| Summary: | 碩士 === 國立臺灣師範大學 === 生物研究所 === 91 === The health-promoting effects of Lactobacilli include maintenance of a normal intestinal microbiota, increased nutritional value of foods, anticarcinogenic activity, reduction of serum cholesterol levels, alleviation of lactose intolerance and stimulator of the immune system.
The studies was isolation of the Lactic acid bacteria from commercial milk products. 4 strains of Lactobacilli were screened and selected from samples. 3 strains of Lactobacilli were identified as Lactobacillus paracasei subsp. paracasei、Lactobacillus casei subsp. rhamnosus and Lactobacillus halotolerans, the other strain which was labeled L2-2 was not. The rate of growth by 4 Lactobacilli strains depended on the number of cells in the initial inoculum but not influence of the final number of cells.
Among four types of medium tested including MRS, milk, soy bean water and loofah water, four strain of Lactobacilli grew best in milk medium. Besides, the result showed that four strains tested in four different medium reached stationary phase in 24 hours.
The formation of B-vitamins（niacin, vitamin B1, vitamin B6 and vitamin B12）during the fermentation of MRS broth was investigated. The results showed that vitamin B1,vitamin B6 and vitamin B12 were produced by 4 Lactobacilli strains, but they could not synthesized niacin.The formation of vitamin B12 by Lactobacillus spp.L2-2 was
higher than the others, and its concentration was 0.27217 ng/mL. The formation of vitamin B6 by Lactobacillus halotolerans was higher than the others, and its concentration was 5.088 ng/mL. The formation of vitamin B1 by Lactobacillus paracasei subsp. paracasei was higher than the others, and its concentration was 0.506 mg/mL. The addition of cobalt chloride resulted in an increase in vitamin B12 formation by four strains, but there were no significant different.
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