Bio-hydrogen produced from acetic acid steam-exploded corn straw (ASCS) by simultaneous saccharification and fermentation (SSF) with Ethanoligenes harbinense 49. The effects of acetic acid concentration and enzyme loading were investigated with respect to the maximum specific hydrogen production rate and hydrogen productivity. The hydrogen yield increased with increasing of acetic acid concentration, increased and then decreased with increasing of enzyme loading. The effect of enzyme loading for hydrogen production was more crucial than that of the acetic acid concentration. At acetic acid concentration of 16% and enzyme loading of 120 and 180 U/g, the maximum hydrogen yield and maximum specific hydrogen production rate was 72 ml/g ASCS and 103 ml/g VSS . d, respectively. Copyright (C) 2009 John Wiley & Sons, Ltd.