Nitrogen Source Screening on Agar Medium Followed by Submerged Cultivation of Pleurotus albidus Mycelium for Nutritional and Amino Acid Characterization.

The search for sustainable protein sources has increased interest in filamentous fungi, however, most studies focus on a limited number of established species. Pleurotus albidus, a basidiomycete native to South America, remains little explored for food applications, particularly regarding the nutritional characterization of its mycelium. In this study, P. albidus was initially cultivated on PDA agar supplemented with yeast extract (YE) or ammonium sulfate (AS) at 0.5-2 gN/L for nitrogen source screening. On agar medium, YE reduced the lag phase and accelerated plate colonization, reaching full plate coverage in 8-9 days compared to 11-12 days for AS. Based on these results, the selected condition was subsequently applied to submerged cultivation in which the mycelium grew as spherical pellets and reached 12.4 g/L after 12 days, with 23.8% protein, 26% fiber, and 39% carbohydrates. Chemical score analysis indicated that most essential amino acids (EAAs) exceeded recommended levels; however, sulfur-containing amino acids (methionine + cystine) were limiting (0.6). Threonine showed the highest score (2.3), while lysine (1.2) and tryptophan (1.1) also scored above 1.0. Non-essential amino acids such as glutamic (145 mg/g) and aspartic acid (102 mg/g) predominated. These results highlight the nutritional potential of P. albidus mycelium as a novel protein source and support its further investigation for future food applications, while additional studies on protein digestibility and cultivation optimization are needed to further improve amino acid balance and protein quality.