Catabolite Repression and Substrate Induction as Strategies for Protease Production in Edible Mushrooms

Edible mushrooms are an underexplored source of industrial proteases, whose synthesis is highly dependent on the cultivation substrate. This study investigated the effect of nine culture media on the proteolytic profiles of Auricularia sp., Lentinus sp., Macrocybe sp., and Grifola frondosa. Fungi were cultivated on diverse media (e.g., Czapek, Malt, Soy Flour). We analyzed total protein, specific activities (total, cysteine, serine proteases) using a biochemical assay, and protein secondary structure via FTIR, with metabolic patterns identified by PCA. A dissociation was found between total protein yield (highest in MFI/Casein media) and specific activity (highest in maltose media), suggesting catabolite repression. Distinct metabolic strategies emerged: Grifola frondosa specialized in serine protease production in the minimal Czapek medium (catabolic derepression), while Macrocybe sp. maximized cysteine protease production on soy flour (substrate induction). FTIR confirmed this, revealing a β-sheet-dominant (75.5%) structure for Grifola extract versus a random-coil-dominant (60.8%) structure for Macrocybe. This study provides a framework for mechanism-based bioprocess design, enabling the tailored production of serine proteases from G. frondosa (Czapek medium) or cysteine proteases from Macrocybe sp. (soy medium) for customized biotechnological applications.