Evaluation of new candidate probiotic lactobacillus strains isolated from a traditional fermented food- multigrain-millet dosa batter

The food industry is constantly developing new products to meet the increasing global demand of fermented foods, for its health benefits. In this study, the potential probiotics in traditional fermented food - “multigrain-millet” based Dosa batter, and their significant probiotic characteristics was investigated. In addition, the ability of probiotic Lactobacillus to prevent foodborne pathogens was explored. A total collection of 70 isolates were examined from the batter. The six isolates with the best in vitro probiotic characteristics were studied. The six isolates MYSDS57, MYSDS68, MYSDV3, MYSDV2, MYSDV5 and MYSDV6 were identified as Lactiplantibacillus plantarum, Lacticaseibacillus paracasei, Lactobacillus pentosus, Lactiplantibacillus plantarum, Lactiplantibacillus plantarum and Limosilactobacillus fermentum respectively based on 16 S rRNA gene sequencing analysis. All six Lactobacillus were able to tolerate acidic pH (45 %–80 % survivability) and 0.3% bile salt (50 %–80.4 % survivability) up to 5 h of incubation. All tested strains showed higher growth at 37 °C, resistance to different concentrations of phenols (53.3 %–83.6 % of viability) and NaCl (38.2%–49.5% of viability). However, the strains exhibited resistance to antibiotic vancomycin, but no hemolytic and DNase activity. Moreover, six strains showed significantly high values of autoaggregation (54.6%-78.8 %) and cell surface hydrophobicity (70 %-81.7%). The α-glucosidase and α-amylase inhibitory activity ranged from 15.08% to 67.22 % and 50.15%–92.13% respectively. Additionally, the intracellular cell-free supernatant of all six Lactobacillus demonstrated antibacterial activity with the inhibition rate of 64.8 %–86 % (Salmonella typhi), 51.8 %–95.2 % (Escherichia coli), 59.9 %–76.6 % (Listeria monocytogenes), 39.6% −74.3 % (Salmonella paratyphi), 57.4 %–81.3 % (Klebsiella pneumonia), 44 %-67.1% (Staphylococcus aureus) and 7.2 %–54.7 % (Pseudomonas aeruginosa). The strains exhibited higher viability (5.8–7.5 log CFU/mL) to simulated gastric juice, high adhesion to chicken crop epithelial cells and buccal cells. These isolates also reduced the cholesterol level in vitro. Overall, the selected Lactobacillus can be considered promising probiotic candidates for future applications.