Changes in nutritional and antinutritional aspects of soybean meals by mechanical and solid-state fermentation treatments with Bacillus subtilis and Aspergillus oryzae

There has been strong evidence among previous experiments that heat treatment and/or fermentation could effectively eliminate antinutritional factors (ANF) and enhance the protein quality of soybean meal (SBM). However, the efficacy varies among microbial inoculants used and some ANF remains. Here, we investigated whether there is a synergistic effect between Bacillus subtilis and Aspergillus oryzae as inoculants to enhance the quality of SBM in two- steps of mechanical and solid-state fermentation (SSF) processing. The results showed that there was an obvious improvement on protein and amino acids contents of SBM after SSF. B. subtilis + A. oryzae reduced phytic acid, tannin, and saponin of SBM to a very low amount as well as increased total phenolic compound concentration and DPPH antioxidant activity. It concludes that under two-step SSF, B. subtilis and A. oryzae synergistically enhanced nutritional aspects and decreased ANF content of SBM than the one-step SSF. [Display omitted] •Solid state fermentation enhanced protein and amino acids contents of SBM.•B. subtilis resulted in a greater effect to increase protein and AA than A. oryzae.•Steam conditioning had no substantial effect on the nutritional aspects of SBM.•SSF reduced phytate and increased phenolic compound and antioxidant activity of SBM.•Two-step SSF had greater improvement than one-step SSF on SBM.