Yeast cell wall-derived proteins: Identification and characterization as food emulsifiers

Emulsification activity has been identified in the cell wall mannoproteins of Saccharomyces cerevisiae —which is widely utilized in food products—and their applications have been explored. However, apart from Gas proteins, no other emulsifying cell wall proteins have been identified. A comprehensive understanding of the cell wall proteins involved in emulsification is crucial for advancing their applications. Herein, emulsifying proteins easily released from the cell wall, unlike Gas proteins that are covalently attached, were purified and characterized. Consequently, fructose 1,6-bisphosphate aldolase 1 (Fba1), Enolase (Eno) 1, and Eno2 showed emulsifying activity, and Fba1 had the highest activity. These are glycolytic proteins localized in the cytoplasm and cell wall. Because Triose-phosphate dehydrogenase (glyceraldehyde-3-phosphate dehydrogenase) 2 (Tdh2)—another glycolytic protein—is also localized in the cell wall, its emulsifying ability was investigated. Results indicated that Tdh2 also had strong activity and was comparable to the activity of casein, an emulsifier. Moreover, Tdh2 displayed higher emulsifying activity with 14 and 16 carbon hydrocarbons and stabilized emulsions in soybean oil. Tdh2—with a smaller molecular weight and nearly absent sugar chains compared to Gas proteins—holds promise for investigating the relationship between protein structure and emulsification. This study identified new emulsifying proteins localized to the cell wall through mechanisms other than covalent bonding. In addition, these proteins have potential applications as yeast-derived emulsifiers. • Analyzing emulsifying proteins that were easily released from yeast cell wall. • Identifying four glycolytic proteins localized in the cell wall via non-covalent bonds. • Fba1 & Tdh2 have higher emulsifying activity than Eno1 & 2. • Tdh2 brings higher emulsion stability to soybean oil than casein, an emulsifier. • These proteins have potential applications as yeast-derived emulsifiers.