Ethanol production from lignocelluloses is a promising alternative liquid biofuel for sustainable energy supply.As the second abundant monosaccharide,xylose metabolism pathway needs to be introduced in Saccharomyces cerevisiae to improve the efficiency of lignocelluloses ethanol production.Heterologous expression of xylose isomerase (XI) is considered as an effective strategy to establish the xylose metabolic pathway in S.cerevisiae, since the converting of xylose to xylulose catalyzed by XI is cofactor-independent and not coupling xylitol formation.