Screening of a Gossypol-Degrading Fungus and Its Application in Detoxification and Quality Improvement of Cottonseed Hulls

Cottonseed hull is an abundant and low-cost cotton processing byproduct, but its feed application is severely limited by free gossypol. This study screened a gossypol-degrading fungal strain from naturally fermented cottonseed hulls and soy sauce koji, and evaluated its detoxification and feed improvement effects via solid-state fermentation. Strain TM-2 was identified as Aspergillus oryzae. It degraded over 60% of gossypol in liquid fermentation and 69.54% in cottonseed hull solid-state fermentation. Genome annotation revealed 409 CAZyme genes and key pathways for naphthalene and aromatic compound degradation. After fermentation, crude protein and acid-soluble protein were significantly increased, while cellulose, hemicellulose, lignin, neutral detergent fiber, and acid detergent fiber were notably reduced. Antioxidant activity was also greatly enhanced. Secretomic analysis identified 92 extracellular proteins, including hemicellulases, cellulases, proteases, and peptidases that jointly promoted detoxification and quality improvement. A. oryzae TM-2 efficiently degrades gossypol and improves feed quality, showing high value in fermented feed development and agricultural byproduct utilization.