Microbial fermentation and high-pressure homogenization as integrated strategies for the valorization of brewer’s spent grains into functional food ingredients

Every year, around a third of the food intended for human con- sumption is lost, including significant quantities of cereals, fruit and vegetables. The PROACTIVE project (PRIN 2020, Prot. 2020CNRB84) focuses on the valorisation of food by-products to obtain bioactive peptides to be used in health-oriented food applications. Among the approaches investigated, microbial fermentation and high pressure homogenisation (HPH) could potentially improve the increase of bi- oactive peptides in food by-products such as brewer's spent grains (BSG). In our study, after substrate optimisation, BSG was fermented with selected yeast and lactic acid bacteria with or without prior HPH treatment on the strains (500–1000 bar). The resulting samples were analysed for their peptide content and the most promising fermented samples were further characterised. Microbial growth and the absence of cytotoxic effects were confirmed in the intestinal cell lines Caco-2 and HT-29 using the MTT assay. In addition, the protective role of these samples against SDS-induced inflammatory stress and their anti-in- flammatory potential in Caco-2, HT-29 and RAW264.7 macrophage cells were evaluated by measuring nitric oxide (NO) production. The results showed that the fermentation process, which was influenced by both microbial strain selection and HPH treatment, resulted in the production of peptide-rich samples with different functional proper- ties. These results support the potential application of fermented BSG as a source of functional ingredients.