Practical implementation of microbial fuel cell (MFC)-based power sources requires stable MFC performance regardless of the variations in the composition and quantity of a carbon source (fuel). This study describes a simple power management circuit (PMC) utilizing low and high voltage boundaries for intermittent MFC connection and disconnection to the electrical load. The PMC performance is demonstrated during MFC operation at carbon source-replete and carbon source-deplete conditions. In spite of MFC operation at external resistance values significantly below the estimated internal MFC resistance (e.g., 5.5 versus 24.5 Omega, respectively), the proposed PMC optimized MFC performance at all tested influent acetate concentrations, resulting in a volumetric power output of up to 56 mW center dot L-1. Furthermore, MFC operation with an up-converter is tested and approaches for optimizing the voltage boundaries are discussed. The robustness and simplicity of the proposed PMC algorithm allows for its implementation in a standalone microprocessor with ultralow energy consumption, which enables MFC application as an autonomous power source.