| The solid-state fermentation of soybean meal by mixed yeast, Aspergillus oryzae,lactic acid bacterial and Bacillus subtilis was studied using one-step method. Through orthogonal experiment, the optimal inoculation ratio of yeast, Aspergillus oryzae, lactic acid bacterial and Bacillus subtilis was determined as 1∶3∶1∶3. The fermentation conditions of soybean meal were optimized by response surface methodology as follows: initial temperature 32.4℃, content of water 45.8%, amount of inoculation 12%. Under the optimal fermentation conditions, the content of small molecular peptides increased from 1.22% to 5.41% and the content of crude protein improved from 46.0% to 55.1% in fermented soybean meal. The analysis results of SDS-PAGE and physical characteristics of fermented soybean meal showed that almost all the macromolecular proteins of fermented soybean meal were degraded to small molecular peptides with relative molecular weight less than 14.4 kDa, and the fermented soybean meal had strong acid smell and mellow flavor. |
