Abstract
The anodic current production of Shewanella oneidensis MR-1 is typically lower compared to other electroactive bacteria. The main reason for the low current densities is the poor biofilm growth on most anode materials. We demonstrate that the high current production of Shewanella oneidensis MR-1 with electrospun anodes exhibits a similar threshold current density as dense Geobacter spp biofilms. The threshold current density is a result of local acidification in the biofilm. Increasing buffer concentration from 10 to 40 mM results in a 1.8-fold increase of the current density [(590 ± 25) μA cm−2] while biofilm growth stimulation by riboflavin has little effect on the current production. The current production of a reference material below the threshold did not respond to the increased buffer concentration but could be enhanced by supplemented riboflavin that stimulated the biofilm growth. Our results suggest that the current production with S. oneidensis is limited (1) by the biofilm growth on the anode that can be enhanced by the choice of the electrode material, and (2) by the proton transport through the biofilm and the associated local acidification.
Highlights
As the juggernaut of climate change is bearing down on mankind, potentially carbon neutral technologies, such as bioelectrochemical systems (BES) have become paramount for rescuing the planet
We investigate the effect of local acidification on the current production of MR-1/electrode composites using varying buffer concentrations
We investigated the current response to varying abundance of MR-1 cells, electron source, riboflavin, and local acidification
Summary
As the juggernaut of climate change is bearing down on mankind, potentially carbon neutral technologies, such as bioelectrochemical systems (BES) have become paramount for rescuing the planet. Shewanella oneidensis MR-1 (MR-1) and derived genetically engineered strains can serve as catalyst for various BES applications, e.g., CO2 fixation (Le et al, 2018; La Cava et al, 2020), electrode assisted fermentation to broaden the product spectrum of conventional fermentation (Bursac et al, 2017; Förster et al, 2017), and power generation (Biffinger et al, 2008). In these processes, high current densities are required for compact and cost-efficient production units.
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