Effect of a Multistarter Yeast Inoculum on Ethanol Reduction and Population Dynamics in Wine Fermentation

Abstract

Microbiological strategies are currently being considered as methods for reducing the ethanol content of wine. Fermentations started with a multistarter of three non-Saccharomyces yeasts (Metschnikowia pulcherrima (Mp), Torulaspora delbrueckii (Td) and Zygosaccharomyces bailii (Zb)) at different inoculum concentrations. S. cerevisiae (Sc) was inoculated into fermentations at 0 h (coinoculation), 48 h or 72 h (sequential fermentations). The microbial populations were analyzed by a culture-dependent approach (Wallerstein Laboratory Nutrient (WLN) culture medium) and a culture-independent method (PMA-qPCR). The results showed that among these three non-Saccharomyces yeasts, Td became the dominant non-Saccharomyces yeast in all fermentations, and Mp was the minority yeast. Sc was able to grow in all fermentations where it was involved, being the dominant yeast at the end of fermentation. We obtained a significant ethanol reduction of 0.48 to 0.77% (v/v) in sequential fermentations, with increased concentrations of lactic and acetic acids. The highest reduction was achieved when the inoculum concentration of non-Saccharomyces yeast was 10 times higher (107 cells/mL) than that of S. cerevisiae. However, this reduction was lower than that obtained when these strains were used as single non-Saccharomyces species in the starter, indicating that interactions between them affected their performance. Therefore, more combinations of yeast species should be tested to achieve greater ethanol reductions.

Adaptation of Ancient Techniques to Recreate ‘Wines’ and ‘Beverages’ Using Withered Grapes of Muscat of Alexandria

“…This higher ethanol yield may be explained by the likely higher lipid concentration in the lees juice [33]. Concerning wine yields, 100 L of passito-style wine was obtained, resulting in 0.37 L/kg of dehydrated grapes, comparable to the yields reported by Rolle et al [31].…”

“…Moreover, grape dehydration induced an increase in acetic acid of up to 0.25 g/L in a random sample of single berries. Probably, acetic acid increased in a mode similar to gluconic acid in gradually more dehydrated berries [31], thus justifying further research.…”

Evaluation of Autochthonous Non-Saccharomyces Yeasts by Sequential Fermentation for Wine Differentiation in Galicia (NW Spain)

“…bacillaris Sb474, and K. dobzhanskii Kd231 were still the dominant yeasts at high proportions after the addition of S. cerevisiae (93%, 76%, and 95%, respectively), although their proportions decreased at the end. The prevalence of T. delbrueckii in sequential fermentations at the tumultuous and later stages was recently reported in multi-starter fermentations [38], and it had already been found at pilot-scale fermentations [39,40], especially when a killer T. delbrueckii strain was used [41,42], or in the production of wines with reduced sulfites [43]. However, other authors observed a reduction in T. delbrueckii and other non-Saccharomyces from two to four days after the second inoculation [44] in laboratory fermentations.…”

“…Little information is available about the enological traits of P. kudriavzevii, but the data confirmed that, in mixed fermentations, its population rapidly decreased due to the fact of its weak ethanol tolerance [50]. Regarding Zygosaccharomyces, Zhu et al [51] reported a fast decrease in viability in sequential fermentations after 8 days; however, in multi-starter fermentations, the maximum growth was reached in the late fermentation stage, and it was maintained rather stably until the end of fermentation [38].…”

Survey of Inoculated Commercial Saccharomyces cerevisiae in Winery-Based Trials

“…On the other hand, recent studies on the dominance of different inoculated strains have mostly been carried out on mixed fermentations with non-Saccharomyces yeasts and S. cerevisiae with the aim of understanding the behavior and interactions of strains throughout the fermentation process [11][12][13][14]. Fewer studies have focused on the population dynamics of different inoculated strains of S. cerevisiae, as reported by Gustafsson et al [15].…”