Abstract: The inhibitor tolerance of a xylose-fermenting industrial Saccharomyces cerevisiae strain was improved through direct acclimation or ultraviolet mutation combined with acclimation. During the repeated batch incubations,the concentration of the mixed inhibitors,containing nine kinds of typical inhibitors,was gradually increased to make cells adapt to the high inhibitor concentration. UV mutation combined with acclimation improved the tolerance of cells to inhibitors with high concentrations more effectively than direct acclimation. By the isolation and screening of mutation strains,three mutation strains with better inhibitor tolerance than the original strain were obtained. They showed 11.3%-23.2% higher xylose consumption ratios than the original strain when fermenting xylose under the inhibitory condition of 100% MI（formic acid 1 g/L,acetic acid 3.5 g/L,levulic acid 1.5 g/L,furfural 1.5 g/L,5-hydroxymethylfurfural（5-HMF）1.5 g/L,syringaldehyde 0.1 g/L,vanillin 0.1 g/L,coniferaldehyde 0.025 g/L,cinnamic acid 0.025 g/L）. UV mutation combined with acclimation improved the tolerance of S. cerevisiae strain to mixed inhibitors.

Key words: Saccharomyces cerevisiae, inhibitor tolerance, fuel ethanol, xylose utilization