In the present study, the effect of sulfate on the hydrogen production from the organic fraction of municipal solid (OFMSW) waste using co-culture of Enterobacter aerogenes and E. coli has been studied under varying pH conditions. The presence of sulfate in the feedstock declines hydrogen production efficiency. To evaluate the effect of sulfate on hydrogen production from OFMSW, COD/sulfate ratio of 17.5, 15.0, 12.5, 10.0, 7.5, 5.0 and 2.5 were applied at different pH conditions (i.e. pH 5.5, 6.0 and 6.5). The hydrogen production continuously declined with the decreasing COD/sulfate ratio and increase in pH. The cumulative hydrogen production decreased from 220.8 +/- 10.5 mL in control to a minimum of 98.3 +/- 10.5 mL, 74.4 +/- 10.4 mL, and 44.6 +/- 2.6 mL at pH 5.5, 6.0 and 6.5 respectively. The major content of gaseous composition included hydrogen and CO2 at higher COD/sulfate ratio and low pH, while H2S formation started with the decrease in COD/sulfate ratio and increase in the pH. Similarly, sulfate removal efficiency was found to be influenced by COD/sulfate ratio and pH condition. Soluble metabolite analysis revealed that total volatile fatty acid concentration was not affected by sulfate addition. Thus, Sulfate removal is essential prior to fermentation in order to improve hydrogen yield. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.