Redox Interactions betweenSaccharomyces cerevisiaeandSaccharomyces uvarumin Mixed Culture under Enological Conditions

Abstract

Wine yeast starters that contain a mixture of different industrial yeasts with various properties may soon be introduced to the market. The mechanisms underlying the interactions between the different strains in the starter during alcoholic fermentation have never been investigated. We identified and investigated some of these interactions in a mixed culture containing two yeast strains grown under enological conditions. The inoculum contained the same amount (each) of a strain of Saccharomyces cerevisiae and a natural hybrid strain of S. cerevisiae and Saccharomyces uvarum. We identified interactions that affected biomass, by-product formation, and fermentation kinetics, and compared the redox ratios of monocultures of each strain with that of the mixed culture. The redox status of the mixed culture differed from that of the two monocultures, showing that the interactions between the yeast strains involved the diffusion of metabolite(s) within the mixed culture. Since acetaldehyde is a potential effector of fermentation, we investigated the kinetics of acetaldehyde production by the different cultures. The S. cerevisiae-S. uvarum hybrid strain produced large amounts of acetaldehyde for which the S. cerevisiae strain acted as a receiving strain in the mixed culture. Since yeast response to acetaldehyde involves the same mechanisms that participate in the response to other forms of stress, the acetaldehyde exchange between the two strains could play an important role in inhibiting some yeast strains and allowing the growth of others. Such interactions could be of particular importance in understanding the ecology of the colonization of complex fermentation media by S. cerevisiae.Traditionally, indigenous yeast populations were used in the alcoholic fermentation step of wine making. Due to their strong resistance to ethanol, Saccharomyces cerevisiae strains usually predominate until the later stages of fermentation. In the last 20 years, however, winemakers have begun to use pure S. cerevisiae strains in the form of active dry yeast (ADY) starters. This process allows better control of fermentation and reduces the risk of organoleptic effects resulting from the growth and metabolism of other indigenous yeasts. In some cases, wine produced with pure yeast monocultures lacks the complexity of taste and other desirable characters that originate from the indigenous yeasts (16,35,51). The incorporation of several wine yeast strains with different technological capabilities into the same ADY starter may help overcome these shortcomings.Metabolic interactions in mixed strain bacterial cultures and between fungi and bacteria have been identified (12,26,30,41,43,47), but studies of such interactions in mixed yeast strain cultures are not common. In one study of mixed strain cultures for enological purposes, an exchange of metabolites between strains was observed (20). A mathematical model also is available to simulate growth in a mixed culture of strains of S. cerevisiae with and without the KII killer toxin (28, 31), but ...

Quantitative 1H-NMR-Metabolomics Reveals Extensive Metabolic Reprogramming and the Effect of the Aquaglyceroporin FPS1 in Ethanol-Stressed Yeast Cells

“…Another possible cause for such an apparent decreased ability to regenerate NAD + may be the inhibitory effect of ethanol at the level of the mitochondrial respiratory chain, whose function depends deeply on membrane integrity. Strongly linked with the intracellular redox status is the type and amount of by-products formed during yeast metabolism [44], [45], [50], [51], [52], [53]. Indeed, the exo-metabolome analysis carried out herein showed a higher accumulation in the broth medium of acetate, pyruvate, acetoin and acetaldehyde when ethanol is exogenously added, in a dose dependent way.…”

Wine microbiome: A dynamic world of microbial interactions

“…Cheraiti et al (2005) showed that the maximum population of a mixed culture of S. cerevisiae and a S. cerevisiae x S.…”

Online monitoring of Mezcal fermentation based on redox potential measurements

“…During storing and aging of wine, oxidation and reduction processes affect the character and taste of wine to a considerable extent [11,12]. We surmise that the same features could occur in the case of Mezcal making.…”

“…Previously, various attempts of relating the redox potential to fermentation processes have been made taking into account that redox potential assesses the growth ability of microorganisms, as well as the physiological activity in a given environment [8][9][10][11]. Particularly, the practical significance of redox potential and oxygen content at various stages of winemaking was examined in Ref.…”