Upcycling Oat Hulls into a Protein-Enriched Food Ingredient using Neurospora intermedia

To address sustainability challenges in the current food system and improve resource utilization, this study investigates the upcycling of oat hulls, a lignocellulosic by-product of oat processing, into a protein-enriched food ingredient through solid-state fermentation (SSF) with Neurospora intermedia. Fermentation conditions were systematically optimized, focusing on substrate composition, moisture content, temperature, and duration. The optimal setup consisted of a substrate where the dry material was composed of 80% (w/w) whole oat hulls and 20% (w/w) milled oat hulls, hydrated to 70% (w/w) water content, and incubated at 28 °C for 7 days. Under these conditions, the fermentation process demonstrated reproducibility, and the protein content of the fermented material increased from 6.8% to 13.9% in dry weight, accompanied by an increased proportion of essential amino acids. Although the fermented product did not exhibit distinct techno-functional improvements, its incorporation into a prototype food formulation contributed distinct flavor-related characteristics. These findings demonstrate the strong potential for protein enrichment of oat hulls through fungal fermentation and their subsequent applicability as a food ingredient. The promising initial results point to clear opportunities for further investigation and optimization to improve nutritional, functional, and sensory properties.