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Soybean peptides were reported to promote the growth and metabolism of Lacticaseibacillus rhamnosus (L. rhamnosus) Lra05. However, the relationship between L. rhamnosus Lra05 and the characteristics of soybean peptides is still unclear. Therefore, digested soybean peptides (dPEP) after 36 h utilization by L. rhamnosus Lra05 were identified and analyzed. We found that L. rhamnosus Lra05 tends to utilize hydrophobic peptides with three to five amino acids residues, and hydrophilic peptides with more than five residues. They also prefer peptides with proline at penultimate C-terminal position or arginine at ultimate C-terminal position. Moreover, fraction 1 (F1) and fraction 7 (F7) acquired from dPEP using RP-HPLC exhibited the strongest growth and metabolism promoting effects, and the utilized characteristics of F1 and F7 were similar with those of dPEP. These results explained why soybean peptides could promote L. rhamnosus to some extent and strengthen theoretical basis for the application of soybean peptides as potential prebiotics.

Lactic acid bacteria are one of the most pivotal probiotics. Promoting their viability could be an effective method to modulate the balance of intestinal flora, thereby improving human health. The current solution is to take advantage of carbon-sourced prebiotics, while protein and peptides with potential prebiotic functions have not been investigated. Soy proteins and peptides have been proven to enhance the growth and metabolism of Lactobacillus. However, research on the relationship between strains of lactobacilli and the structure of soybean peptides is still limited. In the present study, soybean protein and peptides effectively increased the growth and organic acid secretion of Limosilactobacillus reuteri LR08. Additionally, soybean peptides and fructooligosaccharides showed synergistic effects in modulating Limosilactobacillus reuteri LR08. Fraction 1 acquired from soy peptides using RP-HPLC exhibited the most effectiveness and several novel peptides were identified. These results could theoretically and practically benefit soybean peptide application as a potential prebiotic.