During alcoholic fermentations, some non-Saccharomyces yeasts are often displaced by Saccharomyces cerevisiae. It remains unclear whether this displacement is mediated by metabolites produced by S. cerevisiae or depends on cell–cell contact. This study evaluated the effects of extracellular metabolites produced by S. cerevisiae on the growth and fermentative performance of Kluyveromyces marxianus isolated from mezcal fermentations. The development of both yeasts was evaluated in monocultures and in co-cultures with physical contact. Indirect interaction was also tested by exchanging cell-free fermented media. The growth and fermentative response of K. marxianus in cell-free S. cerevisiae-fermented medium showed modulation that depended on the growth phase during which the exchange was performed. The exchange performed at 6 h (exponential phase) limited the maximum growth of K. marxianus and resulted in lower fermentative performance. When the exchange was done during the stationary phase (17.5 h), K. marxianus exhibited a longer stationary phase and better fermentative performance. Finally, when the exchange was performed at 24 h (the beginning of the death phase), the effects on survival and fermentative performance were less pronounced. Furthermore, co-culture with cell–cell contact showed that direct competition and/or mechanisms dependent on physical contact intensify the displacement of K. marxianus. The results show that direct cell–cell contact promotes greater inhibition of K. marxianus by S. cerevisiae, which is relevant for the design of mixed fermentations aimed at achieving a greater contribution of non-Saccharomyces yeasts to the organoleptic characteristics of alcoholic beverages.
Gallardo-Rivera et al. (Thu,) studied this question.