Probiotic Potential Of Lactic Acid Bacteria Isolated From Selected Traditionally Fermented Beverages

Abstract

Probiotics are live microorganisms which when administered in adequate amount confer a health benefit to the host. Fermented foods are the major sources of Probiotics. Keribo, Bukuri and Korefe are among the common traditional fermented foods consumed in different parts of Ethiopia. However, the probiotic potentials of these foods were not documented although few studies were made on their microbiology. Therefore, the aim of this study was to evaluate the probiotic potential of LAB isolated from such products under laboratory condition. Samples from these three traditionally fermented food products were prepared following traditional preparation procedures as described earlier and used in the current study. The Lactic acid bacteria found in each fermented food products were isolated and characterized using standard morphological and biochemical tests. The In vitro probiotic potential was conducted simulating the GIT condition (tolerance to stomach PHand Gastric enzymes, antimicrobial activities against pathogens). The antimicrobial activities of LAB isolates against Salmonella spps, Pseudomonas aeruginosa, Staphylococcus aureus and E. coli were determined following the standard Agar well Diffusion method. A total of 52 LAB isolates (14 from Keribo, 23 from Bukuri and 15 from Korefe) were screened. The result indicated that all the presumptive LAB isolates were gram positive, Catalase negative, none motile, none spore forming and lactic acid producers. Strains of Leuconostoc spp. were found dominating Keribo samples. Likewise, homo fermentative Lactobacillus strains were dominant in Bukuri samples. But, both the hetero fermentative and the homo fermentative LAB strains were encountered in almost equal proportion in Korefe sample. Analysis on the in vitro probiotic potential indicated that 38.5% (20/52) isolates were tolerant to stomach pH. The 20 isolates were almost equally distributed over the sample sources (7 isolates from Keribo, 6 from Bukuri and 7 from Korefe). One isolates each of the Korefe (Kr2) and Bukuri (Bk10) exhibited the highest antimicrobial activity against Salmonella spps with inhibition zone diameter of 19.5  3.6 and 16  2.8 mm, respectively. Likewise, Ke1 from Keribo, Bk1 from Bukuri and Kr9 from Korefe exhibited the highest inhibitory effect against E. coli with inhibition zone diameter of 17.5  3.8, 16.5  2.2, 13 1.4 mm, respectively. In addition, Kr11 from Korefe and Bk2 from Bukuri exhibited the highest inhibitory activity against Staphylococcusaureus with inhibition zone, 22  2.8 and 17  4.2 mm, respectively. ix Moreover, Kr1 from Korefe, Bk1 from Bukuri and Ke1 from Keribo exhibited the highest inhibitory activity against Pseudomonas aeruginosa with inhibition zone, 20.5  3.7, 17.5  2.8, 10.5 2.9mm, respectively. Over all, most of the isolated LAB showed remarkable antibacterial activities both against gram positive and gram negative pathogens although the spectrum of inhibition was different for the different isolates. In conclusion, the results of the study indicated that, the 20 isolates screened from the three traditional fermented food products had promising probiotic characteristics making Keribo, Bukuri and Korefe candidate probiotic foods for further in depth evaluation of the isolates at molecular level with some more screening criteria included in the probiotic evaluation. (Bk1, Bk2, Bk10, Kr11 represent Lactobacillus strains, Ke1, Ke5 are Pediococcus species while Ke8, Kr9 are strains of the genus Leuconostoc).