Evaluation of the Probiotic Potential of Lactobacillus acidophilus Strain JB2CON

Probiotics have attracted much attention recently because of their potential health benefits and aim at correcting the imbalance of gut microbiota. Dairy fermented foods play an important role as a probiotic carrier, and fermented dairy products like dahi are well known for their ability to maintain the viability of bacteria and their acceptance by consumers. Nevertheless, the production of low-cost, locally manufactured probiotic products that possess antimicrobial activity against food pathogens is relatively scarce. The principal goal of this current study was to isolate a new potential probiotic strain to prepare contamination-free probiotic dahi in a dosage form with a desired shelf life.

To achieve our target, firstly, probiotic dahi was prepared by a probiotic strain, Lactobacillus acidophilus JB2CON (OM909067) (identified by 16S sequencing) isolated from natural dahi in Dhaka, Bangladesh. Probiotic potential was assessed by transmission electron microscopy, acid and bile tolerance, hemolytic activity, antibiotic sensitivity, and antagonistic activity against pathogens, while sensory acceptance of the probiotic dahi was evaluated by 16 participants using a 9-point hedonic scale.

The isolate exhibited five probiotic features by in vitro test and had an antagonistic effect against four different bacterial pathogens and Candida albicans. More interestingly, it inhibited Escherichia coli (diameter of zone of inhibition = 15.75 ± 0.35) the most. In the time-kill analysis method, E. coli was killed within 5.50 h of fermentation. In the antibiotic sensitivity test, the isolated bacterial species exhibited clear inhibition, with ampicillin producing the largest zone (69.33 ± 11.06 mm), followed by tylosin (67.33 ± 6.43 mm). In the acid tolerance test, the probiotic count decreased by ~3.3 log units after 24 h, while bile salt exposure (0.025% and 0.5% oxgall) reduced viable counts in a concentration-dependent manner. The probiotic dahi prepared in this study was rated as "moderately liked" by 16 participants using a 9-point hedonic scale. Stability testing identified 14 days as the optimal shelf life, with increased probiotic counts and no adverse effect of minor pH changes on dahi taste.

The most significant impact of this research is that the probiotic dahi of our experiment might be used as a cheap option for preventing pathogenic E. coli-related foodborne diseases worldwide, especially in underdeveloped countries like Bangladesh.