Preparation Of Soybean Peptides By Liquid State Fermentation

Soybean peptides, which could be a kind of potential function food, were applied widely in many areas. Soybean meal contains a great quantity of soybean protein, about 45.0%~55.0%. Soybean protein was a superior protein. It could be hydrolyzed into soybean peptides. However, some bitter components, affecting the flavour of products, would be produced after hydrolyzation of soybean protein. The methods of debittering used now were not only complicated but of high cost. The method cut down production cost, and accelerated the industrialization of functional peptides to produce peptides which combined hydrolyzing soybean protein and debittering in one-step with food-grade Bacillus subtilis1389 and Aspergillus niger3.350 or Aspergillus oryzae A-9005. There were no relative at home and abroad reports so far. This thesis focused on the following aspect: studied on the changes of physicochemical indices of soybean peptides preparede by Bacillus subtilis1389, Aspergillus niger3.350, Aspergillus oryzae A-9005 , Bacillus subtilis1389 in combination with Aspergillus niger3.350 and Bacillus subtilis1389 in combination with Aspergillus oryzae A-9005, make sure the single factors condition through the analyse of the dynamic fermentation results and do single factor tests. Then based on the single factor tests, by orthogonal test to determine the optimal process conditions by the indicator of soybean peptide's conversion; The results were as follows:First: Under the conditions of the volume of inoculation was 10%, 200rpm, the best fermentation conditions of producing protease by Bacillus subtilwas1389, was that the initial pH was 7.6, the soybean concentration was 6% at 31℃for 48h, and protease activity could reach 389.82U/mL; the best fermentation conditions of producing soybean peptides by Bacillus subtilwas1389, was that the initial pH was 7.4, the soybean concentration was 4% at 35℃for 48h and the soybean peptide's conversion could reach 88.19%.Second: Under the conditions of the volume of inoculation was 10%, 200rpm, the best fermentation conditions of producing protease by Aspergillus niger3.350, was that the initial pH was 5.6, the soybean concentration was 4% at 32℃for 48h, and the protease activity cold reach 27.05U/mL; the best fermentation conditions of producing soybean peptides by Aspergillus niger3.350, was that the initial pH was 5.8, the soybean concentration was 4% at 32℃for 48h, the soybean peptide's conversion could reach 60.73%.Third: Under the conditions of the volume of inoculation was 10%, 200rpm, the best fermentation conditions of producing protease by Aspergillus oryzae A-9005, was that the initial pH was 6.2, the soybean concentration was 2% at 32℃for 46h, and the protease activity could reach 24.68U/mL; the best fermentation conditions of producing soybean peptides by Aspergillus oryzae A-9005, was that the initial pH was 6.6, the soybean concentration was 2% at 32℃for 46h, the soybean peptide's conversion could reach 77.19%.Forth: Under the fermentation conditions of the volume of inoculation was 10%, 200rpm, natural pH for 48h, the best fermentation conditions of producing protease by Bacillus subtilwas1389 in combination with Aspergillus niger3.350, was that the ratio of inoculation was 3:2(Bacillus subtilwas1389: Aspergillus niger3.350), the soybean concentration was 3% at 32℃, and the protease activity could reach 186.09U/mL; the best fermentation conditions of producing soybean peptides by Bacillus subtilwas1389 in combination with Aspergillus niger3.350, was that the ratio of inoculation was 3:2(Bacillus subtilwas1389: Aspergillus niger3.350), the soybean concentration was 3% at 32℃, and the soybean peptide's conversion could reach 88.32%.Fifith: Under the fermentation conditions of the volume of inoculation was 10%, 200rpm, natural pH for 48h, the best fermentation conditions of producing protease by Bacillus subtilwas1389 in combination with Aspergillus oryzae A-9005, was that the ratio of inoculation was 3:2(Bacillus subtilwas1389: Aspergillus oryzae A-9005), the soybean concentration was 4% at 32℃, and the protease activity could reach 201.78U/mL; the best fermentation conditions of producing soybean peptides by Bacillus subtilwas1389 in combination with Aspergillus oryzae A-9005, was that the ratio of inoculation was 3:2(Bacillus subtilwas1389: Aspergillus oryzae A-9005), the soybean concentration was 4% at 32℃,and the soybean peptide's conversion could reach 89.07%.