Investigating the specific role of external load on the performance versus stability trade-off in microbial fuel cells.

The performance and behavior of microbial fuel cells (MFCs) are influenced by among others the external load (R). In this study, the anode-surface biofilm formation in MFCs operated under different R selection/tracking-strategies was assessed. MFCs were characterized by electrochemical (voltage/current generation, polarization tests, EIS), molecular biological (microbial consortium analysis) and bioinformatics (principal component analysis) tools. The results indicated that the MFC with dynamic R adjustment (as a function of the actual MFC internal resistance) achieved notably higher performance but relatively lower operational stability, mainly due to the acidification of the biofilm. The opposite (lower performance, increased stability) could be observed with the static (low or high) R application (or OCV) strategies, where adaptive microbial processes were assumed. These possible adaptation phenomena were outlined by a theoretical framework and the significant impact of R on the anode colonization process and energy recovery with MFCs was concluded.