The study was conducted to evaluate in vitro probiotic properties of lactic acid bacteria (LAB) isolated from fermented Shamita and Kocho. Sixteen samples, 8 each of Shamita and Kocho, were collected from Arat-Kilo and Merkato sites in Addis Ababa, respectively. The average pH values of Shamita and Kocho samples were 3.52 and 3.44, respectively. A total of 140 LAB were isolated, of which 101 isolates (72%) were found to inhibit one or more of the sensitive test organisms Shigella boydii and Salmonella typhimurium but none of them had antimicrobial activity against Staphylococcus aureus. The inhibition diameters on agar medium ranged from 8.5 to 17.5 mm. The 101 isolates having antagonistic effects against the test organisms were evaluated for their bile tolerance. Thirty six isolates (36%) tolerated 0.3% bile salts for 48 h with 55 to 93% survival. The 36 bile tolerant isolates were evaluated for their acid tolerance and 25 (69%), 30 (83%) and 34 (94%) tolerated pH 2, pH 2.5 and pH 3 for 3 h, respectively. Further extension of the incubation period for 6 h reduced the number of isolates to 21 (58%) and 33 (92%) at pH 2 and pH 3. Thirty of the bile tolerant isolates (83%) showed 80 to 94% survival at pH 2.5 for 6 h. These isolates were selected as LAB candidates with probiotic potential. Based on their phenotypic characteristics, the 30 isolates were identified as Lactobacillus (17 isolates), Leuconostoc (6 isolates) and Pediococcus (4 isolates) and Lactococcus (3 isolates). Antibiotic resistance patterns of the 30 isolates showed 100% resistance against oxacillin but lower resistance to levofloxacin; 57% of the isolates were resistant to penicillin. However, all the isolates were sensitive to erythromycin and gentamicin. Multiple drug resistance patterns were observed in two isolates one each from Shamita Lactobacillus (S9) and Kocho Lactobacillus (K64) having multiple resistances to penicillin, levofloxacin and oxacillin. Nine isolates (30%) were selected as probiotic candidates for further test on different fermented foods.
Key words: Lactic acid bacteria; Lactobacillus, Leuconostoc, Pediococcus, Lactococcus spp., acid tolerance, antimicrobial activity, bile tolerance.
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