At the
pH optimum for fermentation (5.5±6.0), acetic acid is
largely undissociated. This permits diusion into the cell
cytoplasm, where it dissociates and decreases the intracellular pH. As a result, the proton gradient across the
membrane cannot be maintained and the transport of
various nutrients is impaired (Ko and Edwards, 1975;
Herrero et al., 1985). Hence, in the presence of acetate,
yeast fermentation of wood hydrolyzates is poor