A new strain FS3 which could achieve an efficient bioconversion of raw corn stalk to hydrogen had been isolated from anaerobic acclimated sludge, and identified as Clostridium butyricum on the basis of a series of physiological and biochemical experiments and 16S rDNA gene sequence. The strain could utilize various carbon sources to produce hydrogen. On the basis of single-factor experiments, the response surface methodology (RSM) was performed to optimize the media for hydrogen production. The maximum hydrogen yield of 92.9 ml/g was observed under the optimal conditions: 20 g/l raw corn stalk, 1.76 g/l NH4HCO3, 0.91 g/l KH2PO4 and 10.4 ml/l nutrient solution. This finding opens a new avenue for direct conversion of raw cellulosic biomass to bio-hydrogen. (C) 2014 Elsevier Ltd. All rights reserved.