Fungal resident flora of a new winery: colonization, dynamics and potential persistence capacities

Abstract

Through the years, extensive studies have been conducted on fungal biodiversity during the winemaking process: from the vineyard until aging. More recently, and as previously described for Saccharomyces cerevisiae, the persistence of winery resident flora (non-Saccharomyces yeasts) over time and its contribution to the alcoholic fermentation have been demonstrated. Also, winery surfaces were described as a true ecological niche and a transitional habitat for this resident flora. 

To our knowledge, no study has been done on the evolution and persistence of indigenous yeast flora in a new winery nor on the capacities of this indigenous flora to persist in the winery environment. Thus, the first objective of this work is to study the diversity and to follow the evolution of fungal communities in a new established winery operating only with indigenous yeast flora and for a period of 3 vintages (2016, 2017 and 2018). For this purpose, samples were collected from three different winery surfaces (soil, walls and equipment), at separate time points (before grape harvest, during the fermenting phase and 3 months after the fermentations) and were analyzed using the Mi-Seq sequencing. In a second objective, genetic diversity, persistence in winery environments and the implantation in must /or wine of indigenous S. cerevisiae isolates were monitored for all the collected samples using microsatellites PCRs. In addition, the killer character and biofilm formation of different isolated strains were investigated to determine potential capacities to persist in winery environments. 

The results obtained showed a high fungal diversity (yeasts, fungi and mold) on the 3 winery environments even before the first grape harvest (2016). As for yeasts, previously described genera (Candida, Metschinikowia, Rhodotorula, Saccharomyces, Wickerhamomyces, …) have been identified on winery surfaces but also yeast genera (Buckleyzyma, Curvibasidium, Leucosporidium, …) that have not been before described in the winemaking process. Then, the observed fungal diversity showed evolution over time and dependently according to each of the studied environment. Additionally, some fungal equilibria appears to take place between genera such as Aureobasidium, Candida and Wickerhamomyces. 

Concerning indigenous S. cerevisiae strains, our results demonstrated the potential implantation and persistence of some strains present in the winery environment during 2017 and 2018 vintages and during the alcoholic fermentations. Thus, selected strains of indigenous S. cerevisiae seem to have different physiological characteristics that could explain their potential persistence in winery environments.