In the current investigation, we monitored yeast viability using

primuline following two methods of yeast rehydration: quick and slow rehydration. The first approach rehydrated cells for 10 min and this is known to fix the yeast plasma membrane in a state similar to that following dehydration– rehydration stress. Previous experiments (Beker & Rapoport, 1987) showed that it was not possible to improve the viability of such cells by prolonging their incubation in water. The second approach facilitated slow rehydration of cells in water vapour for 1 h and this led to full reparation of reversible damage to Ku-0059436 price the yeast plasma membrane, as shown previously (Rapoport et al., 2009), by detecting changes in the phase transition temperatures of yeast membrane lipids. Figure 2 shows that magnesium bioavailability did not influence the stability of yeast cells in the exponential phase of growth. It is noteworthy that very low viabilities of S. cerevisiae taken for dehydration–rehydration from the exponential growth phase are normal for this growth phase (see Beker & Rapoport, 1987). In contrast, cells taken from the stationary phase before dehydration–rehydration procedures were of higher viabilities (Fig. 2). Stationary-phase cells also exhibited maximum

resistance to dehydration–rehydration when PI3K inhibitor grown in media with 0.15 g L−1 magnesium. It is apparent that at different yeast culture growth phases, magnesium exhibited different effects on cells. Thus, exponential growth-phase supplementations with certain levels of magnesium ions promoted a higher biomass yield. In the stationary growth phase, magnesium conferred on cells a higher resistance to dehydration–rehydration treatments. It is likely that yeast cells require strictly

defined levels of Mg2+ ions for maximizing growth and stress resistance. The growth-stimulatory effects of magnesium during the exponential phase may be linked to the activation of key metabolic enzymes, such as transphosphorylases (Walker, 1999). Additionally, magnesium may exert a protective influence on dehydrated stationary growth-phase cells by acting as a charge stabilizer of cell membranes. Thus, compromising magnesium bioavailability can lead to unfavourable CYTH4 changes in yeast cell physiology, notably their ability to withstand dehydration–rehydration. The influence of calcium on yeast cell resistance to dehydration–rehydration treatments was studied using unsupplemented molasses nutrient medium (which contained optimum concentrations of Mg2+– 0.15 g L−1 of Mg2+), and the results are shown in Fig. 2. It is evident that addition of Ca2+ ions had little effect on the stability of yeast cells from the exponential growth phase with regard to dehydration–rehydration treatments. It can also be seen that the addition to the medium of 2 g L−1 of Ca2+ was accompanied by a small increase (8–10%) in the viability of dehydrated cultures from the stationary growth phase.