Brewer's spent yeast (BSY) microcapsules have a complex network of cell-wall polysaccharides that are induced by brewing when compared to the baker's yeast (Saccharomyces cerevisiae) microcapsules. These are rich in (β1→3)-glucans and covalently linked to (α1→4)- and (β1→4)-glucans in addition to residual mannoproteins. S. cerevisiae is often used as a drug delivery system due to its immunostimulatory potential conferred by the presence of (β1→3)-glucans. Similarly, BSY microcapsules could also be used in the encapsulation of compounds or drug delivery systems with the advantage of resisting digestion conferred by (β1→4)-glucans and promoting a broader immunomodulatory response. This work aims to study the feasibility of BSY microcapsules that are the result of alkali and subcritical water extraction processes, as oral carriers for food and biomedical applications by (1) evaluating the resistance of BSY microcapsules to in vitro digestion (IVD), (2) their recognition by the human Dectin-1 immune receptor after IVD, and (3) the recognition of IVD-solubilized material by different mammalian immune receptors. IVD digested 44-63% of the material, depending on the extraction process. The non-digested material, despite some visible agglutination and deformation of the microcapsules, preserved their spherical shape and was enriched in (β1→3)-glucans. These microcapsules were all recognized by the human Dectin-1 immune receptor. The digested material was differentially recognized by a variety of lectins of the immune system related to (β1→3)-glucans, glycogen, and mannans. These results show the potential of BSY microcapsules to be used as oral carriers for food and biomedical applications.
Keywords: DC-SIGN; Dectin-1; Dectin-2; carbohydrate microarrays; delivery systems; glucans; in vitro digestion; innate immune system; mannoproteins.