Valorisation of brewer’s spent yeast: Impact of pre-treatment and autolysis on mannoproteins, β-glucans, and bioactive compounds for food packaging applications.

The brewing industry generates large quantities of by-products, including brewer’s spent yeast (BSY), which represents a particularly valuable matrix due to its high content of bioactive compounds such as β-glucans, mannoproteins, and fatty acids. However, the valorisation of BSY requires strategies that can promote the release of these components, which are often trapped within the cell wall. In this study, ten samples, one control and 9 samples derived from different BSY pre-treatment and autolysis processes, were analysed. The samples were fractionated into three components: autolysate (LIS), protein hydrolysate (PH), and yeast cell debris (YCD). The aim was to evaluate the impact of these treatments on the release of bioactive compounds. Parameters such as pH, dry matter content, β-glucan and mannoprotein levels, lipid profile, antioxidant activity, and antimicrobial activity were analysed. The results showed that autolysis treatments (24 and 72 hours) significantly promoted the release of β-glucans and mannoproteins, with higher concentrations of these compounds found in the LIS fractions. Lipid analysis identified palmitic acid (C16:0) as the most abundant fatty acid, followed by oleic acid (C18:1), with a notable presence of medium-chain fatty acids (C8:0–C12:0) in LIS and YCD. All samples exhibited measurable antioxidant activity, although no clear trend was observed among the different fractions, likely due to treatment variability. Antimicrobial assays revealed selective inhibitory effects against Listeria monocytogenes, particularly in YCD fractions at both 5% and 10% concentrations, suggesting a correlation with the presence of short-chain fatty acids, as well as other bioactive compounds such as polyphenols and glutathione. These findings highlight the potential of BSY as a source of bioactive compounds for food applications, including natural antimicrobials and antioxidants, and for the development of sustainable packaging materials in line with circular economy principles.