41-10 |
Screening and selection of acid and bile resistant Lactobacillus reuteri |
S. A. AHMAD1, C. W. Seo1, A. Shahbazi2, and S. A. Ibrahim3. (1) Dept. of Human Environment & Family Sciences, North Carolina A&T State Univ., Food Science & Nutrition, 171-B Carver Hall, Greensboro, NC 27411-1064, (2) Dept. of Agricultural & Biosystems Engineering, North Carolina A&T State Univ., Greensboro, NC 27411-1064, (3) Food Science and Nutrition, North Carolina A&T State University, 171-B Carver Hall, Greensboro, NC 27411-1064 Probiotic supplements are becoming increasingly popular in the United States and Europe. Although there are many different types of probiotics, the most common live cultures that found in yogurt products are L. bulgaricus, S. thermophilus, L. acidophilus , and bifidobacteria. In addition to these beneficial cultures, some dairy industries are beginning to add Lactobacillus reuteri to their products as beneficial culture. L. reuteri helps prevent and treat both viral and bacterial diarrhea enhancing the body’s resistance to gastrointestinal disease. However, in order to survive and colonize in the gastrointestinal tract, L. reuteri should express high tolerance to acid and bile salt. The purpose of this work was to investigate the effect of acid and bile salt on the survival and growth of L. reuteri that are considered for use as dietary additives in food industry. Five strains (CF 2F, DSM 20016, MM 7, MM 2-3, and SD 2112) of L. reuteri were used in this study. Overnight cultures were inoculated into fresh MRS broth with various concentrations of bile salt (0.0, 0.1, 0.2, 0.3, 0.4%) and pH values (pH 2.0, 3.0 and 6.5). Samples were then mixed well and incubated at 37 ° C for 48 hrs. Bacterial growth was monitored by measuring turbidity at 610 nm in a spectrophotometer at different time intervals during the incubation period. Results showed that bile salt at 0.3% caused a significant reduction in the growth of all tested strains (P< 0.05). The survival of L. reuteri differed significantly among tested strains; MM 2-3 showed significantly higher growth rates than the other tested strains over the 48 hr incubation period. At bile salt concentration of 0.2% significant growth reduction (P <0.01) was observed for strains CF2 F and MM7. None of the tested strains seemed to survive low pH (2.00 and 3.00). Selection of acid and bile tolerance are important characteristics for the use of L. reuteri cultures as a dietary additive.
Session 41, Dairy Foods: Dairy microbiology
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