Metabolomics study on fermented soybean meal by Rhizopus oligosporus RT-3 and its improvement on the growth status of malnourished mice

Abstract

Abstract In this study, Rhizopus oligosporus RT-3 was utilized to ferment soybean meal to obtain a tempe-like food with low fat and high bioactivity. To investigate the impact of fermentation on soybean meal’s nutritional value, we detected the protein-related indices and conducted a non-targeted metabonomic analysis on both fermented soybean meal (FSM) and soybean meal (SM) in order to explore changes in a certain type of metabolite and its corresponding metabolic pathways. The results showed a significant increase in crude protein, peptides and amino acids while getting porous after fermentation. A reduction of raffinose and stachyose to 18.1% and 8.5%, respectively, due to the action of α-galactosidase and β-furanofructosidase occurred. As to amino acid metabolites, essential amino acids for human bodily functions such as lysine, histidine, and threonine were significantly upregulated. Furthermore, nine peptide metabolites were identified as angiotensin-converting enzyme (ACE) inhibitors and dipeptidyl peptidase-4 inhibitors (DPP-IV). After feeding with different doses of FSM, levels of insulin-like growth factor-1 (IGF-1), hemoglobin (HB), albumin (ALB), and total protein (TP) of malnourished mice all returned to normal. In conclusion, fermentation with Rhizopus oligosporus RT-3 can improve the quality of SM by reducing the level of oligosaccharide anti-nutrition factors and increasing the contents of free amino acid and small bioactive peptides, which provide a theoretical basis and new ideas for the application of FSM. Graphical Abstract