Study On Solid State Fermentation Process Of Prebiotics Fermented Soybean Meal

The novel solid state fermentation processes of prebiotics fermented soybean meal was investigated in this study.Firstly, prebiotics fermented soybean meal was produced by Aspergillus oryzae and Lactobacillus plantarum WZ011, respectively. The medium components and cultivation conditions of solid state fermentation by Aspergillus oryzae were optimized. The optimal medium composition and fermentation conditions were as follows:puffing soybean meal through 40 mesh, bran 9%, ammonium sulfate 3.6%, initial water content 51% and spore inoculum 29%(v/w). Under these conditions, 54.66% crude protein,1196.4 U/g neutral protease,9.9 g/100 g soluble protein and 84.1 mg/g free amino acid were achieved. The scaled-up fermentation suggested that 28 mm bed height and stationary cultivation on trays were the best choice. The optimal medium components and cultivation conditions of high density culture of Lactobacillus plantarum WZ011 were as follows:4%(v/v) inoculum volume; 4% sucrose; 5% yeast extract; 1.5% diammonium phosphate. After batch fermentation, the number of viable count reached 5.1×109 cfu/mL Fed-batch fermentation is the best high density cultivation strategy, OD540 and the number of viable count reached 32.8 and 7.8×109 cfu/mL respectively. Fed-batch fermentation was investigated in the 5 L fermentor. After supplementing concentrated nutrient solution two times, OD540 reached 40 and the number of viable count reached 1.89×1010 cfu/mL.Further study on mixed fermentation of Aspergillus oryzae and Lactobacillus plantarum WZ011 was investigated. Lactobacillus plantarum was inoculated after 36 h fermentation of Aspergillus oryzae and initial water content of aerobic phase was 51%. Inoculum volume of Aspergillus oryzae and Lactobacillus plantarum was 4% and 27%(v/w), respectively. Water content was 58% and starch content was 2% during anaerobic phase. The fermentation time was prolonged 84 h and the number of Lactobacillus plantarum viable count reached 6.5×1010 cfu/g. Compared with the initial number of viable count, Lactobacillus plantarum viable count increased by 432.3%, soluble protein reached 7.18 g/100 g, and free amino acid was 248.5 mg/g, increased by 69.1%.After aerobic fermentation by Aspergillus oryzae for 36 h, water content was controlled in 58-63% and fermented soybean meal was hydrolyzed for 10 h at 55 ℃. Soluble protein was increased by 36.1%, free amino acid was increased by 50.5% and small peptide content was increased from 8.1% to 13.4%, which was increased by 65.4%.Finally, in order to compare nutritional quality of fermented soybean meals of five different processes, various indexes were examined. The results demonstrated that soybean meal nutritional quality could be improved effectively through Aspergillus oryzae fermentation and treatment by high temperature hydrolysis. However, the effect of high temperature hydrolysis treatment was adverse in a fermentation process in series by Aspergillus oryzae and Lactobacillus plantarum WZ011. The fermented soybean meal was optimal in nutritional indexes when it was inoculated anaerobically by Lactobacillus plantarum WZ011 after aerobic fermentation by Aspergillus oryzae. Its trypsin inhibitor content was reduced by 91.8%, compared with raw soybean meal. It also contains 8.01% small peptides,4.95% lactic acid,0.317mg/g y-aminobutyric acid and 1.93×1010 cfu/g L. plantarum viable count. Besides, the fermented soybean meals contained abundant animal required trace elements, and the content of cadmium and lead was below national standard. Furthermore, they had bacteriostatic effects on some pathogenic bacteria. In conclusion, the fermented soybean meals had higher quality than those sold in the market.