【作者】 吴惠芬；

【导师】 朱伟云；

【作者基本信息】 南京农业大学 ， 动物营养与饲料科学， 2003， 硕士

【摘要】 为了进一步明晰乳酸菌与仔猪健康的关系及其潜在的益生作用，本研究探讨了仔猪断奶前后各肠段中大肠杆菌和乳酸杆菌数量的变化，同时从中分离并鉴定了5株乳酸菌，并对其产乳酸能力、抑菌特性以及在模拟胃肠环境因素条件下的存活进行了研究。整个实验分四部分： 第一部分：哺乳仔猪不同肠段食糜中大肠杆菌和乳酸杆菌数量的比较。试验研究了一窝12头健康仔猪不同日龄、不同肠段食糜中乳酸杆菌和大肠杆菌的数量。结果表明：空、回肠食糜中的大肠杆菌随日龄增加而增加，乳酸杆菌断奶前随日龄增加而增加，断奶后减少；盲、直肠食糜中大肠杆菌和乳酸杆菌数均较为稳定。提示，断奶对仔猪小肠中的微生物数量影响较大，大肠杆菌大量增殖而乳酸杆菌减少，但对仔猪大肠中的微生物数量影响不大。 第二部分：仔猪肠道食糜中乳酸菌和大肠杆菌的分离和鉴定。本试验从仔猪肠道食糜中分离并鉴定获得了五株乳酸菌，分别为L1，多粘芽孢杆菌(B.polymyxa)；L2，干酪乳杆菌(L.casei)；L3，乳球菌(Lactococcus sp.)；L5，芽孢乳杆菌(Sporolactobacillus sp.)和L7，德氏乳杆菌德氏亚种(L.delbrueckii subsp.delbruecki)。同时分离并鉴定了一株大肠杆菌，编号E1。 第三部分：猪源乳酸菌产乳酸能力及抑菌特性的研究。体外厌氧发酵结果表明：L5菌株产乳酸速度最快，pH值下降最快，发酵终末乳酸含量最高，pH值最低。抑菌试验结果表明：5株乳酸菌对大肠杆菌K88、K99、987P、O141、大肠杆菌E1及金黄色葡萄球菌均有不同程度的抑制作用；低pH值条件下抑菌效果显著；排除酸影响后仍有22％～53％抑菌效果；抑菌物质具有热稳定性并对蛋白酶不敏感。 第四部分：模拟胃肠环境因素对猪源乳酸菌存活的影响。本试验研究了模拟胃肠环境因素对L5和L7存活能力的影响，以及L5的耐热特性。结果表明，pH值超过2.5处理150min时，L5的存活基本不受影响，pH1.5时L5能在30min内维持较高的存活率；L7耐酸能力相对较差，只能耐受pH3.5和4.5。L5和L7的生长均受胆盐的抑制，在0.1％胆盐条件下，两菌株4h后存活率分别为21.80％和29.06％；当胆盐浓度高于0.2％时，两菌株4h后存活率不超过0.18％。1％胃蛋白酶对L5、L7的生长繁殖无影响。50℃热处理对L5的存活无影响，80℃以上即显著影响其存活率。更多还原

【Abstract】 To further understand the role of lactic acid bacteria (LAB) in the piglet gut health, spatial and temporal changes of quantity of E. coli and Lactobacillus in the gut of piglets were investigated. Five strains of LAB were isolated and identified from the intestinal contents. The production of lactic acid and antagonistic property of the five LAB strains, and the effect of gastrointestinal factors on the survival of two strains were studied. This thesis includes four sections.In the first section, E. coli and Lactobacillus in the gastrointestinal tract of 12 conventionally raised piglets from the same litter was enumerated. The results showed that the number of Lactobacillus in jejunum and ileum increased as the piglets grew before weaning but decreased after weaning. The number of E. coli in jejunum and ileum increased from suckling into weaning time. There was no apparent change in the number of E. coli and Lactobacillus in caecum and rectum over the time period studied. These results suggested that weaning apparently affected the numbers of E. coli and Lactobacillus in small intestine, with E. coli fast proliferating while Lactobacillus decreasing. Weaning, however, had little effect on the numbers of E. coli and Lactobacillus in large intestine.In the second section, five strains of LAB were isolated from the intestinal contents of piglets. According to the features of Gram staining, and morphological and biochemical characteristics, the five strains, L1, L2, L3, L5 and L7, were preliminarily identified as Bacillus polymyxa, Lactobacillus casei, Lactococcus sp., Sporolactobacillus sp. and L. delbrueckii subsp. delbruecki, respectively. A strain of E. coli was isolated from the same intestinal contents of piglets.In the third section, lactic acid production and antagonistic property of five strains of LAB (L1, L2, L3, L5 and L7) isolated from piglet intestine were investigated. The results showed that among all strains L5 exhibited the most rapid production of lactic acid in the culture, with the highest production value. Accordingly, the pH in the culture of L5 showedthe fast decline, with the final value significantly lower than those of other cultures. Strain L1 showed the least production of lactic acid. The culture supernatants of the five strains showed different degrees of antagonistic effect against pathogenic E. coli K88, K99, 987P, O141, E1, and 5. aureus. The inhibitory effect was more significant when the pH in the medium was low. When subtracting the effect of the acid, the culture supernatants still showed 22%~53% inhibitory effect, suggesting that apart from lactic acid the bacteria produced other inhibitory substances. The inhibitory effect of the culture supernatant was above 92% after heat treatment and above 85% when treated with proteases.In the fourth section, effects of gastrointestinal factors (low pH, bile salt and pepsin) on the survival of strain L5 and L7, and the heat tolerance of strain L5 were studied. The results showed that there was no obvious effect on the survival of L5 while incubating at pH over 2.5 for 150 min; and L5 was still able to survival well while incubating at pH1.5 for 30 min. Strain L7 exhibited a lower acid tolerance than L5, it was only able to survival at pH3.5 and 4.5. The survival of two strains was both inhibited by bile. The survival rates of L5 and L7 were 21.80% and 29.06% respectively after incubating in the medium with 0.1% of bile for 4 hours. The survival rates of two strains were both below 0.18% while the concentration of bile was over 0.2%. No significant effect of pepsin was observed on the growth of two strains. Heating at 50 癈 showed no effect on survival of L5 but heating over 80 癈 affect the survival of L5 significantly.更多还原