| Summary: | 碩士 === 國立中興大學 === 畜產學系 === 89 === Lactic acid bacteria and bifidobacteria are widely used for human food. The basic requirements for lactic acid bacteria as probiotics are the capability for tolerance to gastric acid and bile salts, the ability to inhibit pathogenic bacteria, antioxidative activity, and antimutagen activity. In addition, the lactose hydrolysis and synthesis of functional oligo- saccharides of lactic acid bacteria were investigated in order to promote the probiotic value and be used for food. In this study, 35 probiotic strains of lactic acid bacteria and bifidobacteria were screened and selected from infant stool samples, some commercial dairy products, and Food Industry Research and Development Institute in Taiwan.
The results in the hydrolysis and synthesis of saccharides showed that the hydrolysis of lactose changes with variety and ratio of mixed strains. In X treatments (Bifidobacterium, S. thermophilus, L. bulgaricus mixed in 2：2：1), the lactose hydrolysis of X01 and X06 were higher than others, and oligosaccharides synthesis of X14, X04, X08, and X24 were higher than others. In Y treatments (Bifidobacterium, S. thermophilus, L. acidophilus mixed in 2：2：1), the lactose hydrolysis of Y08 was the highest, and oligosaccharides synthesis of Y01 and Y08 were higher than others. In Z treatments (Bifidobacterium, S. thermophilus, L. bulgaricus, L. acidophilus mixed in 1：1：1：1), the lactose hydrolysis of Z02, Z04, Z16, Z21, and Z22 were higher than others. The oligosaccharides synthesis of Z02, Z06, and Z21 were higher than others. The results of TLC showed that all treatments could synthesize oligosaccharides and trisaccharides were the highest. The chemical structures of oligosaccharides were identified by 13C-nuclear magnetic resonance, and the results showed that the oligosaccharides were galactooligo- saccharide which structure was β-galactose-(1→4)-β-galactose-(1→4)-glucose.
Except B. adolescentis CCRC 14609, B. bifidum CCRC 14630 and B. catenulatum CCRC 14667, most lactic acid bacteria and bifidobacteria didn’t have tolerance on pH 2.0 phosphate buffer. And 10 strains have the tolerance on bile salts. According to the acid and bile resistance tests, the selected strains of L. acidophilus CCRC 10695, L. bulgaricus CCRC 10696, L. brevis CCRC 12187, L. rhamnosus CCRC 14029, B. adolescentis CCRC 14607, 14609, L. reuteri CCRC 14625, B.catenulatum CCRC 14667, and B. bifidum CCRC 14670 had 80% viability in imitating digestive tract condition.
All the 30 strains of lactic acid bacteria and bifidobacteria had the inhibition for Bacillus circus, but only L. rhamnosus CCRC 10940, B. longum CCRC 11847, and L. kefir CCRC 14011 had the inhibition for Staphylococcus aureus. There were 18 strains that inhibit Escherichia coli in which B. bifidum CCRC 12585 had the highest efficiency. 26 strains inhibit Samonella typhimurium in which B. breve CCRC 11846 had the highest efficiency. 27 strains inhibit P. fluorescens in which B. breve CCRC 11846 has the highest efficiency.
20 strains of lactic acid bacteria and bifidobacteria were tested for antioxidative activity by the inhibition of linoleic acid oxidation. There were 8 strains have antioxidative activity after incubated for 5 days as measured by the thiocyanate method. Bifidobacterium adolescentis CCRC 14609 has the best antioxidative acitivity. Lactobacillus reuteri CCRC 14625 was the best reducing activity. Commercial lactic acid bacteria B03 had the best scavenging effects on superoxide anion. 7 strains had above 80% scavenging effects on α-diphenyl-2-picryl hydrazyl (DPPH‧) radical. Bifidobacterium bifidum CCRC 14614. Lactobacillus reuteri CCRC 14625 and Bifidobacterium adolescentis CCRC 14609 had more superior chelating effect on Fe2+, which achieve 50%.
In the experiment of antimutagen activity, the results showed that no mutagenicity or toxicity in S. typhimurium TA 98 and TA 100 with any lactic acid bacteria and bifidobacteria strains. B. adolescentis CCRC 14608 had the lowest mutagenicity toward S. typhimurium TA 98 and TA 100. Detected the antimutagen activity of lactic acid bacteria and bifidobacteria on the mutagenicity of S. typhimurium TA 98 and TA 100 induced by NQNO, and which presented light antimutagenity. B. breve CCRC 11846 and B. adolescentis CCRC 14608 had a higher antimutagenic ability for Salmonella typhimurium TA 98. And the percentage of inhibition was over 70%. The inhibition from S. typhimurium TA 100 was higher than from S. typhimurium TA 98. B. adolescentis CCRC 14608, B. bifidum CCRC 14614, and B. adolescentis CCRC 14609 had 85% inhibition rate and B. infantis CCRC 14661 and B. catenulatum CCRC 14667 had 70% inhibition rate.
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