Vol. 11, Special Issue 7 (2022)

Author(s):
Malashree and Akshaykumar

Abstract:
Probiotics are live microorganisms which when consumed in large number together with a food promote the health of the consumer. The aim of this study was to evaluate in vitro probiotic properties of lactic acid bacteria (LAB) isolated from Human feces and dairy products such as raw milk and dahi samples. A total of 40 isolates were selected from the samples. These isolates of Human origin (H1 –H20) and dairy origin (D1-D20) were initially screened as Gram-positive, rods, catalase-negative isolates. Human isolates H4, H8, H9, H10, H14 and D6, D7, D9, D12, D13 confirmed the Lactobacillus genus identification. Further these 10 isolates were subjected for in vitro probiotic properties. Isolate H9 and D12 were able to survive at pH 3.0 for 120 min as indicated by log counts up to 5.01 to 5.2, whereas D9 showed low viability at pH 2.0 at 120 min. For bile tolerance study isolate H9, H10, D12 and D13 were able to tolerate 1% bile for 3 hrs with a log count varying from 6 to 6.3 whereas D9 was found to be bile sensitive with log count of 2.8. Almost all the isolates were moderately or highly sensitive towards all the antibiotics used in this study, except ofloxacin. All the isolates were resistant to vancomycin except H9 and D9. Maximum cell surface hydrophobicity was observed for D9 (52%) while it was minimum for H9 (4%). In case of antibacterial activity against pathogenic bacteria, majority of the isolates showed inhibition against S. aureus and E. coli (73%) followed by B. cereus and S. dysenteriae (70%) and S. typhi (33%). Only 3 out of 10 isolates namely H4, H9 and D7 exhibited a moderate level of BSH activity (++) as indicated by the dense precipitation of the sodium taurodeoxycholate. Among 10 isolates 4 (H4, H8, H9, H14) were identified as Lactobacillus plantarum with the amplification of 248 bp product using primer L pla 3/ L pla 2.The sequence analysis showed that D6, D7, D9, D12, and D13 belonged to Lactobacillus rhamnosus, whereas H10 as L. plantarum. Studies revealed that the Lactobacillus plantarum and Lactobacillus rhamnosus strains were found to be potentially useful to produce probiotic products.