Ethanol Induced Yeast Film Formation with Cell Surface Hydrophobicity as a Major Determinant
H. Alexandre, F. Bertrand, C. Charpentier
Enology laboratory, Institut Jules Guyot, Universitè de Bourgogne 21004 Dijon cedex
Received September 9, 1997
Accepted January 15, 1998
cell surface hydrophobicity, yeast film formation, film yeast, Saccharomyces cerevisiae (belicus, cheriensis, montuliensis)
In this study we have investigated the influence of ethanol on yeast film formation and cell surface hydrophobicity (CSH). A yeast strain (P3) previously isolated from film yeast was grown in a medium containing increasing ethanol concentration ranging from 0 to 14% (volume fraction). The growth of the film increased with higher concentration of ethanol up to 10%. We demonstrate for the first time using two different methods that ethanol induces an increase in cell surface hydrophobicity. Taking into account the increase in CSH with increasing ethanol concentration which leads to greater film development, it seems likely that CSH alteration constitutes an adaptation mechanism which allows the cell to rise to the surface where growth conditions are favoured, i.e. oxidative metabolism. The effect of CSH on yeast film formation has been confirmed using a wine strain (3079) able to form a film on the liquid surface. Thus we have shown that this yeast possesses a lower CSH (50%) compared with P3 strain (80%). However, CSH is not the only determinant of film formation since a respiratory deficient mutant (P3 rho-) with high cell surface hydrophobicity could not form a film. Treatment of cells with lylicase which dramatically reduced CSH, suggests the protein or glycoprotein nature of the component responsible for CSH.
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