Author(s):
Sousa, Maria João 
; Estevinho, Leticia M. ; Côrte-Real, Manuela ; Leão, Cecília
Date: 1996
Persistent ID: http://hdl.handle.net/10198/4395
Origin: Biblioteca Digital do IPB
Subject(s): Zygosaccharomyces bailii
Description
Cells of Zygosaccharomyces bailii ISA 1307 grown in a medium with acetic acid, ethanol, or glycerol as the sole
carbon and energy source transported acetic acid by a saturable transport system. This system accepted
propionic and formic acids but not lactic, sorbic, and benzoic acids. When the carbon source was glucose or
fructose, the cells displayed activity of a mediated transport system specific for acetic acid, apparently not
being able to recognize other monocarboxylic acids. In both types of cells, ethanol inhibited the transport of
labelled acetic acid. The inhibition was noncompetitive, and the dependence of the maximum transport rate on
the ethanol concentration was found to be exponential. These results reinforced the belief that, under the
referenced growth conditions, the acid entered the cells mainly through a transporter protein. The simple
diffusion of the undissociated acid appeared to contribute, with a relatively low weight, to the overall acid
uptake. It was concluded that in Z. bailii, ethanol plays a protective role against the possible negative effects
of acetic acid by inhibiting its transport and accumulation. Thus, the intracellular concentration of the acid
could be maintained at levels lower than those expected if the acid entered the cells only by simple diffusion.
