Variation in the dehydrogenase (DH) activity and its simultaneous influence on hydrogen (H(2)) production, substrate degradation rate (SDR) and volatile fatty acid (VFA) generation was investigated with respect to varying poised potential in single chambered membrane-less microbial electrolysis cell (MEC) using anaerobic consortia as biocatalyst. Poised potential showed significant influence on H(2) production and DH activity. Maximum H(2) production was observed at 1.0 V whereas the control system showed least H(2) production among the experimental variations studied. DH activity was observed maximum at 0.6 V followed by 0.8, 0.9 and 1.0 V, suggests the influence of poised potential on the microbial metabolism. Almost complete degradation of substrate was observed in all the experimental conditions studied irrespective of the applied potential. Experimental data was also analysed employing multiple regression analysis and 3D-surface plots to find out the best theoretical poised potential for maximum H(2) production and DH activity. (C) 2011 Elsevier Ltd. All rights reserved.