Bio-modification of soybean meal with Bacillus subtilis or Aspergillus oryzae

The nutritional quality of soybean meal (SBM) was improved via solid-state fermentation using the Aspergillus oryzae or Bacillus subtilis microbes in conical flasks. Compared to the control, the protein content in fermented soybean meal (FSBM) was increased by 8.37% and 0.34% with B. subtilis and A. oryzae, respectively, and their trypsin inhibitor contents were reduced by 96% and 82%, respectively. Furthermore, the concentrations of small-size proteins in FSBM were increased from 5% to 63% and from 5% to 35% by B. subtilis and A. oryzae, respectively, while the concentrations of large-size proteins were reduced from 40% to 2% and from 40% to 8%, respectively. Significantly lower levels of antigenic proteins were observed in FSBM compared to SBM. Also, FSBM exhibited a higher level of DPPH free radical-scavenging activity than did the control. The in vitro digestibility of crude protein by pepsin (IVDI) was increased strongly by fermentation. Fermentation with B. subtilis mediated a higher IVDI than did fermentation with A. oryzae. However, the in vitro digestibility of crude protein by pepsin and trypsin (IVDII) derived from B. subtilis and A. oryzae showed no significant difference from that of the control. In general, the protein content and anti-oxidation activity were increased and trypsin inhibitors and antigenic proteins were reduced in FSBM culture, indicating that it could be used as a new protein source in animal diets.