Edible filamentous fungi (mycoprotein) represent a promising, circular protein source capable of valorizing industrial sidestreams. However, their nutritional value, particularly protein digestibility and mineral accessibility, requires detailed investigation. Therefore, several species of filamentous fungi were examined for their in vitro protein digestibility and mineral accessibility compared to conventional food proteins. Two primary research questions guided this study: firstly, whether filamentous fungi exhibit comparable protein digestibility to common food proteins, despite the presence of the fungal cell wall, which might hinder digestibility; secondly, investigating if fungi have superior mineral accessibility compared to plant-based ingredients like oats, as they lack antinutrients, such as phytic acid. 

All filamentous fungi were cultivated in-house by submerged fermentation using bioreactors. In vitro digestibility analyses utilized the standardized INFOGEST 2.0 in vitro gastrointestinal digestion protocol, assessing protein digestibility through the degree of hydrolysis and amino acid accessibility. Mineral accessibility was similarly assessed based on mineral solubility in the intestinal digests. 

Initially, five fungi species were cultivated to evaluate the quantity, quality, and digestibility of their proteins against fish, chicken breast, beef, and casein. Although lower total protein content, filamentous fungi demonstrated amino acid profiles comparable to the conventional proteins, being notably rich in lysine. Contrary to the initial hypothesis regarding the hindrance of fungal cell-wall on protein digestion, filamentous fungi exhibited protein digestibility comparable to conventional food proteins. However, the fungi species and cultivation media, particularly the presence of polyphenol, could significantly influence their protein digestibility. Additionally, prolonged cultivation substantially reduced fungal protein content, while only slightly decreasing the protein digestibility. 

Filamentous fungi mineral content and mineral accessibility are highly affected by the cultivation media. Mineral accessibility was higher in biomass cultivated on defined glucose media compared to oat-based media, the latter showing minor antinutrient effects despite low phytic acid levels. A later study indicated that fungal mineral composition and accessibility depended significantly on the cultivation media minerals concentration, reflecting the complex mechanism of fungal mineral homeostasis. Moreover, polyphenol-rich media, such as grape marc, significantly raised biomass polyphenol levels and reduced its mineral accessibility. 

In conclusion, filamentous fungi demonstrate robust nutritional potential with protein digestibility and mineral accessibility. However, their nutritional digestibility significantly depends on the fungi cultivation, underscoring their potential to be further optimized to maximize protein and mineral accessibility.