Molecular characterization and 16S rRNA sequence analysis of probiotic lactobacillus acidophilus isolated from indigenous Dahi (Yoghurt)

摘要

Indigenous yoghurt is being the most popular fermented milk product in Pakistan, produced by heterogenous lactic acid bacteria (LAB). Nowadays LAB has drawn particular interest in food and nutrition science because of functional and probiotic attributes. Among various genera of LAB, Lactobacillus acidophilus is considered to be a potential candidate. Present study was designed by keeping in view the probiotic attributes of L. acidophilus. Isolation was conducted on MRS media supplemented with 0.7% bile salts to screen out bile tolerant isolates. Out of sixty lactobacilli, eighteen were identified as L. acidophilus by performing gram staining, catalase, carbohydrate fermentation test and growth at different temperatures. Only six had shown tolerance of pH 2 up to 50% and only three had shown a wide range of antimicrobial activity against tested organisms. S. epidermis found to be more sensitive with a maximum zone of inhibition (18 mm) and A. baumanii and S. aureus were least sensitive with a smallest zone of inhibition (11.5 mm and 12 mm respectively). 16S rRNA gene amplification, sequencing and phylogenetic tree construction of the obtained sequences with the most closely related lactobacillus spp. was performed. Sequences are available in GeneBank and NCBI with the accession numbers KU877440 (WFA1), KU877441 (WFA2) and KU877442 (WFA3). Presence of probiotic L. acidophilus in locally fermented product (dahi) has proved its potential along with bile salts supplementation in MRS media is helpful in initial screening of probiotic isolates.