Application of yeast spores as β-glucan particles

Abstract

β-Glucan exhibits various beneficial biological activities including immunostimulation. This polysaccharide is present in the cell wall of microorganisms including the yeast Saccharomyces cerevisiae. Although vegetative yeast cells are used as dietary supplements, β-glucan in the vegetative cell wall is covered with mannan. During nutrient starvation, yeast cells differentiate into dormant cell spores. β-Glucan is also present in the spore wall, but spores have been poorly studied as application tools. The spore wall consists of four layers and β-glucan forms the third layer from the outside. However, unlike vegetative cells, the β-glucan layer can be exposed to the cell surface in spores by genetic manipulation. For example, chs3Δ mutant spores exhibit such a spore wall configuration. Dectin-1 is the primary receptor for β-glucan in mammals and, its activation induces phagocytosis and proinflammatory cytokine secretions. We found that chs3Δ spores are phagocytosed in mammalian cells in a manner dependent on dectin-1 and induce higher levels of TNF-α and IL-6 than vegetative cells. Our results demonstrate that chs3Δ spores are β-glucan particles with immunostimulatory activities. Thus, they would be attractive materials for application in the food industry.