Valorization of Caragana korshinskii Kom. using cooperative Aspergillus oryzae and Saccharomyces cerevisiae to produce fermented feed protein

Caragana korshinskii Kom. represents a substantial biomass resource that can be converted into feed protein via microbial fermentation. This study aimed to improve the nutritional value of C. korshinskii through strain screening and substrate optimization. Amino acid content and in vitro digestibility were systematically investigated. Astral-DIA proteomics was employed to compare protein enrichment mechanisms underlying screened microbial involvement in substance conversion. The Aspergillus oryzae and Saccharomyces cerevisiae co-culture increased the true protein content of the optimized substrate by 50.6% to 67.9%, while the highest nitrogen conversion ratio (69.5%) was achieved with low-level supplementation of (NH₄)₂SO₄. The relative abundances of hydroxyproline and lysine content increased by more than twice in the mixed fermentation. Proteomics analysis identified 291 differentially expressed proteins in the mixed culture versus A. oryzae alone, enriched in ribosome biogenesis; valine, leucine and isoleucine biosynthesis; galactose metabolism; amino acids biosynthesis and sulfur relay system. This study provided guidance for the high-value utilization of C. korshinskii and elucidated the differential protein enrichment pathways between A. oryzae, S. cerevisiae and their cocktail in utilizing C. korshinskii.