic pathway in correlation with bio-electrochemical characteristics.

中文翻译：

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监测由于微生物电化学系统中施加的电位而导致的大肠杆菌中的代谢途径改变。

在微生物电化学系统中，氧化还原电位是决定生物催化剂的代谢途径及其相关产物合成的命运的关键调节剂之一。在本研究中，使用丙酮酸作为底物，使用分离的大肠杆菌HP3作为模型生物，研究了施加电势对发酵产物和代谢通量的影响。为了提供对代谢变化的见解，构建了电发酵（EF）系统，并在阳极上分别设置了0.2 V，0.4 V，0.6 V和0.8 V（相对于Ag / AgCl）的正和负氧化还原电势。编码乳酸脱氢酶（ldhA），丙酮酸甲酸酯裂解酶（pflB），丙酮酸脱氢酶（aceF），氢化酶（hycE）和NADH的基因的相对表达：除循环伏安图和短链脂肪酸谱分析外，氧化还原酶（nuoB）还可以评估代谢变化。结果表明，与对照组相比，稳定的条件对产物形成具有显着影响，并且观察到丙酮酸代谢中涉及的关键酶的上调。更具体地，与对照相比，在-0.8V和-0.2V蓄积的EF分别将H 2产生增加了7.9倍和5.3倍，而在+ 0.8V蓄积操作中的EF将乳酸产生增加了1.9倍。同时，与其他条件相比，在-0.8 V的反应堆中，参与氢气产生途径的关键基因即plfB，hycE和nuoB均显着上调。同样，ldhA基因的转录本在+0.8 V的系统中也显着上调。