Isolation of a Potential Probiotic Levilactobacillus brevis and Evaluation of Its Exopolysaccharide for Antioxidant and α-Glucosidase Inhibitory Activities.

The probiotic properties of ten lactic acid bacteria and antioxidant and α-glucosidase inhibitory activities of the exopolysaccharide (EPS) of the selected strain were investigated in this study. Levilactobacillus brevis L010 was one of the most active strains across all the in vitro tests. The cell-free supernatant (50 g/l) of L. brevis L010 showed high levels of both α-glucosidase inhibitory activity (98.73 ± 1.32%) and 2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity (32.29 ± 3.86%). The EPS isolated from cell-free supernatant of L. brevis L010 showed 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical-scavenging activity (80.27 ± 2.51%) at 80 g/l, DPPH radical-scavenging activity (38.19 ± 9.61%) at 40 g/l, and ferric reducing antioxidant power (17.35 ± 0.20 mg/l) at 80 g/l. Further, EPS exhibited inhibitory activities against α-glucosidase at different substrate concentrations. Kinetic analysis suggests that the mode of inhibition was competitive, with a kinetic constant of Km = 2.87 ± 0.88 mM and Vmax = 0.39 ± 0.06 µmole/min. It was concluded that the EPS might be one of the plausible candidates for possible antioxidant and α-glucosidase activities of the L. brevis L010 strain.

Isolation of acid tolerant lactic acid bacteria and evaluation of α-glucosidase inhibitory activity.

In this study, lactic acid bacteria strains (LABs) were isolated from Korean traditional fermented food and examined as potential probiotics using in vitro methods. Ten LAB strains survived in de Man, Rogosa and Sharpe broth adjusted to pH 2.5 were tested for resistance to acidic conditions and bile, antimicrobial activity, and α-glucosidase inhibitory activity. Among them, strain MBEL1397 showed antimicrobial activity against Bacillus cereus and exhibited survival rates of over 97% in acidic and bile conditions. The α-glucosidase inhibitory activity was 3.91 ± 0.25%, corresponding to approximately 2.3 times higher than that of acarbose. MBEL1397 was susceptible to ampicillin, erythromycin, and penicillin G and identified as Lactobacillus sakei. It was deposited to Korean Collection for Type Culture (KCTC) as KCTC14037BP. In conclusion, these results demonstrate that L. sakei MBEL1397 might be prominent probiotics with potential hypoglycemic effects.