【作者】 刘桂芳；

【导师】 张和平；

【作者基本信息】 内蒙古农业大学 ， 农产品加工及贮藏工程， 2004， 硕士

【摘要】 本课题对来源于蒙古共和国和内蒙古锡林郭勒盟牧民家酸马奶酒样品中分离鉴定得到的6株嗜酸乳杆菌和5株干酪乳杆菌的?－半乳糖苷酶活性、蛋白水解活性及其在发酵乳中的部分生物学特性进行了初步研究，主要研究结果如下：嗜酸乳杆菌和干酪乳杆菌在液体MRS培养基中37℃，18小时培养后均表现出不同程度的?－半乳糖苷酶活力，嗜酸乳杆菌的的乳糖酶活力单位为0.767~5.602u，平均酶活2.217u，干酪乳杆菌的乳糖酶活力单位为0.211~3.312u，平均酶活1.070u。菌种之间有差异，菌株之间也存在差异。嗜酸乳杆菌和干酪乳杆菌具有一定的蛋白水解活性，pH、温度、反应时间都会对其蛋白水解活力产生影响。不同菌株蛋白水解作用的最适pH有所不同。在本实验温度范围内，温度升高有利于蛋白水解。嗜酸乳杆菌和干酪乳杆菌发酵乳及其冷藏保存的研究表明，在37℃发酵过程中，嗜酸乳杆菌和干酪乳杆菌的产酸量平稳上升，发酵乳中游离氨基酸的量有不同程度的增加。24小时发酵结束后，嗜酸乳杆菌发酵乳平均酸度为115.5゜T，pH值变化在3.71~4.47之间，乳中酪氨酸含量为95.7ug/ml~135.15ug/ml；干酪乳杆菌发酵乳平均酸度为99.36゜T，pH值变化在3.86~4.83之间，乳中酪氨酸含量为94.8ug/ml~130.05ug/ml，供试菌株全部凝乳并有程度不同的芳香气味。在4℃冷藏保存的过程中，嗜酸乳杆菌和干酪乳杆菌保持了一部分蛋白水解活力，发酵乳中游离氨基酸的量继续增加。随着发酵乳pH的降低，供试菌株的?－半乳糖苷酶活性下降，宏观表现为产酸量继续增加，但变化趋于平缓。且在发酵乳保存到21天时，嗜酸乳杆菌和干酪乳杆菌具有较高的存活率，活菌数均高于108cfu/ml。更多还原

【Abstract】 The subject of present research is ?-galactosidase, proteolytic activities and some biological characteristics of them in yoghurt of six strains of Lactobacillus acidophilus and five strains of Lactobacillus casei.Strains were isolated from the koumiss samples collected from the heardsman,s house in Mongolia and Inner Mongolia – Xilingole District .The ?-galactosidase activities of Lactobacillus acidophilus and Lactobacillus casei were different. The activity range of ?-galactosidase was 0.767u~5.602u, and the average activity is 2.217u for the former. The range activity of ?-galactosidase was 0.211u~3.312u, and the average activity was 1.070u for the latter. Proteolytic activities varied among strains of L.acidophilus and L.casei .Temperature , pH , and reaction time affected the proteolytic activities. The maximal proteolytic activities of individual strains were different .With the increasing of the temperature the proteolytic activities of both strains were rising in this reseach. Some biological characteristics of the both cultures incubated in skimed milk at 37℃for 24 hours and then stored at 4 ℃for 21 days were studied . During the fermentation at 37℃ for 24 hours ,a significant increasing of acid production and soluble trysine in yoghurt were detected . At the end of fermentation , the average titration acidity of yoghurt inoculated L.acidophilus and L.casei were 115.5゜T and 99.36゜T respectively, correspondingly pH varied among 3.71~4.47 and 3.86~4.83 .The concentration range of soluble trysine was 95.70ug/ml ~ 135.15mg/ml for the former,and 94.80 ug/ml ~ 130.05 mg/ml for the latter. Some of ?-galactosidase and proteolytic activities of both strains were maintained during the observation stored at 4℃ for 21 days .L.acidophilus and L.casei both kept relatively high viability (>108cfu/ml) until the 21th day.更多还原