Understanding the Role and Regulation of Cation Homeostasis during Citric Acid Stress in the Spoilage Yeast Saccharomyces Cerevisiae

Yeasts are able to spoil foods and beverages because they have evolved mechanisms that allow them to adapt and grow under the extreme environmental conditions, such as acid pH, that are often used to preserve foods and drinks. Citric acid (E330) and its salts are used extensively in the food and beverage industry to control pH and act as preservatives to prevent microbial growth, but little is known about how yeasts adapt and grow in the presence of the acid. Understanding of the precise mechanisms that regulate the adaptive responses of spoilage yeast to citric acid could lead to the enhancement of the preservative action of the compound, or to the development of new preservation routes that target the signalling mechanisms, that will be identified by this study, that switch on the adaptive response.
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In previous work, we have identified three genes that are known to control the intracellular levels of important cations, such as polyamines and metal ions, also play an essential role in permitting optimal adaptation of spoilage yeast to the inhibitory effect of citric acid. Thus, in this proposal we aim to: <OL> <LI> Determine why the regulation of cation levels is so important to citric acid adaptation; <LI>Identify the other proteins that make up the signalling pathways that regulate cation levels during citric acid stress; <LI>Determine whether or not the signalling pathways switch on the same, or different responses, and whether they do this by interacting together or via separate routes.