Abstract
Yeast cell walls (CWs) may adsorb red wine polyphenols with a significant impact on wine quality. This adsorption is mainly attributed to physicochemical interactions with mannoproteins. However, the mannoprotein structural features that promote polyphenol adsorption are not clearly established yet. The impact of mannosylphosphorylation and mannan backbone branching on polyphenol adsorption by yeast was studied through adsorption isotherms with Saccharomyces cerevisiae BY4742 wild-type and mnn4 and mnn2 mutants (EUROSCARF). Polymeric and oligomeric tannins and derived pigments were preferentially adsorbed by the yeasts and their corresponding CWs. Mannoprotein N-glycosyl phosphorylation appeared as the key groupments involved in polyphenol adsorption by CWs. When dealing with whole yeasts, behaviors were different, due to the coupled phenomena of polyphenol adsorption at cell wall level and their diffusion inside the yeast cytoplasm. The key role of phosphorylation observed in this work is of interest in the modulation of wine color and astringency by yeasts.