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 p. cent (v/v). It results from this study that up to 10 p. cent ethanol, the greater was the ethanol concentration, the greater was the growth of film. Using two different techniques (phase partition method, magnobead assay), we have shown that ethanol altered the CSH of the yeast. The measured hydrophobicity (p. cent) of cells grown without ethanol was 65 p. cent compared with 81 p. cent with 14 p. cent (v/v) ethanol. 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 oxydative metabolism. The role of CSH on yeast film formation was sustained by using a wine strain (3079) enable to form a film on the liquid surface, thus we have shown that this yeast possess a lower CSH (50 p. cent) compared to P3 strain (80 p. cent). However, CSH is not the only determinant for film formation since a respiratory deficient mutant (P3 rho-) with high cell surface hydrophobicity (80 p. cent) could not form a film. Treatment of cells with lyticase which dramatically reduced CSH of P3 strain from 80 to 15 p. cent points out the protein or glycoprotein nature of the component responsible for CSH.
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