目前許多研究指出乳酸桿菌可維持腸道內微生物正常之平衡、增加食品的營養價值、抑制癌症、降低血中膽固醇、改善乳糖不耐症及刺激免疫系統等特性。
本研究是由市售的乳酸製品分離且純化出乳酸菌，並篩選出乳酸桿菌之菌株，共有4株，菌種鑒定分別為Lactobacillus paracasei subsp.paracasei、Lactobacillus casei subsp.rhamnosus、Lactobacillus halotolerans、另外一株種名尚未鑑定出，給予編號Lactobacillus spp.L2-2。研究主要探討各乳酸桿菌之生長情形，並且觀察在不同的培養基中，乳酸桿菌的生長情形有何不同，結果顯示開始接種的菌數量會影響生長速度，並不影響最終的菌數量；且該4株菌在牛奶培養基生長最好，其次為MRS broth、黃豆水和絲瓜水培養基。此外，生長測定在在四種培養基下，是以24小時達到穩定期。菌株在MRS broth下，微生物檢驗分析來定量乳酸桿菌產生維生素B12、維生素B6、維生素B1及niacin的能力，該4株菌均能產生維生素B12、維生素B6與維生素B1，其中Lactobacillus spp.L2-2所產生的維生素B12的含量較其他三者為高，其含量為0.27217ng/mL；在產生維生素B6的含量以Lactobacillus halotolerans為最高，其含量為5.088 ng/mL；在產生維生素B1的含量以Lactobacillus paracasei subsp.paracasei為最高，其含量為0.506 mg/mL。另外，該四株菌皆無法產生niacin。在培養液中添加二價金屬離子（氯化鈷）能促進該四株菌合成維生素B12的量，但並無顯著性的差異。

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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