Bile salt hydrolase and antimicrobial activities of three bile resistant probiotics Lactobacillus plantarum strains isolated from Cameroonian artisanal fermented milk

Probiotics are well known for their efficacy as dietary adjuncts providing benefits to consumers. However, the selection of probiotics before incorporation into diet requires the scrutiny of a well-defined set of criteria. Hence, three Lactobacillus plantarum strains (GGU, GLA51 and GLP56, having KU949009, KU949010 and KU949011 respectively as GenBank accession numbers) previously isolated from Cameroonian traditional fermented milk have been used in this study for the evaluation of their Bile salt hydrolase and antimicrobial activities. Bile tolerance test was carried out by monitoring the bacterial growth at different Oxgall bile concentration (0.3%, 0.5% and 1%). The bile salt hydrolase activity was measured by determining the amount of amino acid liberated from conjugated bile salts by lactobacilli strains. Also, three bshgenes (bsh1 gene specific to Lactobacillus plantarum species, bshA and bshB genes specific to Lactobacillus acidophilus species) involved in the bile salt hydrolase activity were screened. The antimicrobial activity of the strains was evaluated using the agar-spot test. The three Lactobacillus plantarum strains showed survival percentages higher than 90% in the presence of 0.3% of Oxgall bile, and the delays of growth ranged from 0 to 10 min. Their bile salt hydrolase activity ranged from 15.62 ± 3.00 to 23.91 ± 5.82 U/mg towards Oxgall and from 10.47 ± 2.76 to 24.57 ± 6.31 U/mg towards Taurodeoxycholate. Only Lactobacillus plantarum GLA51 was found to harbor thebsh1 gene. Its sequence was deposited in the Genbank under the accession number MF098542. The analysis of thisbsh1 gene sequence from L. plantarum GLA51 indicated that it contained an open reading frame (ORF) of 838 nucleotides encoding a 278 amino acids protein. The three Lactobacilli strains showed inhibitory activity against the pathogenic or spoilage bacteria tested, except for Shigella flexneri. These results suggest that the three Lactobacillus plantarum strain show potential for probiotic applications.Keywords: Bile salt hydrolase activity, antimicrobial activity, Lactobacillus plantarum, bile tolerance