Improvement of nutritional value and bioactivity of soybean meal by solid-state fermentation with Bacillus subtilis

The main objective of this research was to evaluate the nutritional quality and bioactivity of soybean meal (SBM) by solid-state fermentation (SSF) with Bacillus subtilis. The results indicated that the contents of crude and soluble proteins, total phenol and flavonoid all increased distinctly, while trypsin inhibitor (TI) content decreased after fermentation. There was a slight difference in the total amino acids TAA profile between SBM and fermented soybean meal (FSBM), while the free amino acids (FAA) differed significantly. The result of high performance capillary electrophoresis analysis indicated that there were more soluble components in FSBM than that in SBM. Analysis of antioxidant activities showed that the reducing ability, scavenging DPPH and ABTS radical abilities of FSBM were all stronger than that of SBM. In addition, FSBM has been found having a strong inhibition on angiotensin I-converting enzyme (ACE) measured by HPLC revealing FSBM has antihypertensive activity. These results suggest that SSF with Bacillus subtilis can substantially improve both the nutritional quality and bioactivity of SBM.