| Summary: | 碩士 === 中國醫藥大學 === 營養學系碩士班 === 95 === This study investigated the changes in probiotic properties of lactic acid bacteria (LAB) after being treated with simulate gastrointestinal condition of acid and bile salts. Lactobacillus acidophilus BCRC 10695, Bifidobacterium bifidum BCRC 14615, L. paracasei BCRC 14023 were used as probiotics, and Clostridium perfringens BCRC 13019 was studied in the antagonistic activity for the selected LAB. Tested items included acid and bile tolerance, adherence, antagonistic activity, β-galactosidase activity, and safety aspect of the LAB after acid and bile treatment. For the acid and bile tolerance tests, the LAB were treated with pH 2, 3, 4 acid solution and 0.1, 0.2, 0.3% oxgall bile solution, respectively or continually. The adhesion assay determined the adherence rate of LAB adhered to the simulate intestinal Caco-2 cell as the tested model. Both adherence inhibition and displacement test were used for the study of LAB antagonistic activity against C. perfringens. Results showed that L. acidophilus exhibited the best acid tolerance (p＜0.05), and L. paracasei had better bile resistance than the other two tested probiotics (p＜0.05). All tested LAB had better viable count and survival rate after being treated with pH 4 acid solution and then 0.1% bile soluion. Adhesive ability of LAB after exposure to acid (pH 4) and bile (0.1%), shown in adherence rate in descending order, were L. paracasei (80.6%)＞L. acidophilus (9.71%)＞B. bifidum (5.20%). LAB pretreated with pH 4 acid solution and 0.1% bile solution retained the ability of diminishing the adhesion of C. perfringens (p＜0.05). After exposure to the same pH acid solution, the injury of LAB cell membrane raised with the increased bile salt content, leading to higher β-galactosidase values. The result of invasion test for safety aspect revealed that LAB possessed a safety property. Some of the tested LAB after the treatments of acid solution with low pH value plus bile solution of high concentration would lead to death. The tested LAB surviving the treatment of pH 4 acid and 0.1% bile solution still remained the characteristics of adhesiveness and antagonistic activity toward the pathogen.
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