Isolation, identification and probiotic potential of lactic acid bacteria and yeasts from commercial yogurt and homemade non-dairy fermented food “KANJI”

Abstract

South Asian cuisines encompasses a rich variety of traditional fermented foods, which hold great promise as sources of probiotic bacteria with notable health benefits. This study aimed to isolate and characterize probiotic strains from homemade plant-based fermented foods (kanji drink and rice kanji) and commercial dairy-based probiotics (sweetened and probiotic yogurt). The samples were found safe for consumption, devoid of indicator microorganisms and hemolytic activity. They exhibited a diverse microflora with substantial microbial counts (>106 CFU/ml), identified as yeasts and lactic acid bacteria (LAB) namely Lactobacillus curvatus, Leuconostoc mesenteroids, Lactobacillus delbrueckii ssp lactis, Lactobacillus plantarum, and Lactobacillus delbrueckii. Antimicrobial activity tests against six foodborne pathogens demonstrated significant reductions in their growth, highlighting the broad-spectrum antimicrobial potential of the probiotic isolates against gram-positive and gram-negative bacteria. The mixed consortium of samples showed higher growth inhibition compared to individual isolates, emphasizing the importance of microbial diversity in probiotic formulations. The samples' mix consortiums also displayed high auto-aggregative (42.36%–75%) and co-aggregative abilities (up to 93%) with the pathogens over time, with sweetened yogurt showing the highest co-aggregation percentage. The antimicrobial activity of the mix consortiums correlated positively with auto-aggregative capability but negatively with co-aggregative capability, although these correlations were not statistically significant. Consumer acceptance tests, using a nine-point hedonic scaling, favored commercial yogurts over homemade kanji, with sweetened yogurt receiving the highest scores. In conclusion, this study provides insights into the safety, quality, microbial characteristics, antimicrobial activity, aggregative capability, and consumer acceptance of both commercial yogurt and homemade kanji. Considering the limitations of dairy-based probiotics and the growing popularity of vegetarian diets, promoting the consumption of homemade plant-based fermented foods like kanji, which offer wholesome nutrition and potential probiotic benefits, is recommended. Future research should focus on characterizing the in-vivo probiotic potential and standardizing formulations based on consumer demands.