Potential therapeutic biomolecules of Lactobacillus strains isolated from human milk microbiota

This study aimed to select the Lactobacillus strains, from human milk microbiota, with specific properties of synthesis of exopolysaccharides (EPS), S-proteins and bacteriocins with the potential to be characterised as therapeutic biomolecules. Detection of the „ropy“ phenotype was used for screening of EPS producers, while bacteriocinogenic activity was analysed by the determination of antagonistic activities in vitro. S-proteins of Lactobacillus brevis strains MB1, MB2, MB13 and MB20, were detected by SDS-PAGE analysis of GHCl extracted surfaceome and further analysed by LC-MS/MS using database search by Mascot. For the identification of the genes of interest, responsible for the expression of targeted biomolecules, PCR with specific primers was applied. 1H-NMR analysis confirmed that Lactobacillus fermentum MC1 strain produces EPS. PCR method with eps primers confirmed the genes of the eps cluster. Dendrograms of SDS-PAGE electrophoretic profiles, obtained using GelCompar II, showed characteristic bands of approximately 45 kDa in L. brevis strains identified by mass spectrometry. The spectrum of Lactobacillus strains showed bacteriocinogenic activity, however, the presence of plnJ, plnA and plnEF genes involved in the bacteriocin biosynthetic pathway was confirmed in the genome of six Lactobacillus plantarum strains. The comparative genomic analysis provided insights into the clusters related to the expression of potential biomolecules. The analysis of breast milk microbiota revealed the presence of Lactobacillus strains with the potential to express specific biomolecules. Further investigations will be directed towards deciphering mechanisms of probiotic actions triggered by these biomolecules in order to develop next-generation probiotics.