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

¹Bioprocessing and Renewable Energy Laboratory, Department of Grain Science and Industry, Kansas State University, 1980 Kimball Ave., Manhattan, KS, 66502, U.S.A. ²Corresponding author. Phone: (785) 532-5011. Fax: (785) 532-7193. E-mail: vadlani@ksu.edu

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.