Probiotic Properties and Bile Salt Hydrolase Activity of Some Isolated Lactic Acid Bacteria

Document Type : Original Article

Authors

1 Chemistry of Natural & Microbial Products Department, National Research Center, Giza, Egypt

2 Microbiology Department, Faculty of Science, Ain Shams University, Cairo, Egypt

Abstract

EIGHT lactic acid bacterial (LAB) isolates were obtained from food and non-food sources and identified by 16S rRNA gene sequence analysis. Based on the sequencing results, the isolates belong to two species of lactobacilli, Lactobacillus plantarum and L. rhamnosus. These strains were then compared with a reference strain, Lactobacillus casei, to assess various probiotic properties, such as haemolytic activity, histamine formation ability, stress tolerance under certain stress conditions, antibiotic susceptibility and in vitro adhesion ability. Moreover, bile salt hydrolase (BSH) activity was evaluated both qualitatively and quantitatively. The results showed that none of the isolates demonstrated any haemolytic activity or histamine formation. The isolated strains were also tolerant to acidic and alkaline conditions (pH 2.5, 3.5 and 9) for 3 and 6 h, as well as osmotic (3 M NaCl) and heat (55 and 70°C) stress, but were more responsive to oxidative and bile stress. The bacterial isolates also expressed high amounts of BSH, ranging from 90 to 142 U/mg in active cells, compared to L. casei (74 U/mg), which may be useful in cholesterol reduction. All bacterial isolates were resistant to vancomycin and susceptible to amoxicillin, cloxacillin and penicillin. All isolates were also highly hydrophobic (>70%), indicating that they are not easily flushed from the intestines.

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