In vitro protein digestion and mineral accessibility of edible filamentous fungi cultivated on winery and distillery by-products

Edible filamentous fungi (mycoprotein) offer a sustainable protein source that supports the upcycling of agri-food industry sidestreams, stimulating circular production systems. This study evaluated the nutritional quality, including protein digestibility and mineral accessibility of three edible fungal species Neurospora intermedia (NI), Aspergillus oryzae (AO), and Rhizopus oryzae (RO), cultivated on winery by-products (grape marc, wine lees, and vinasse) and on synthetic glucose medium as a control. Protein content, amino acid profile, essential minerals, in vitro protein degree of hydrolysis (DH%), and mineral accessibility were assessed. One important hypothesis explored was whether enriched fungal biomass polyphenol levels would negatively influence protein digestibility and mineral accessibility. Wine lees supported the highest biomass protein content (27.2–30.6 % dry weight, dw), followed by grape marc, and vinasse. The amino acid profile revealed that essential amino acids comprised 40.88–51.69 % of the total protein, with lysine (8.43–14.18 %) and leucine (7.62–9.95 %) being the most abundant. Notably, RO grown in grape marc accumulated higher polyphenol level compared to NI and AO, up to 96 mg gallic acid equivalent/g dw. After in vitro digestion, NI and AO revealed higher protein digestibility than RO (38–80 % vs 9–53 % DH), and all fungal species cultivated in wine lees—particularly RO—exhibited the highest levels of accessible iron and zinc Grape marc-grown RO showed significantly reduced protein digestibility and mineral accessibility. These findings present a promising route to produce mycoprotein, while lowering the wine and distillery sector footprint. Polyphenol levels should be optimized to avoid hampering protein digestibility and mineral accessibility. • Filamentous fungi grown on wine lees showed higher protein content. • Neurospora intermedia and Aspergillus oryzae had high protein digestibility. • Rhizopus oryzae accumulated more iron than other fungal species. • Rhizopus oryzae grown on grape marc had significantly higher polyphenols. • Rhizopus oryzae grown on grape marc showed lower DH% and Fe and Zn accessibility.