Vinification without Saccharomyces: Interacting Osmotolerant and "Spoilage" Yeast Communities in Fermenting and Ageing Botrytised High-Sugar Wines (Tokaj Essence).

Hajnalka Csoma,Kinga Czentye,Zoltán Kállai,Matthias Sipiczki,Zsuzsa Antunovics

doi:10.3390/microorganisms9010019

Hajnalka Csoma, Kinga Czentye + Show 3 more

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https://doi.org/10.3390/microorganisms9010019

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Journal: Microorganisms	Publication Date: Dec 23, 2020
Citations: 17	License type: CC BY 4.0

Affiliation: University of Debrecen

Abstract

The conversion of grape juice to wine starts with complex yeast communities consisting of strains that have colonised the harvested grape and/or reside in the winery environment. As the conditions in the fermenting juice gradually become inhibitory for most species, they are rapidly overgrown by the more adaptable Saccharomyces strains, which then complete the fermentation. However, there are environmental factors that even Saccharomyces cannot cope with. We show that when the sugar content is extremely high, osmotolerant yeasts, usually considered as “spoilage yeasts“, ferment the must. The examination of the yeast biota of 22 botrytised Tokaj Essence wines of sugar concentrations ranging from 365 to 752 g∙L−1 identified the osmotolerant Zygosaccharomyces rouxii, Candida (Starmerella) lactis-condensi and Candida zemplinina (Starmerella bacillaris) as the dominating species. Ten additional species, mostly known as osmotolerant spoilage yeasts or biofilm-producing yeasts, were detected as minor components of the populations. The high phenotypical and molecular (karyotype, mtDNA restriction fragment length polymorphism (RFLP) and microsatellite-primed PCR (MSP-PCR)) diversity of the conspecific strains indicated that diverse clones of the species coexisted in the wines. Genetic segregation of certain clones and interactions (antagonism and crossfeeding) of the species also appeared to shape the fermenting yeast biota.

Highlights

The conversion of grape must to wine is the result of the joint activities of multiple yeast species
We showed that osmotolerant yeasts that are considered unwanted spoiling organisms in wine-making can ferment high-sugar botrytised grape must without the contribution of Saccharomyces
Six of the eight wines produced in the 2019 vintage had high CFU counts and showed other signs of active fermentation

Summary

Introduction

The conversion of grape must to wine is the result of the joint activities of multiple yeast species. The spontaneous fermentation process starts with a mixed community of yeast species that are determined primarily by the yeast populations colonising the harvested grape and the winery environment (e.g., [1,2,3]). The composition of the community rapidly changes in the fermenting must because most non-Saccharomyces yeasts die and strains of the species Saccharomyces cerevisiae, Saccharomyces uvarum and genomic chimeras of various Saccharomyces species take the lead and drive the fermentation to completion. A few non-Saccharomyces strains can persist until the end of fermentation (e.g., [5,6,7,8,9,10]).

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