Using Acetate and Formate as the Substrates for Geobacter sulfurreducens Exoelectrogenesis Resulted in Different Half-saturation Potentials

• Published in: Denki kagaku oyobi kōgyō butsuri kagaku Vol. 83; no. 8; p. 600
• Main Authors: PENG, Luo, ZHANG, Xiao-Ting, KAWAICHI, Satoshi, XIE, De-Ti, LI, Zhen-Lun
• Format: Journal Article
• Language: Japanese
• Published: 2015
• Subjects: Acetates; Anodizing; Bacteria; Biofilms; Conduits; Electrodes; Formates; Reductases
• ISSN: 1344-3542
• DOI: 10.5796/electrochemistry.83.600

In bioelectrochemical systems where the oxidative current is mediated by microorganisms, it remains unexplored as to whether low-potential substrates (e.g. formate) enable the anode to work at lower potentials. Due to implications to relevant engineering and natural systems, this study evaluated such possibility and underlying causes. The investigation compared voltammograms of the model exoelectrogen (to exclude the interfering factors in undefined cultures) Geobacter sulfurreducens grown with acetate and formate. G. sulfurreducens had an EM (half-saturation potential) of -0.138 plus or minus 0.004 V vs. SHE when consuming acetate; an EM of -0.160 plus or minus 0.002 V when utilizing formate. Such variation usually requires alternation in electrode reductase expressed by bacteria, according to the existing Nernst-Monod model with a single species of electron conduit. For both acetate- and formate-grown biofilm, non-catalytic voltammetries found multiple redox couples with distinct formal potentials. No clear evidence could support a hypothesis that the bacteria synthesized any different electron conduits when the substrate was changed. Significant changes in the relative abundance of high-potential and low-potential electrocatalytically active conduits were not observed as well. However, low-potential conduits showed elevated electrocatalytic activities in the formate-grown biofilm, which might induce the shift in apparent EM.