Characterizing the Potential of the Non-Conventional Yeast Saccharomycodes ludwigii UTAD17 in Winemaking.

Vasconcelos Vasconcelos,Mendes-Ferreira Mendes-Ferreira,Esteves Esteves,Tavares Tavares,Barbosa Barbosa,Mendes-Faia Mendes-Faia,Mira Mira

doi:10.3390/microorganisms7110478

Abstract

Non-Saccharomyces yeasts have received increased attention by researchers and winemakers, due to their particular contributions to the characteristics of wine. In this group, Saccharomycodes ludwigii is one of the less studied species. In the present study, a native S. ludwigii strain, UTAD17 isolated from the Douro wine region was characterized for relevant oenological traits. The genome of UTAD17 was recently sequenced. Its potential use in winemaking was further evaluated by conducting grape-juice fermentations, either in single or in mixed-cultures, with Saccharomyces cerevisiae, following two inoculation strategies (simultaneous and sequential). In a pure culture, S. ludwigii UTAD17 was able to ferment all sugars in a reasonable time without impairing the wine quality, producing low levels of acetic acid and ethyl acetate. The overall effects of S. ludwigii UTAD17 in a mixed-culture fermentation were highly dependent on the inoculation strategy which dictated the dominance of each yeast strain. Wines whose fermentation was governed by S. ludwigii UTAD17 presented low levels of secondary aroma compounds and were chemically distinct from those fermented by S. cerevisiae. Based on these results, a future use of this non-Saccharomyces yeast either in monoculture fermentations or as a co-starter culture with S. cerevisiae for the production of wines with greater expression of the grape varietal character and with flavor diversity could be foreseen.

Highlights

Inoculation with active dry yeasts of Saccharomyces cerevisiae is a common practice in most wine-producing regions since the middle of the 20th century, to assure prompt and reliable fermentations and wines with a consistent and predictable quality
In order to assess the potential of S. ludwigii UTAD17 to be used in winemaking, a phenotypic profiling was performed for a number of oenological traits, as determined by the International Organisation of Vine and Wine (OIV) [68] (Figure S1)
Ethanol is the main metabolite produced during wine fermentation while SO2 and copper are applied by winemakers as antimicrobial agents to control spoilage in wineries and vineyards, respectively

Summary

Introduction

Inoculation with active dry yeasts of Saccharomyces cerevisiae is a common practice in most wine-producing regions since the middle of the 20th century, to assure prompt and reliable fermentations and wines with a consistent and predictable quality. Among the most studied non-Saccharomyces yeasts are the members of the genus Hanseniaspora (H. uvarum [24,25,26,27,28], H. guillermondii [24,25,26,29,30], and H. vineae [25,31,32,33,34]), Metschnikowia pulcherrima [21,33,35,36,37], Torulaspora delbrueckii [38,39,40,41,42,43], Kluyveromyces/Lachancea thermotolerans [44,45,46,47,48], and Starmerella bacillaris (formerly Candida stellata/Candida zemplinina) [27,49,50,51,52,53] In addition to their contribution to the enhancement and diversification of wine aroma, it was found that these yeasts might display other oenological relevant traits, such as increased glycerol, mannoprotein, and total acidity contents [16,46,52,54,55], contributing to color stability [56,57] and reducing volatile acidity or ethanol levels [21,33,36,38,58]. The growth and fermentation behavior, as well as the analytical profiles of the final wines, were evaluated, revealing that this strain could be useful for tailoring wines with enhanced varietal characters

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Results