The temperature effect on fermentative hydrogen (H-2) production from corn stover hydrolyzate was investigated under mesophilic (37 and 30 degrees C), thermophilic (55 degrees C), and extreme thermophilic (70 degrees C) conditions by using two typical seed sludges (activated sludge and anaerobic granular sludge). Among various temperatures, the fermentation at 55 degrees C reached the optimal H-2 production with the values of 6.08 mmol-H-2/g-utilized sugar for activated sludge and 7.74 mmol-H-2/g-utilized sugar for anaerobic granular sludge, respectively. For the two seed sludges, the effectiveness of fermentation temperature on H-2 production both followed the order as 55 degrees C > 70 degrees C > 37 degrees C approximate to 30 degrees C. The soluble metabolites composition at 55 degrees C showed the highest acetate and butyrate concentrations, as well as the minimum ethanol production, coinciding with better H-2-producing performances in these cases. Microbial community analysis indicated that microbial community diversity significantly decreased with increased fermentation temperature. Facultative anaerobes, such as Enterobacter spp., Klebsiella spp., and Citrobacter spp., were dominant in microbial community of the two seed sludges. As efficient H-2 producers, Bacillus sp. AB5283 in activated sludge and Thermoanaerobacterium sp. PO-2009 in anaerobic granular sludge might be mainly responsible for high H-2 yields under thermophilic condition. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.