The Effect of Ethanol on the Plasma Membrane Permeability of Spoilage Yeasts
Célia Quintas1,2*, Emília Lima-Costa1 and Maria C. Loureiro-Dias1,3
1Unidade de Ciências e Tecnologias Agrárias, Campus de Gambelas
2Escola Superior de Tecnologia, Campus da Penha, Universidade do Algarve, 8000 Faro, Portugal
3Departamento de Botânica e Engenharia Biológica Instituto Superior de Agronomia, 1349-017 Lisboa, Portugal
Article history:
Received November 10, 1999
Accepted January 21, 2000
Key words:
food spoilage yeasts, proton influx, plasma membrane permeability
Summary:
The effect of ethanol on the passive proton influx and on leakage of compounds absorbing at 260 nm, as representatives of intracellular content, was studied on food spoilage yeasts such as Saccharomyces cerevisiae, Zygosaccharomyces bailii, Pichia sp. and Debaryomyces hansenii. For volume fraction below 10 %, the effect of ethanol on the proton influx was in general weak, but above a certain treshold of ethanol high values were observed. In Z. bailii ethanol had no effect up to 20 % (volume fraction). Previous growth of the cells in the presence of benzoic acid or ethanol did not affect the influx of protons in the presence of ethanol. Leakage of compounds absorbing at 260 nm was not observed at 25 °C and occurred at 30 °C only after a rather long incubation in high concentrations of ethanol, which induced cell death. This suggests that in the yeasts this process does not control the leakage of compounds in the presence of ethanol.
