A biological hydrogen-producing System is configured through Coupling ail electricity-assisting microbial fuel cell (MFC) with a hydrogen-producing Microbial electrolysis cell (MEC). The advantage of this biocatalyzed system is the in-situ utilization of the electric energy generated by ail MFC for hydrogen Production in ail MEC without external power Supply. In this Study, it is demonstrated that the hydrogen production in Such ail MEC-MFC-coupled system can be manipulated through adjusting the power input on the MEC. The power input of the MEC is regulated by applying different loading resistors connected into the circuit in series. When the loading resistance changes from 10 Omega to 10k Omega, the circuit current and volumetric hydrogen production rate varies in a range of 78 +/- 12 to 9 +/- 0 mA m(-2) and 2.9 +/- 0.2 to 0.2 +/- 0.0 mLL(-1) d(-1), respectively. The hydrogen recovery (R-H2), Coulombic efficiency (CE), and hydrogen yield (Y-H2) decrease with the increase in loading resistance. Thereafter, in order to acid power supply for hydrogen production in the MEC, additional one or two MFCs are introduced into this coupled system. When the MFCs are connected in series, File hydrogen production is significantly enhanced. In comparison, the parallel connection slightly reduces the hydrogen production. Connecting several MFCs in series is able to effectively increase power supply for hydrogen production, and has a potential to he used as a strategy to enhance hydrogen production in the MEC-MFC-coupled system from wastes. (C) 2009 Published by Elsevier B.V.