Bioengineering and Environmental Sciences Lab, Department of Energy and Environmental Engineering, CSIR- Indian Institute of Chemical Technology, Hyderabad 500 007, India; Prof. Brien Holden Eye Research Centre, L V Prasad Eye Institute, Hyderabad 500 034, India.
Bioengineering and Environmental Sciences Lab, Department of Energy and Environmental Engineering, CSIR- Indian Institute of Chemical Technology, Hyderabad 500 007, India; Academy of Scientific and Innovative Research (AcSIR), CSIR-Indian Institute of Chemical Technology (CSIR-IICT) Campus, Hyderabad, India.
Bioelectrochemistry. 2020 Aug;134:107530. doi: 10.1016/j.bioelechem.2020.107530. Epub 2020 Apr 8.
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 H 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 H 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.
氧化还原电位是决定生物催化剂代谢途径命运及其在微生物电化学系统中相关产物合成的关键调节剂之一。在本研究中，使用分离的大肠杆菌 HP3 作为模型生物，以丙酮酸作为底物，研究了施加的电势对发酵产物和代谢通量的影响。为了深入了解代谢转变，构建了电发酵（EF）系统，并在阳极分别将氧化还原电位稳定在 0.2 V、0.4 V、0.6 V 和 0.8 V（相对于 Ag/AgCl）的正、负电位。除了循环伏安法和短链脂肪酸分析外，还通过相对表达编码乳酸脱氢酶（ldhA）、丙酮酸甲酸裂解酶（pflB）、丙酮酸脱氢酶（aceF）、氢化酶（hycE）和 NADH：氧化还原酶（nuoB）的基因，评估了代谢转变。结果表明，与对照相比，稳定条件对产物形成有显著影响，并观察到与丙酮酸代谢相关的关键酶的上调。具体而言，EF 在-0.8 V 和-0.2 V 下分别将 H2 产量提高了 7.9 倍和 5.3 倍，而在+0.8 V 下的操作使乳酸产量比对照提高了 1.9 倍。同时，在-0.8 V 下稳定运行时，参与 H2 生产途径的关键基因 plfB、hycE 和 nuoB 均显著上调，而在其他条件下则没有。同样，在+0.8 V 下稳定运行时，基因 ldhA 的转录本也显著上调。该研究阐明了氧化还原电位对产物形成的作用，以及与生物电化学特性相关的代谢途径中关键酶编码基因的相对表达。
