Okara-F. venenatum mycelial composite (OFMC) produced by submerged fermentation: Nutrition, microstructure, and...

Okara is a nutrient- and fiber-rich soybean side stream, yet its direct use in structured foods is limited. In this study, we developed a submerged fermentation process that converts okara into a food-relevant Okara-F. venenatum mycelial composite (OFMC) prototype designed for use as a whole-fermented composite material in plant-based foods. In baseline broth culture, Fusarium venenatum A3/5 mycelial dry mass peaked at 168 h. Increasing okara loading in the fermentation medium (0.5-2.5%, w/v) increased blank-corrected recovered composite solids from 2.71 ± 0.28% to 13.22 ± 0.69%. This value was interpreted as an operational indicator of fermentation-associated composite-solid recovery rather than purified fungal biomass yield. At the highest loading, crude protein increased from 17.93 ± 0.04% to 21.47 ± 0.81%. At 2.0-2.5% okara loading, IVPD increased to 0.99-1.00 and the untruncated estimated in vitro PDCAAS reached 1.06-1.09, corresponding to capped values of 1.00. SEM micrographs showed filamentous and layered morphological features in OFMC. In model plant-based formulations standardized to 75.0% final moisture, OFMC combined with 5% textured vegetable protein (TVP) showed a moderate-firmness and elastic-recovery profile under TPA conditions (hardness 8.74-10.52 N; springiness ∼0.20; resilience 1.08-1.13). Overall, OFMC suggests a practical proof-of-concept route for okara upcycling into a food-relevant, protein-containing, texture-relevant composite prototype for plant-based formulation development.