Brettanomyces as a polluting yeast in alcoholic fermentations: Study of its relations to Saccharomyces
2000
Strehaiano, Pierre | Alfenore, Sandrine | Oranut Phowchinda | Delia, Marie-Line(Laboratoire de Genie Chimique, UMR-CNRS 5503.ENSIGC-INP, 18 chemin de la Loge, 31 078 Toulouse Cedex 4 (France)_)
Brettanomyces strain was isolated from a polluted plant. Its identification was confirmed by I.H.E.M. (Belgium). The Saccharomyces yeast used was the strain Hirondelle bleue which is produced by Lessaffre S.A. The experiments were run using a synthetic medium with different concentrations of acetic acid (in a range between 0 and 6 g/L). The growth was measured by the optical density value (the relation to the dry weight of cells was previously done). In the case of mixed cultures, the cell count was made using an hematimeter, due to the differences in the cell size and morphology it was possible to distinguish Saccharomyces yeasts and Brettanomyces yeasts. The objective of this work was first to appreciate the true effect of the acetic acid on the growth of these two kinds of yeasts. The experiments were done under aerobiosis as well as under anaerobiosis. Also, different cultures (with different initial conditions) were carried out with Saccaromyces and Brettanomyces both together, and the behaviour of the culture was analyzed and compared to the behaviour of pure culture. It is clearly shown that the acetic acid acts the same on Saccharomyces and Brettanomyces when growing under anaerobiosis. But, under aerobiosis, Saccharomyces yeast growth is more inhibited, specially for low levels of acetic acid. Nevertheless, it seems difficult to attribute to the single acetic acid the wash-out of the Saccharomyces yeasts when Brettanomyces are growing, its level being only 0.5-1 g/L. Using mixed cultures, it is shown that the replacement of Saccharomyces yeast by Brettanomyces is possible only if this last one is in an active phase of growth and after the lag-phase.
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