In the present study two identical two-chamber microbial electrolysis cells (MECs), fed with an acetate synthetic medium, were used for hydrogen production, using different anodic materials, i.e. commercial carbon fiber paper (CP) and graphite granules (GG). The effects of the applied voltage (i.e. 0.7 and 0.9 V) and of the acclimation procedure (direct potentiostatic operation as MEC or galvanostatic as microbial fuel cell, MFC) were assessed and the performance of both MECs was compared in terms of their biochemical and electrochemical characteristics.