Utilization and transport of acetic acid in Dekkera anomala and their implications on the survival of the yeast in acidic environments

The yeast Dekkera anomala IGC 5153 exhibited a restricted ability to use weak acids as the only carbon and energy sources. Of the monocarboxylic, dicarboxylic, and tricarboxylic acids tested, only acetic acid was used in such a way. The cells were able to grow at acetic acid concentrations of 0.1 to 3% (vol/vol) over a pH range of 3.5 to 5.5, and the specific growth rates decreased exponentially with the increase of the undissociated acetic acid concentration in the culture medium. Transport assays carried out in cells that exhibited higher specific growth rates showed the presence of an acetate-proton symport associated with a simple diffusion component of the undissociated acetic acid, the weight of the latter increasing with the undissociated acid concentration in the culture media. The acetate carrier was shared by propionic, formic, and sorbic acids and was inducible and repressed by glucose and concentrations of undissociated acetic acid in the culture medium above 0.3% (vol/vol). In undissociated acetic acid repression conditions, the lowest values for the yeast specific growth rates were obtained, and the simple diffusion of the undissociated acid was the only mechanism involved in the acetic acid uptake by the cells. The results will be discussed in terms of the high tolerance of D. anomala to the acidic stress conditions present in wine.