Integrated metabolomics and peptidomics to delineate characteristic metabolites in milk fermented with novel Lactiplantibacillus plantarum L3

Abstract

A novel wild-type Lactiplantibacillus plantarum (L. plantarum) L3 with good fermentation characteristics and protein degradation capacity was isolated from raw milk samples. In this study, the metabolites in milk fermented with L. plantarum L3 were investigated by metabolomic and peptidomics analyses. The metabolomics results revealed that the metabolites in milk fermented with L. plantarum L3 were Thr-Pro, Val-Lys, l-creatine, pyridoxine, and muramic acid, which improved the taste and nutritional qualities of the milk. Moreover, the water-soluble peptides derived from L3 fermented milk exhibited high antioxidant properties and angiotensin I-converting enzyme inhibitory (ACEI) activities. Additionally, 152 peptides were found using liquid chromatography-mass spectrometry (LC-MS/MS). Furthermore, endogenous enzymes secreted by L. plantarum L3 cleaved β- and α-casein to release six ACEI peptides (ACEIPs), nineteen antioxidant peptides (AOPs), and five antimicrobial peptides (AMPS). Overall, these findings could be valuable in improving the quality of fermented milk.

Keywords: Bioactive peptides; Enzyme cleavage site; Fermented milk; Lactiplantibacillus plantarum L3; Metabolites.

Graphical abstract

Fig. 1

Metabolic pathway regulated by metabolites significantly different between L3 and LBST fermented milk. Note: Each bubble in the graph represents a KEGG pathway; the horizontal axis indicates the relative importance of metabolites in the pathway; the vertical axis represents the enrichment significance of metabolites involved in the pathway-ln (P-value); the bubble size represents the impact value of a given metabolite.

Fig. 2

The fingerprint of characteristic metabolites of L. plantarum L3 fermented milk.

Fig. 3

The profile of WSP in L3 and LBST fermented milk. (A) Venn diagrams of WSP in L3 and LBST fermented milk. The peptides derived from the parent proteins α_s1, α_s2, β and κ-CN among peptides in milk fermented by L3 (B) and LBST (C); Amino acid composition of peptides identified in L3 (D) and LBST (E) group; MW distribution of the peptides identified in L3 (F) and LBST (G) group. L3: L. plantarum L3 fermented milk; LBST: Lactobacillus bulgaricus and Streptococcus thermophilus fermented milk.

Fig. 4

In vitro biological activity of the WSP in L3 and LBST. (A-B) ABTS•+ scavenging activity; (C-D) DPPH• scavenging activity; (E) Restoration capacity RP; (F-G) ACE inhibition activity; Bars with different letters (a–c) are significantly different (P < 0.05). L3: L. plantarum L3 fermented milk; LBST: Lactobacillus bulgaricus and Streptococcus thermophilus fermented milk.

Fig. 5

The cleavage sites in α_S1- (A), α_S2- (B), β- (C) and α-CN by enzymes secreted by L. plantarum L3 (D); BPs in L. plantarum L3 fermented milk (E). → represents the digestion site, each → represents one digestion; bold red letters are angiotensin I-converting enzyme inhibitory peptides; bold blue letters are AOPs; bold yellow letters are antimicrobial peptides; bold green letters are dipeptidyl peptidase-IV inhibitory peptides; bold purple letters are immunomodulatory peptides.

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