Nutritional value assessments of peanut hulls and valorization with exogenous fibrolytic enzymes extracted from a mixture culture of Aspergillus strains and Neurospora intermedia

Peanut hulls are abundant waste with high bioactive compounds, antioxidant activity, and cell wall polysaccharides but low nutritional value. The aim of this study was to valorize this agricultural waste into alternative ruminant feed with exogenous fibrolytic enzymes (EFE) produced by fermentation of mixture culture of Aspergillus strains ( A. niger , A. tubingensis , A. oryzae , and A. sojae ) and Neurospora intermedia . Peanut hulls were pretreated for 24 h with increasing EFE levels 0, 1, 2, and 4 mg/g dry matter. The results showed that the effectiveness of this additive depended on EFE level. The low EFE level did not affect their nutritional value. The moderate and high EFE levels converted part of their cell wall polysaccharide compound into non-fiber carbohydrates and solubilize their organic matter without altering their bioactive compounds and their antioxidant activity. Consequently, these two levels of EFE accelerate rumen fermentation process, reduce the time of onset of rumen fermentation, and improve cell wall polysaccharide digestibility, net energy lactation, and short-chain fatty acid production. However, only the high EFE level promoted the proliferation of rumen protozoa and the amount of fermentation and dry matter digestibility and reduced rumen ammonia nitrogen by conversion into microbial crude protein. In conclusion, this practical bioprocess with the highest EFE level can be used as an effective tool for bioconversion of these wastes into energy feeds with high bioactive compounds and antioxidant activity to substitute expensive ruminant feeds. This strategy can provide a new source of revenue for the peanut shelling and peanut oil industries and protect the environment from the pollution. Graphical Abstract