IMPACT OF MANNOPROTEIN N-GLYCOSYL PHOSPHORYLATION AND BRANCHING ON WINE POLYPHENOL INTERACTIONS WITH YEAST CELL WALLS
Yeast cell walls (CWs) may adsorb wine components with a significant impact on wine quality. When dealing with red wines, this adsorption is mainly related to physicochemical interactions between wine polyphenols and cell wall mannoproteins. However, mannoproteins are a heterogeneous family of complex peptidoglycans including long and highly branched N-linked oligosaccharides and short linear O-linked oligosaccharides, resulting in a huge structural diversity. Furthermore, the presence of mannosyl phosphate groups confers a net negative charge to the cell surface. The structural features in mannoproteins that promote their interactions with polyphenols and adsorption specificity are not clearly established yet. This work aimed to study the impact of mannosyl phosphorylation and mannan backbone branching on polyphenol adsorption by yeast cell walls.
Saccharomyces cerevisiae BY4742 Wild-type and mnn4 and mnn2 mutants (involved in N-glycosyl phosphorylation and mannan backbone branching, respectively) were obtained from EUROSCARF. Cell walls were purified and characterized in terms of total nitrogen, neutral sugar, and global charges. Their interactions with a red wine polyphenolic pool were studied in a wine-like solution by means of adsorption isotherms. Polyphenols were analyzed by means of UV-visible spectrophotometry and High-Per-formance Size-Exclusion Chromatography.
High molecular weight tannins and derived pigments were preferentially adsorbed whatever CW types, however, their affinity was significantly lower for mutants as compared to the wild-type. The mnn4 and mnn2 mutations induced changes in the mannose/protein ratio and a decrease of the CW net charge at wine pH. Both mutations induced a decrease in polyphenol affinity as well as a decrease in CW biosorption capacity, however, the latter was much more pronounced for the mnn4 mutant (N-glycosyl phosphorylation).
This work evidenced the key role of mannosyl phosphorylation on yeast CW functionality regarding wine polyphenol adsorption.
Issue: OENO Macrowine 2023
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Saccharomyces cerevisiae cell walls, Mannosyl phosphorylation, Mannan branching, Wine polyphenols adsorption