Lactobacillus fermentum SNR1: Probiotic efficiency and characterization of the antimicrobial peptide against dental caries and foodborne pathogens

In this study, fermented rice gruel, a traditional food in South Telangana, India, was used as a source for the isolation of biologically significant probiotics. A total of 56 morphologically diverse strains were isolated and screened for their ability to inhibit dental biofilms as well as foodborne and aquaculture bacterial pathogens. Among these, isolate SNR1 was selected for further characterization due to its potential antimicrobial activity against bacterial pathogens such as Streptococcus mutans, Listeria monocytogenes, Staphylococcus aureus, Vibrio parahaemolyticus and Salmonella typhi. The results of 16S rDNA sequencing showed that isolate SNR1 was closely related to Lactobacillus fermentum strains from different sources. The bacteriocin peptide with potential activity was extracted and purified from the cell-free supernatant using ammonium sulphate precipitation, gel permeation chromatography and reversed-phase high performance liquid chromatography (RP-HPLC), and was named peptide SNR1. Tricine SDS-PAGE followed by MALDI-TOF-MS analysis revealed that the purified peptide had a molecular mass of 4.33 kDa, with the N-terminal sequence identified as MPTTSHFHLSPQGK. The purified peptide SNR1 showed good stability with various physiological enzymes, temperatures and pH conditions.