| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 107 === Soybeans are rich in proteins, lipids, variety of bioactive compounds and beneficial for human health. Soybean meal (SBM) is the by-product of soybean after oil extraction and can be used as a protein source in animal feed. However, effective use of high nutritional soybean meal is still limited due to its anti-nutritional factors (ANFs), which lead to less nutrient absorption, allergic diarrhea and immunity problems. In feed industry, these problems are often solved by partial replacement of SBM with lacto-fermented soybean meal (LFSM). However, its health promoting mechanism is still not clear. Therefore, the aims of this study were to investigate the possible health-promoting effects of LFSM and identify the major bioactive components which are responsible for the health benefits. Four lactic acid bacteria, including L. acidophilus, L. plantarum, L. salivarius, L. helveticus were used for fermentation. Three health problems, including nutrients uptake, allergic diarrhea and immune function were simulated using three in vitro cell models (murine macrophages, rat intestinal epithelial cells, rat basophils). Possible bioactive components of the fermentation product were analyzed simultaneously. Multivariate linear regression analysis was used to compare their relevance. The results showed that LFSM could significantly inhibit nitric oxide production on LPS-activated RAW 264.7, and L. helveticus-LFSM had the highest (67~77%) inhibition rate at high concentration. On the other hand, LFSM also promoted the secretion of nitric oxide of RAW 264.7. L. plantarum-LFSM had the best effect, which induced 8~13 μM of nitric oxide secretion at high concentration. The LFSM also recovered the TEER value and alleviated dagranulation reaction in the LPS-induced IEC-6 cells and IgE sensitized RBL-2H3 cells, respectively. Thus we could conclude that LSFM has health promoting effects including immune modulation, enhancing the integrity of the epithelial barrier, and alleviation of degranulation in vitro model.
In this study, the content of peptides, organic acids, extracellular polysaccharides and ANFs were also analyzed. All of the four lactic acid bacteria could effectively degrade the main allergens (β-conglycinin and glycinin), phytic acid and oligosaccharides (raffinose and stachyose). Immune modulation effect (stimulating nitric oxide secretion and inhibiting LPS-induced high amount of nitric oxide) is the most prominent bioactivity among the activities investigated. Based on our results with multivariate linear regression statistical analysis and information from literatures, we could conclude that there are multiple bioactive components to regulate a physiological activity. The peptide content is the most significant factor correlated with immune modulation activity. In order to clarify the effect of the peptide in LFSM on immune modulation, L. helveticus and L. plantarum were used for fermentation and proteolytic enzymes (protamex and bromelain) were also added during fermentation to increase the yield of the peptides. The results showed that the longer the hydrolysis time, the higher the peptides content in the fermented products. However, the immune activity of the fermentation/enzyme hydrolyzed products was still lower than that of LFSM without protease hydrolysis. We suspect that the peptide has structural specificity for immunomodulatory activity, and the specific amino acids composition and size of the peptides would influence their bioactivity. Addition of protease may have altered the structure of the peptides, in turn, their bioactivities. Further, exogeneous enzyme may also affect the enzyme system of lactic acid bacteria acting on the protein and the peptide. Nevertheless, these results confirmed that the peptide is one of the major factors affecting the bioactivity.
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