99D-21 |
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S. Y. Kim, K. I. Jang, H. J. Kwon, and K. Y. KIM. Department of Food Science and Technology, Chungbuk National University, 48 Gaeshin-dong, Heungduk-gu, Cheong-ju, 361-763, South Korea Antimicrobial activities of probiotic LAB strains against pathogenic bacteria such as Escherichia coli, Salmonella spp. and others, are important for the maintenance of the normal intestinal microflora. The inhibition by LAB could be due to the production of inhibitory compounds such as organic acids, hydrogen peroxide, and antibacterial substances, or to the competition with pathogens on adherence to the intestinal epithelial cells. Due to their beneficial roles in gastrointestinal tract, probiotic strains have been proposed to offer therapeutic advantages The objective of this study was to isolate and identify lactic acid bacteria (LAB) exhibiting beneficial (probiotic) properties in vitro. A total of 112 lactic acid bacterial strains tentatively identified as Streptococcus, Lactobacillus, and Bifidobacterium on the basis of bacterial characteristics, were isolated from feces of five healthy breast-fed (BF) infant volunteers selected before weaning. Of the number of bacteria isolated, fifty were acid-tolerant when tested in MRS broth adjusted to pH 2.0 (for Lactobacillus and Streptococcus) and pH 2.8 (for Bifidobacterium) and also highly resistant to bile salts at 0.3% (w/v) Oxgall. The isolates were further tested for both their cholesterol-lowering abilities using MRS supplemented with 0.5% (w/v) taurodeoxycholic acid (TDCA) and 0.037% (w/v) CaCl2, and antimicrobial activities against E. coli O157:H7, E. coli KCTC 1467, Salmonella enteritidis KCCM 12021, and Staphylococcus aureus KCTC 1916. Furthermore, in vitro adherence to Caco-2 cells was assessed for fifteen of the isolates that emerged with the best cholesterol-lowering and antimicrobial profiles. Six of these isolates finally were identified using a microbial rapid identification system (MIDI, HP Inc., USA). This study has reported on the beneficial (probiotic) properties of LAB from breast-fed infants using in vitro tests that took into consideration the chemical compositions of gastrointestinal environment. In vivo experiments would be needed in the future to confirm these observations.
Session 99D, Food Microbiology: General
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