酸乳中混合乳酸菌的分离及鉴定

Isolation and identification of L.Bulgaricus and S.Thermophilus

利用MRS琼脂培养基和Elliker琼脂培养基分别对保加利亚乳杆菌和嗜热链球菌进行分离。然后,分别挑取疑似菌落进行革兰氏染色,对镜检结果为革兰氏阳性菌,且细菌形状为杆状和球状的菌种进行生物化学鉴定。采用糖发酵试验进行生化鉴定。对保加利亚乳杆菌进行麦芽糖、七叶苷、乳糖、蔗糖和葡萄糖5种糖的发酵试验,而对于嗜热链球菌进行葡萄糖、麦芽糖和蔗糖的发酵试验。而后,对葡萄糖、蔗糖发酵阳性,麦芽糖发酵阴性的菌种进行45℃培养。结论表明:在MRS琼脂培养基上,菌落较大、透明、灰白色,镜检细菌形状为杆状,麦芽糖和七叶苷发酵试验均为阴性,乳糖发酵阳性的菌种,即为保加利亚乳杆菌。在Elliker琼脂培养基上分离出的菌种,镜检细菌形状为球状,葡萄糖、蔗糖发酵呈阳性,麦芽糖发酵阴性且能在45℃条件下生长的菌种即为嗜热链球菌。

In this study, L.Bulgaricus and S. Thermophilus are isolated by the use of MRS and Elliker agar culture medium respectively.The suspicious colonies are treated with Gram staining,and Gram-positive, spherical and rod bacteria are identified biochemically.Maltose and esculoside are used for L.Bulgaricus carbohydrate fermentation ,and glucose is used for S.Thermophilus correspondingly.Then,positive bacteria under glucose fermentation is culture at 45 ℃.To draw conclusions, L.Bulgaricus owned properties of transparent,gray-white,colonies in MRS agar medium,and rod shape under microscopic examination as well as negative results of maltose andesculoside fermentation.nevertheless, S.Ther- mophilus isolated from Elliker arar medium is spherical under microscopic examination,and positive bacteria of glucose fermentation,which could grow at 45 ℃.