Nutritional Enhancement of Soy Meal via Aspergillus oryzae Solid-State Fermentation

Antinutritional factors in soy meal (SM) include trypsin inhibitor, galactooligosaccharides (GOSs), structural polysaccharides, and large-molecular-weight protein. These antinutritional factors limit the usage of SM for young monogastric animals. Aspergillus oryzae solid-state fermentation was applied to eliminate these factors, and changes in physical and chemical characteristics of SM were investigated. A. oryzae-treated SM was more nutrient dependent than oxygen dependent, which was illustrated by scanning electron microscopy. After 36 h of fermentation, the concentration of GOSs (raffinose, stachyose, and verbascose) and trypsin inhibitor decreased from an initial value of 9.48 mmol/100 g to a nondetectable level. Structural polysaccharides decreased by 59% (w/w), and the degree of hydrolysis of SM protein increased from an initial value of 0.9 to 7% (w/w) through the seven-day fermentation. Fermentation also modified nutritional factors. Protein content increased from 50.47 to 58.93% (w/w) after 36 h of fermentation. Amino acid contents were significantly enhanced. The research thoroughly studied the A. oryzae solid-state fermentation of SM, and the resulting premium product could provide a better protein source for monogastric animals.