The Delta flo11/Delta flo11 disruptant strains constructed from three wild yeast strains, which were independently isolated from pellicles formed on the surface of contaminated stored wines, completely lost their ability to form pellicles. The FLO11 expression level of the pellicle-forming strains was much higher than that of non-pellicle-forming wine strains. Cell surface hydrophobicity of the Delta flo11/Delta flo11 disruptant strains was as high as that of the parental pellicle-forming strains. These findings indicate that FLO11 is essential for unfavorable pellicle formation of wild pellicle-forming yeasts by mechanisms other than increasing cell surface hydrophobicity. (C) 2010, The Society for Biotechnology, Japan. All rights reserved.