Untargeted Metabolomics Reveals Shared and Unique Metabolites in <i>Bifidobacterium</i> and <i>Lactobacillus</i> Derived Postbiotics

The concept of postbiotics has sparked interest in their functions, but their complex composition from various bacterial sources requires further study. Cell-free supernatant (CFS), the most intricate component, needs more research to pinpoint bioactive elements. An untargeted metabolomic analysis identified 3333 metabolites from 14 probiotic strains. This study examined similarities and differences among these strains, finding 1262 metabolites shared across all postbiotics, 62.5% linked to microbial metabolism, mainly amino acids. Principal component analysis revealed notable differences between <i>Bifidobacterium</i> and <i>Lactobacillus</i> CFSs. <i>Bifidobacterium</i> CFS had a higher amino acid and peptide metabolite content (48.44%) compared to <i>Lactobacillus</i>, with a prevalence of glutamic acid peptides. Indole derivatives, crucial for immune modulation via the aryl hydrocarbon receptor, were found in all CFS strains. Notably, 3-indoleacrylic acid was more concentrated in <i>Lactobacillus</i>, while indole-3-lactic acid was more prevalent in <i>Bifidobacterium</i>. This study offers a detailed analysis of postbiotic-active substances, aiding future research.