Glucose electro-fermentation as main driver for efficient H₂-producing bacteria selection in mixed cultures

Electro-fermentation has been recently proposed as a new operational mode of bioprocess control using polarized electrodes. This paper aims to evaluate how polarized electrodes are affecting microbial metabolic fermentative pathways, with a special focus on how the bacterial populations are affected during hydrogen production by dark fermentation. Four different potentials were applied on the working electrode in batch electro-fermentation tests operated with mixed culture and using glucose as a substrate. Two different metabolic behaviours for H₂ production were observed in electro-fermentation. The first one led to a higher H₂ production compared to conventional fermentation with a strong selection of Clostridium sp. The second behaviour led to lower H₂ production along with ethanol, and strongly correlated with the selection of Escherichia and Enterobacter genera. However, the effect of the applied potential on population selection was mostly non-linear and no simple relationship was found between these two parameters. Overall, electro-fermentation process has shown its potential as a new type of control for mixed-culture bioprocesses with significant effects of polarized electrodes on glucose fermentation.