Abstract: Choosing hydrolyzate of poplar as fermentation material, which was obtained by two-step super-low acids hydrolysis, fuel ethanol production was studied by using Candida tropicalis 2.637 and Saccharomyces cerevisiae 2.699 respectively. Simul-taneously the influences to the ethanol yield by various pretreatment methods, such as Ca(OH)₂ neutralization, over-neutralization, active carbon adsorption and yeast-training were carried out. The experimental results show that C. tropicalis 2.637 is suitable to the first-step hydrolyzate rich in pentose to produce single cell protein. Yeast-training can improve fermentation speed and increase ethanol yield, especially to the second step hydrolyzate through which ethanol yield was increased from 14.45% to 39.37% by S. cerevisiae 2.699. The over-neutralization of hydrolyzate by Ca(OH)₂ improved ethanol yield, too. Therefore,for the hydrolysis of the first-step hydrolyzate, which contains mainly pentose and accompanied with hexose, more ethanol can be obtained by C. tropicalis 2.637 than by S. cerevisiae 2.699.

Key words: poplar, two-step super-low acids hydrolysis, fuel ethanol