Modifications of Saccharomyces pastorianus cell wall polysaccharides with brewing process

•Yeast cell wall polysaccharides are modified over the brewing.•BSY mannoproteins are more branched and phosphorylated than the inoculum (IY).•Yeast cell wall 3D structure is preserved after mannoproteins extraction.•IY glucans are mainly (1→3)-linked and BSY are mainly (1→4)-linked.•IY and BSY (1→4)-linked Glc occur 2/3 in α- and 1/3 in β-anomeric configuration. The cell wall polysaccharides of brewers spent yeast Saccharomyces pastorianus (BSY) and the inoculum yeast (IY) were studied in order to understand the changes induced by the brewing process. The hot water and alkali extractions performed solubilized mainly mannoproteins, more branched for BSY than those of IY. Also, 31P solid state NMR showed that the BSY mannoproteins were 3 times more phosphorylated. By electron microscopy it was observed that the final residues of alkali sequential extraction until 4M KOH preserved the yeast three-dimensional structure. The final residues, composed mainly by glucans (92%), showed that the BSY, when compared with IY, contained higher amount of (1→4)-linked Glc (43% for BSY and 16% for IY) and lower (1→3)-linked Glc (17% for BSY and 42% for IY). The enzymatic treatment of final residue showed that both BSY and IY had (α1→4)-linked Glc and (β1→4)-linked Glc, in a 2:1 ratio, showing that S. pastorianus increases their cellulose-like linkages with the brewing process.