Performance And Anode Bacterial Community Analysis In Different Substrates Powered Microbial Fuel Cell

Microbial fuel cells (MFCs) are devices that use bacteria as the catalysts to oxidize organic and inorganic matter and generate current. Parameters such as substrates used as fuels and the inoculum used for starting up the MFCs can influence the anode bacterial communities that establish in MFCs, which subsequently influence the efficiency of the MFCs. Therefore, further improvements might be achieved by understanding and engineering the microbial ecology at the anode, and community characterization in different substrates (especially real substrate) powered MFCs is a crucial starting point toward this objective.Electricity generation from wheat straw hydrolysate and the microbial ecology of electricity producing microbial communities developed in two-chamber MFC were investigated in this study. Maximum power density reached 123 mW/m² (364 mA/m²) with an organic loading of 1000 mg-COD/L hydrolysate as the electron donor. Power output exhibited saturation kinetics with respect to fuel concentration, with a predicted maximum power density of P_max = 152.2 mW/m² and half-saturation constant of K_s = 284.9 mg-COD/L, while Coulombic efficiency (CE) ranged from 15.5 to 37.1%. The main role of suspended bacteria was to ferment the complex fuel into simple fermentation products. The suspended bacteria found were different from the bacteria immobilized in the biofilm. Bacteria in the biofilm were consortia with sequences similar to Bacteroidetes (40% of sequences), Alphaproteobacteria (20%), Bacilli (20%), Deltaproteobacteria (10%), and Gammaproteobacteria (10%), while suspended community were dominated by Bacteroidetes (44.4% of sequences), Alphaproteobacteria (22.2%), Bacilli (22.2%), and Betaproteobacteria (11.2%).The co-effect of non-fermentable and fermentable substrates on the performance and microbial communities of MFC was also investigated in this study. When replaced the acetate by glucose as substrate in acetate powered MFC, the community composition was greatly changed, which subsequently decreased the efficiency of the MFC, the current can not be immediately produced unless 4 days later. When replaced the glucose by acetate as substrate in glucose powered MFC, the community composition was changed, which subsequently increased the efficiency of the MFC. Comparatively, the change of substrate (to acetate) in butyrate powered MFC has little effect on the community composition and power generation. The power generation in mixed substrates powered MFC was lower than single substrate powered MFC. Based on power generation and DGGE analysis, it can be concluded that the microbial community and power generation in fermentable substrate powered MFC was stable than other type substrates powered MFC.Electricity generation integrated with xylose degradation as well as the effect of FA on electricity production in microbial fuel cells (MFCs) was examined. Compared to control where FA was not added, addition of FA resulted in increase of power density and coulombic efficiency, which ranged from 8.3% to 56.7% and 20.5% to 33.5%, respectively. Presence of commercial FA in the anode chamber resulted in faster xylose degradation and formation of more oxidized products (acetate and formate) as well as less reduced products (ethanol) compared to the controls. Based on power generation and xylose degradation analysis, it can be concluded that FA can be used as a suitable redox mediator in MFC.