Unusual Non-Saccharomyces Yeasts Isolated from Unripened Grapes without Antifungal Treatments

José Juan Mateo,Patricia Garcerà,Sergi Maicas

doi:10.3390/fermentation6020041

José Juan Mateo, Patricia Garcerà + Show 1 more

Open Access

https://doi.org/10.3390/fermentation6020041

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Journal: Fermentation	Publication Date: Apr 21, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: University of Valencia

Abstract

There a lot of studies including the use of non-Saccharomyces yeasts in the process of wine fermentation. The attention is focused on the first steps of fermentation. However, the processes and changes that the non-Saccharomyces yeast populations may have suffered during the different stages of grape berry ripening, caused by several environmental factors, including antifungal treatments, have not been considered in depth. In our study, we have monitored the population dynamics of non-Saccharomyces yeasts during the ripening process, both with biochemical identification systems (API 20C AUX and API ID 32C), molecular techniques (RFLP-PCR) and enzymatic analyses. Some unusual non-Saccharomyces yeasts have been identified (Metschnikowia pulcherrima, Aureobasidium pullulans, Cryptococcus sp. and Rhodotorula mucilaginosa). These yeasts could be affected by antifungal treatments used in wineries, and this fact could explain the novelty involved in their isolation and identification. These yeasts can be a novel source for novel biotechnological uses to be explored in future work.

Highlights

Grape berries microbiota refers to all species of filamentous fungus, yeast and bacteria that have been found in grape berries, in vineyard soil or in wine
Yeasts that are found in grape berries can be classified into two groups: (i) Saccharomyces, those which are responsible for sugar fermentation in grape berries, and (ii) non-Saccharomyces or wild yeast
In samples from untreated vineyards, yeast population increased during the ripening process, being at its maximum in the final stage

Summary

Introduction

Grape berries microbiota refers to all species of filamentous fungus, yeast and bacteria that have been found in grape berries, in vineyard soil or in wine. Regarding yeasts, these microorganisms belong to Ascomycetes, Basidiomycetes and Deuteromycetes classes [1]. Non-Saccharomyces yeasts can be detected before the fermentation process, i.e., during ripening and harvest processes The development of these yeasts has been observed on the surface of grape berries and their must and in the environment where the wine production takes place and in the wine cellar equipment. These places can be considered specialized niches for non-Saccharomyces yeasts [5,6]

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