Quantifying the Effects of Ethanol and Temperature on the Fitness Advantage of Predominant Saccharomyces cerevisiae Strains Occurring in Spontaneous Wine Fermentations

Abstract

Different Saccharomyces cerevisiae strains are simultaneously or in succession involved in spontaneous wine fermentations. In general, few strains occur at percentages higher than 50% of the total yeast isolates (predominant strains), while a variable number of other strains are present at percentages much lower (secondary strains). Since S. cerevisiae strains participating in alcoholic fermentations may differently affect the chemical and sensory qualities of resulting wines, it is of great importance to assess whether the predominant strains possess a “dominant character.” Therefore, the aim of this study was to investigate whether the predominance of some S. cerevisiae strains results from a better adaptation capability (fitness advantage) to the main stress factors of oenological interest: ethanol and temperature. Predominant and secondary S. cerevisiae strains from different wineries were used to evaluate the individual effect of increasing ethanol concentrations (0-3-5 and 7% v/v) as well as the combined effects of different ethanol concentrations (0-3-5 and 7% v/v) at different temperature (25–30 and 35°C) on yeast growth. For all the assays, the lag phase period, the maximum specific growth rate (μmax) and the maximum cell densities were estimated. In addition, the fitness advantage between the predominant and secondary strains was calculated. The findings pointed out that all the predominant strains showed significantly higher μmax and/or lower lag phase values at all tested conditions. Hence, S. cerevisiae strains that occur at higher percentages in spontaneous alcoholic fermentations are more competitive, possibly because of their higher capability to fit the progressively changing environmental conditions in terms of ethanol concentrations and temperature.

The Biodiversity of Saccharomyces cerevisiae in Spontaneous Wine Fermentation: The Occurrence and Persistence of Winery-Strains

“…However, considering the frequency of different S. cerevisiae strains within each winery in the various vintages, showed one or two predominant strains occurring at high frequencies (>25%), in association with a variable number of secondary strains at low frequencies (<10%), (Table 2). In addition, some predominant strains were shared by different grape varieties fermented in various tanks, pointing out that no correlation occurred between specific yeast strains and the grape variety, as reported by Ganucci et al [8]. The occurrence of a few predominant S. cerevisiae strains at percentages >25% carrying out the spontaneous wine fermentations, is consistent with many other studies accomplished in different oenological regions [6][7][8][11][12][13]19].…”

“…The results shown in Table 2 revealed that, independently of the winery, indigenous S. cerevisiae populations showed a high amount of polymorphism, confirming the general trend reported in the literature on spontaneous wine fermentations [2][3][4][5][6][7][8][11][12][13][14][15][16][17][18][19]22,24]. However, considering the frequency of different S. cerevisiae strains within each winery in the various vintages, showed one or two predominant strains occurring at high frequencies (>25%), in association with a variable number of secondary strains at low frequencies (<10%), (Table 2).…”

“…Several studies, by means of various molecular methods, have largely demonstrated that native S. cerevisiae populations display a significant genetic diversity and that different strains are simultaneously or in succession involved during the alcoholic fermentation [3][4][5][6][7]. Despite this high polymorphism, generally, a few indigenous S. cerevisiae strains occurring at higher percentages (more than 30-50% of the total yeast isolates) are able to predominate the fermentative process, while a variable number of strains are present at lower percentages [1,[7][8][9][10][11][12]. The presence of these predominant S. cerevisiae strains has been related to their higher adaptation capability (fitness advantage) to some stress factors of oenological interest, such as increasing ethanol concentrations and temperature changes, along with cell-to-cell contact mechanisms occurring during the alcoholic fermentation [8][9][10].…”

Selection of Saccharomyces cerevisiae Starter Strain for Merwah Wine

“…Some winemakers argue that authentic expression of terroir and vintage can only be achieved through fermentation with indigenous yeasts. Other winemakers prefer the greater security and controlled variability of specialized strains [3].…”

The CGI121 gene from Saccharomyces cerevisiae demonstrates genetic linkage to increased lag time under enological conditions

“…However, low temperatures also dramatically increase the time taken until fermentation completion and the risk of ferments becoming stuck or sluggish, which is potentially costly in terms of reduced winery space, product loss and decreased pro ts [4][5][6][7][8]. Low temperatures encountered during fermentation are particularly stressful to yeast and cause changes in cell membrane uidity, nutrient uptake and utilization, production of protective compounds, and a decrease in enzymatic reactions [6,[9][10][11]. A greater understanding of the genetics behind the ability of the wine yeast, Saccharomyces cerevisiae, to acclimate to low temperatures and perform fermentation more e ciently in general, is therefore useful for the wine industry.…”