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摘 要：本实验从酸奶和酸奶发酵剂中分离筛选出三种菌株R1，R2和R3，根据菌落形态特征、革兰氏染色实验、镜检实验以及发酵实验进行初步鉴定；绘制三种乳酸菌的生长曲线，通过定时测定相同条件下单菌发酵实验过程中三种乳酸菌的pH值及滴定酸度来考察三种乳酸菌的产酸性能及后酸化能力；通过标准曲线法比较发酵前后蛋白质含量的变化。经初步鉴定三种菌株均为乳酸菌；相同条件下对这三种乳酸菌发酵过程中产酸性能的比较分析表明R3的产酸速率大于R2，R1的产酸速率最慢；对后酸化能力的比较分析表明R1的后酸化能力最强，R3的后酸化能力最弱。
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关键词：筛选；乳酸菌；产酸性能；后酸化能力
Acid Producing Characteristics of Several Different Lactic Acid Bacteria Strains
Abstract: In this experiment,we isolated three kinds of lactic acid bacteria R1,R2 and R3 from yogurt and yogurt starter, according to the characters of colony morphology, gram's stain experiments, Microscopy laboratory and preliminary identification of fermentation experiment; it could be drawn three kinds of lactic acid bacteria growth curve, Through measuring the pH value and titratable acidity at fixed time of three kinds of lactic acid bacteria which were fermented in the same experimental condition, we could find out the performance of producing acid of each bacteria and the ability of post-acidification It could be compared the changes of protein content before and after fermentation by the method of standard curve
Three types of bacteria were identified to be lactic acid bacteria via preliminary appraisal In the fermentation process of three kinds of lactic acid bacteria which were cultivating under the same condition, the fermentation rate of R3 was faster than R2 and R1 was the slowest As to the post-acidification capability, the comparative analysis shows that R1 is the strongest while R3 was resulted to be the weakest
Key words: Screening; Identification; Lactic acid bacteria; Acid producing; Post-acidification ability
目 录
摘要1
Abstract1
引言 2
1 材料与仪器 2
11 样品来源 2
12 培养基 2
13 主要试剂 2
14 主要仪器和设备 3
2 实验方法 3
21 乳酸菌的初筛及鉴定 3
211 乳酸菌的筛选 3
212 乳酸菌的鉴定 4
22 乳酸菌的扩大培养 4
23 三种乳酸菌生长曲线的绘制 4
24 标准曲线的制备 4
25 酸奶的发酵 5
26 pH-t曲线的绘制 5
27 滴定酸度的测定 5
28 发酵前后蛋白含量的测定 5
3 结果与分析 6
31 乳酸菌的初筛 6
32 乳酸菌的鉴定 6
33 标准曲线 7
34 生长曲线的绘制 7
35 三株乳酸菌酸奶发酵的比较 8
36 三株乳酸菌发酵过程中pH值变化 8
37 三株乳酸菌发酵过程中滴定酸度的比较分析 9
38 酸奶发酵前后蛋白含量的变化 10
4 结论 11
参考文献 11
致谢 13,3688
引言
乳酸菌是一群能从可发酵碳水化合物中产生大量乳酸的革兰氏阳性细菌的通称[1,2]，是一种益生菌。大量研究表明，乳酸菌能增强消化吸收能力、加强胃肠蠕动和机体的物质代谢、帮助人体排泄有毒物质，具有抑制肠道病原菌生长，控制内毒素，抑制肠道内腐败菌生长繁殖和腐败产物的产生，制造营养物质，刺激组织发育，降低血清胆固醇，增强机体免疫力和抗肿瘤等作用[3]。也是乳制品、泡菜等发酵食品中应用最广泛的细菌之一。