In microbial fuel cells, electricity generation is assumed by bacterial degradation of low-grade organics generating electrons that are transferred to an electrode. The nature and efficiency of the electron transfer from the bacteria to the electrodes are determined by several chemical, physical and biological parameters. Specifically, the application of a specific potential at the bioanode has been shown to stimulate the formation of an electro-active biofilm, but the underlying mechanisms remain poorly understood. In this study, we have investigated the effect of an applied potential on the formation and electroactivity of biofilms established by Shewanella oneidensis bacteria on graphite felt electrodes in single- and double-chamber reactor configurations in oxic conditions. Using amperometry, cyclic voltammetry, and OCP/Power/Polarization curves techniques, we showed that a potential ranging between − 0.3 V and + 0.5 V (vs. Ag/AgCl/KCl sat.) and its converse application to a couple of electrodes leads to different electrochemical behaviors, anodic currents and biofilm architectures. For example, when the bacteria were confined in the anodic compartment of a double-chamber cell, a negative applied potential (− 0.3 V) at the bioanode favors a mediated electron transfer correlated with the progressive formation of a biofilm that fills the felt porosity and bridges the graphite fibers. In contrast, a positive applied potential (+ 0.3 V) at the bioanode stimulates a direct electron transfer resulting in the fast-bacterial colonization of the fibers only. These results provide significant insight for the understanding of the complex bacteria-electrode interactions in microbial fuel cells.

在微生物燃料电池中，通过低级有机物的细菌降解来产生电力，这些低级有机物会产生电子并转移到电极上。电子从细菌到电极的转移的性质和效率取决于几个化学，物理和生物学参数。具体而言，在生物阳极上施加特定电势已显示出刺激了电活性生物膜的形成，但其潜在机理仍知之甚少。在这项研究中，我们已经研究了施加的电势对拟南芥（Shewanella oneidensis）建立的生物膜形成和电活性的影响。在有氧条件下，单腔和双腔反应器配置中的石墨毡电极上的细菌。使用电流分析法，循环伏安法和OCP /功率/极化曲线技术，我们发现电势范围为-0.3 V至+ 0.5 V（vs。Ag / AgCl / KCl饱和），并将其相反地应用于一对电极引线应对不同的电化学行为，阳极电流和生物膜结构。例如，当细菌被限制在双室细胞的阳极室中时，在生物阳极处的负施加电势（-0.3 V）促进了介导的电子转移，该电子转移与逐步形成填充毛毡孔隙的生物膜有关。桥接石墨纤维。相反，施加的电位为正（+ 0。生物阳极处的3 V）刺激直接电子转移，仅导致纤维的快速细菌定殖。这些结果为理解微生物燃料电池中复杂的细菌-电极相互作用提供了重要的见识。