Valorization of Bread Waste Hydrolysates and Plant-Based Nitrogen Sources for Mycoprotein Production by Pleurotus salmoneostramineus

Mycoprotein production by Pleurotus salmoneostramineus was evaluated using the bread industry by-products wheat bran hydrolysate (WBH) and stale bread hydrolysate (SBH) as carbon sources, with mung bean protein isolate hydrolysate (MBH) as a nitrogen source, within a circular bioeconomy framework. Enzymatic hydrolysis effectively converted these food industry waste streams into fermentable substrates with complementary nutritional profiles: SBH provided the highest total sugar content (57.53 g/L), while MBH contributed the highest total nitrogen (3.58 g/L) and essential amino acid content (215.05 mg/100 mL). Of 11 WBH:SBH ratio formulations evaluated under static cultivation, WB4 (WBH:SBH 70:30; C/N 27.32:1) was identified as the optimal carbon source formulation, producing the highest biomass (3.46 g/L) and protein content (23.19 g/100 g) after 14 days. Subsequent nitrogen source optimization under dynamic cultivation (200 rpm, 5 days) showed that MBH supplementation at 5 g/L produced the highest biomass (16.59 g/L), protein content (66.71 g/100 g), and absolute protein production (11.07 g/L). The amino acid profile of mycoprotein produced under optimized conditions met or exceeded the FAO/WHO-recommended essential amino acid requirements for older children, adolescents, and adults; the essential amino acid content (354.72 mg/g protein) was comparable to soy protein isolate and exceeded that of wheat gluten. Mycelial morphology shifted from filamentous networks under static conditions to fragmented clump structures under dynamic cultivation with MBH supplementation. These findings indicate the feasibility of producing nutritionally complete mycoprotein from food industry waste streams, with potential applications in plant-based food formulations.