Unraveling the Enzymatic Basis of Wine "Flavorome": A Phylo-Functional Study of Wine Related Yeast Species

Abstract

Non-Saccharomyces yeasts are a heterogeneous microbial group involved in the early stages of wine fermentation. The high enzymatic potential of these yeasts makes them a useful tool for increasing the final organoleptic characteristics of wines in spite of their low fermentative power. Their physiology and contribution to wine quality are still poorly understood, with most current knowledge being acquired empirically and in most cases based in single species and strains. This work analyzed the metabolic potential of 770 yeast isolates from different enological origins and representing 15 different species, by studying their production of enzymes of enological interest and linking phylogenetic and enzymatic data. The isolates were screened for glycosidase enzymes related to terpene aroma release, the β-lyase activity responsible for the release of volatile thiols, and sulfite reductase. Apart from these aroma-related activities, protease, polygalacturonase and cellulase activities were also studied in the entire yeast collection, being related to the improvement of different technological and sensorial features of wines. In this context, and in terms of abundance, two different groups were established, with α-L-arabinofuranosidase, polygalacturonase and cellulase being the less abundant activities. By contrast, β-glucosidase and protease activities were widespread in the yeast collection studied. A classical phylogenetic study involving the partial sequencing of 26S rDNA was conducted in conjunction with the enzymatic profiles of the 770 yeast isolates for further typing, complementing the phylogenetic relationships established by using 26S rDNA. This has rendered it possible to foresee the contribution different yeast species make to wine quality and their potential applicability as pure inocula, establishing species-specific behavior. These consistent results allowed us to design future targeted studies on the impact different non-Saccharomyces yeast species have on wine quality, understanding intra and interspecific enzymatic odds and, therefore, aiming to predict the most suitable application for the current non-Saccharomyces strains, as well as the potential future applications of new strains. This work therefore contributes to a better understanding of the concept of wine microbiome and its potential consequences for wine quality, as well as to the knowledge of non-Saccharomyces yeasts for their use in the wine industry.

Keywords: enological enzymes; microbial terroir; non-Saccharomyces; phylo-functional study; targeted yeast selection.

Figure 1

Population distribution across the 770 yeast isolates.

Figure 2

Total and vintage-specific population distribution from the four sampled vineyards. (A) Population distribution of EM vineyard. (B) Population distribution of PDC vineyard. (C) Population distribution of O vineyard. (D) Population distribution of G vineyard.

Figure 3

Abundance and distribution of enzymatic activities among the total yeast collection, individually considering the 15 yeast species identified. The eight enzymatic activities evaluated were: (A) β-glucosidase; (B) β-D-xylosidase; (C) α-L-arabinofuranosidase; (D) β-lyase; (E) Protease; (F) Polygalacturonase; (G) Cellulase; (H) Hydrogen sulfide production. Enzymatic activity was determined on a scale from 1 (no activity) to 5 (highest activity) corresponding to a progressive color code from green to red.

Figure 4

Intraspecific distribution of isolates from the four origins and their corresponding vintages sampled. Tridimensional plots correspond to the PCA analysis of specific populations considering their enzymatic activities, and group separation was calculated with the Jackknife method. Color legends: red (EM 2013), pink (EM 2014), blue (PDC 2013), cyan (PDC 2014), dark green (O 2013), pale green (O 2014), and yellow (G 2012). Tridimensional visualization was captured in order to optimize group distinction.