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Autoaggregation behavior of bifidobacteria as affected by media composition and incubation tempertures |
O. A. HASSAN1, S. A. Ibrahim2, C. W. Seo2, and A. Shahbazi3. (1) Food Science and Nutrition, North Carolina A&T State University, Greensboro, NC 27411-1064, (2) Dept. of Human Environment & Family Sciences, North Carolina A&T State Univ., Food Microbiology & Safety Lab., 171-B Carver Hall, Greensboro, NC 27411-1064, (3) Dept. of Agricultural & Biosystems Engineering, North Carolina A&T State Univ., Greensboro, NC 27411-1064 The use of bifidobacteria as dietary adjuncts or as a probiotic is a subject of intense and growing interest. Several reports have indicated that bifidobacteria have the ability to provide several health benefits. However, in order for these bacteria to manifest beneficial effects, they need to achieve an essential mass through aggregation. Consequently, the ability of bifidobacteria to aggregate is a desirable property sought for use in commercial food preparations. The objective of this research was to determine the effect of media composition and incubation temperatures on autoaggregation behavior of bifidobacteria. Thirty-seven strains were cultured in Tryptone peptone yeast extract broth (TPY) in anaerobic jars at 37ºC for 18 hours. Autoaggregation behavior of bifidobacteria was determined using different media (TPY, Wilkins-Chalgren and MRS) and incubation temperatures (34, 37, 42° C). Autoaggregation ability was measured as autoaggregation percentage. In this procedure, overnight culture was shaken at different times (30, 60, 90, 120, 150 min). After shaking, 2 ml of the upper suspension of the culture was transferred to anther tube and the optical density (O.D.600 nm) was measured. Three types of autoaggregation behavior characterized the strains: (1) autoaggregation sensitive (S) for strains that formed a precipitate resulting in a clear solution, (2) autoaggregation resistant (R) for strains that produced consistent turbidity, and (3) autoaggregation moderate (M) for strains that showed slight turbidity. Results on the media composition showed that TPY broth increased the autoaggregation behavior of the tested strains, whereas Wilkins-Chalgren and MRS reduced autoaggregation behavior. Calcium ions induced the autoaggregation whereas Tween 20 and Tween 80 reduced autoaggregation behavior. Higher incubation temperature (42° C compared to 34 °C) increased the ability of strains to autoaggregate. Our data indicated that media selection, incubation temperature, calcium ions and addition of Tween are important factors affecting autoaggregation behavior of bifidobacteria. Autoaggregation should be considered when selection of bifidobacteria for their specific use in commercial preparations.
Session 41, Dairy Foods: Dairy microbiology
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