Abstract
Shear stress is an important factor that affects the formation and structure of anode biofilms, which are strongly related to the extracellular electron transfer phenomena and bioelectric performance of bioanodes. Here, we show that using nitrogen sparging to induce shear stress during anode biofilm formation increases the linear sweep voltammetry peak current density of the mature anode biofilm from 2.37 ± 0.15 to 4.05 ± 0.25 A/m2. Electrochemical impedance spectroscopy results revealed that the shear-stress-enriched anode biofilm had a low charge transfer resistance of 46.34 Ω compared to that of the unperturbed enriched anode biofilm (72.2 Ω). Confocal laser scanning microscopy observations showed that the shear-stress-enriched biofilms were entirely viable, whereas the unperturbed enriched anode biofilm consisted of a live outer layer covering a dead inner-core layer. Based on biomass and community analyses, the shear-stress-enriched biofilm had four times the biofilm density (136.0 vs. 27.50 μg DNA/cm3) and twice the relative abundance of Geobacteraceae (over 80 vs. 40%) in comparison with those of the unperturbed enriched anode biofilm. These results show that applying high shear stress during anode biofilm enrichment can result in an entirely viable and dense biofilm with a high relative abundance of exoelectrogens and, consequently, better performance.
Highlights
Anodic microorganisms in microbial electrochemical systems (MESs) are biocatalysts that oxidize organic matter to transfer electrons to an electrode (Xiao et al, 2015; Hodgson et al, 2016)
The electrochemical impedance spectroscopy (EIS) results (Figure 3) showed that the increased anode performance of the Microbial Fuel Cells (MFCs) with shear-stress-enriched anode biofilms was mainly due to their lower charge transfer resistances, indicating that the change in Rct caused by the change in the anode biofilm structure is the key factor affecting anode performance
The observed anode biofilm structures that could affect Rct were considered as three different factors: the viability structure, the physical structure and the microbial community structure
Summary
Anodic microorganisms in microbial electrochemical systems (MESs) are biocatalysts that oxidize organic matter to transfer electrons to an electrode (Xiao et al, 2015; Hodgson et al, 2016). It has been found that several factors can affect the formation, structure, and performance of anode biofilms, including the substrate concentration (Hari et al, 2017), electron acceptor (Ucar et al, 2017), anode solution (Liu et al, 2017), electrode potential (Bosire and Rosenbaum, 2017), and electric field intensity (Du et al, 2018). The shear stress that arises from solution disturbance is an important factor affecting the formation, structure and performance of anode biofilms because of the physical force exerted on the anode biofilm and enhanced substance diffusion (substrate and metabolic end products). Enhanced substance diffusion [either the substrate or metabolic end products (H+)] can increase the biomass, viability and performance of the anode biofilm. We found that aerobically enriched anode biofilms with sufficient substance diffusion in the inner layer had a thicker inner layer and a higher current generation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
