Probiotic Evaluation of Lactic Acid Bacteria Isolated from Conventional Sources

Abstract

Probiotic bacteria represent the good bacteria that impart health benefits. Lactic acid producing bacteria called as LAB are commonly used as probiotics as they have long history of safe use in food. The present study aimed to evaluate bacterial isolates from curd, cow’s milk and breast milk thereby determining its potential to be used as probiotics. Out of 108 isolates, eight strains showed phenotypic characteristics similar to that of lactic acid bacteria and were investigated further. The tolerance for low pH, different concentrations of bile and phenol and resistance to the simulated gastrointestinal and salivary conditions were studied in detail for these strains. Haemolytic activity of the strains and their susceptibility to antibiotics were tested.  Strains were also evaluated for probiotic properties including adherence to the Caco-2 cells and antagonistic activity against pathogens. All the strains showed tolerance to acidic pH, bile salts, phenol, lysozyme, pepsin and also successfully adhered onto the Caco-2 cells invitro. The cell-free supernatant (CFS) of the strains exhibited antioxidant activity by scavenging 1,1-Diphenyl-2-Picryl-Hydrazil (DPPH) radicals and showed antimicrobial activity against pathogenic strains like Salmonella typhi, Pseudomonas aeruginosa and Escherichia coli. The three strains with profound probiotic activity were identified using 16s rRNA sequencing as Weissella confusa C8 from curd, Lactobacillus paracasei MK2 (Lacticaseibacillus paracasei MK2) from milk, and Staphylococcus epidermidis BM4 from breast milk. Hence, these three isolates from the above sources can be considered   as strains having good probiotic traits with antibacterial activity.