Probiotic potential of exopolysaccharide producing lactic acid bacteria isolated from homemade fermented food products

Abstract

In the current study, 41 bacterial isolates were obtained from homemade fermented food products (cheese, curd, fermented rice water, yogurt, and buttermilk). Among these bacterial isolates, 4 lactic acid bacteria (LAB) strains such as CH4, Sri3, Kri1, and R3 were screened based on their wide inhibitory potential against test indictors by the well diffusion method. Based on the morphological, biochemical and phylogenic characterization, the four selected probiotic LAB strains were identified viz., Lactococcus hircilactis strain CH4, Lactobacillus delbrueckii strain GRIPUMSK, Lactobacillus johnsonii strain PUMSKGRI, and Lactobacillus leichmannii strain SKGRIPUM. These 4 probiotic LAB strains exhibited 62.5–87.5% antibiotic sensitivity, non-haemolytic, thereby confirming their safe status. All of these strains were found to be extremely acid tolerant after 5 h at pH 2–3. These 4 strains were able to withstand 2% high bile salt concentrations for 5 h with a survival rate of 67.40–73.68%. After 5 h, all four isolates demonstrated good auto-aggregation capacity of greater than 40% and strong hydrophobicity towards xylene of greater than 40%. All the four selected isolates have produced antimicrobial metabolites of exopolysaccharides (196.4 U/mL- 217.9 U/mL), H2O2 (0.49–0.71 g L−1) and β-galactosidase (196.4–217.9 U/mL). These strains exhibited the ability to assimilate cholesterol ranged between 12.15 and 79.72%. Moreover, they were found to be highly potential, with a total score of 95.83%, and are now being used to make probiotic food products. Hence, this work affirms the use of selected four LAB strains as safe and highly effective probiotic candidates.

Keywords

• Lactic acid bacteria (LAB)
• Probiotics
• Antibiotic sensitivity
• Antimicrobial metabolites