Weak organic acid treatment causes a trehalose accumulation in low-pH cultures of Saccharomyces, cerevisiae, not displayed by the more preservative-resistant Zygosaccharomyces bailii

Weak organic acid food preservatives exert pronounced culture pH-dependent effects on both the heat-shock response and the thermotolerance of Saccharo myces cerevisiae. In low-pH cultures, they inhibit this stress response and cause strong induction of respiratory-deficient petites amongst the surviv ors of lethal heat treatment. In higher pH cultures, 25 degrees C sorbic ac id treatment causes a strong induction of thermotolerance without inducing the heat-shock response. In this study we show that trehalose, a major stre ss protectant, accumulates rapidly in S. cerevisiae exposed to sorbate at l ow pH. In pH 3.5 cultures, a 25 degrees C sorbate treatment is as effective as a 39 degrees C heat shock in inducing trehalose. This weak-acid-induced trehalose accumulation is enhanced in the pfk1 S. cerevisiae mutant, indic ating that it arises through inhibition of glycolysis at the phosphofructok inase step. The more preservative-resistant food spoilage yeast Zygosacchar omyces bailii differs from S. cerevisiae in that: (1) its basal thermotoler ance is not strongly affected by culture pH: (2) it does not display trehal ose accumulation in response to 25 degrees C sorbate treatment at low pH; a nd (3) there is no induction of respiratory-deficient petites during lethal heating with sorbate. This probably reflects Z. bailii being both petite-n egative and better equipped for maintenance of homeostasis during weak-acid , pH or high-temperature stress. (C) 1999 Federation of European Microbiolo gical Societies. Published by Elsevier Science B.V. All rights reserved.