RESUMEN
Brewing practice uses the same yeast to inoculate the following fermentation (repitching). Saccharomyces pastorianus, used to produce Lager beer, is widely reused, not changing its fermentation performance. However, S. cerevisiae, used to produce Ale beer, is partial or not even reused, due to its poor performance. It is hypothesized that cells modulate their wall polysaccharides to increase the cell-wall strength. In this work industrial S. cerevisiae and S. pastorianus brewer's spent yeasts with different repitching numbers were studied. Glucans were the main component of S. cerevisiae whereas mannoproteins were abundant in S. pastorianus. The major changes were noticed on glucans of both species, ß1,3-glucans decrease more pronounced in S. cerevisiae. The increase of α1,4-Glc, related with osmotolerance, was higher in S. cerevisiae while ß1,4-Glc, related with cell-wall strength, had a small increase. In addition, these structural details showed different binding profiles to immune receptors, important to develop tailored bioactive applications.
