Clinical microbiologyCharacterization of Lactobacillus isolated from dairy samples for probiotic properties
Introduction
Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host [1]. Most probiotic microorganism belongs to the lactic acid bacteria (LAB) viz. Lactobacillus spp., Enterococcus spp. and Bifidobacterium [2]. Most of the species of the genus Lactobacillus are part of human and animal commensal intestinal flora [3] and consists of a physiologically and genetically diverse group of rod-shaped, Gram-positive, non-pigmented, non-spore forming [4], catalase negative, microaerophilic to anaerobic LAB [5] with widespread use in fermented food production [6]. These microorganisms are also called friendly bacteria and are generally recognized as safe (GRAS) microorganisms [7]. The lactobacilli isolated from dairy products have long history of safe use [1] and are widely used as starter cultures in the food industry viz. fermented milk, alcoholic beverages, sourdough and silage preparation [8]. Several health benefits associated with the consumption of probiotic bacteria include; controlling intestinal infections, improving lactose utilization, lowering blood ammonia level [9], [10], influencing immune system and low serum cholesterol level [11], [12]. There is an increase in use of probiotic bacteria in variety of food products viz. yoghurt, cheese, drinks and dietary supplements based on their therapeutic benefits [13]. Keeping in view the importance of probiotics, the present study is endeavored to screen twelve previously reported Lactobacillus isolates (8 from household curd and 4 from household milk) [14] for the probiotic properties viz. resistance against bile salt, acid pH values, antibiotics, pathogenic microbe inhibition and select a potential isolate for further investigation.
Section snippets
Bacterial strains
Thirty dairy samples (household milk and curd) were collected from local area of Solan, H.P., India. Serial dilutions of 1 ml dairy samples were prepared in peptone water and then 100 μl sample from different dilutions were spread over the solidified MRS (de Man, Rogosa and Sharpe) medium (HiMedia, India) and incubated at 37 °C for 24–48 h under anaerobic conditions for the isolation of Lactobacillus. Pure cultures of isolated colonies were obtained after re-streaking on MRS agar plate. Each
Results
Thirty bacterial isolates were initially obtained from thirty dairy samples collected from Solan district in Himachal Pradesh, India. Out of thirty, 14 isolates were from milk sample and 16 isolates were from curd samples. Characterization of isolates was performed on the basis of their morphological characteristics viz., type of colony, color, margin, elevation, opacity and presence of pigment and Lactobacillus specific biochemical tests. Based on morphological, cultural and biochemical
Discussion
In the present study twelve Lactobacillus spp. isolated from dairy samples were characterized for probiotic properties and results were compared with the existing literature. In screening study eight, out of twelve isolates were bile resistant and Lactobacillus isolates showing resistance ≥50% at 0.3% (w/v) bile salt were considered as bile resistance strains [16]. Highest resistance (72.36% and 68.62%) was observed with isolate LBS 2 at 0.3% and 0.45% of bile salt respectively. Gilliland [26]
Conclusion
In conclusion one potential probiotic isolate LBS 2 was obtained after screening of twelve Lactobacillus isolates for the probiotic properties. This isolate LBS 2 from the household curd sample of Solan, district of Himachal Pradesh was identified as L. rhamnosus LBS 2 after phenotypic and genotypic characterization. High resistance to bile salt, tolerance to acid pH values, broad spectrum microbial pathogen inhibition and adherence to epithelial cells seems to be a potential advantage of this
Acknowledgments
The authors are thankful to Dr. Rohit Goyal, Faculty of Pharmaceutical Sciences, Shoolini University, Solan, India for his help in epithelial cells adherence assay and Er. Sandeep, Indian Institute of Technology, Mandi, India for SEM analysis in the present study.
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