降胆固醇乳酸菌的筛选及其生物学特性研究

【作者】 张德珍；

【导师】 潘道东；

【作者基本信息】 南京师范大学 ， 微生物学， 2005， 硕士

【摘要】 人类跨入科学技术飞速发展的21世纪,人民的生活水平大幅提高,人们的膳食营养也相应增加,随之而来的问题就是胆固醇的摄入量很容易超标。而高血胆固醇与动脉粥样硬化、冠心病、脑中风等心脑血管疾病之间具有密切的关系。一般来说,血胆固醇浓度每上升1%,冠心病死亡率则上升2%。可见,保持血液中胆固醇浓度在正常范围内对于预防动脉粥样硬化和心脑血管疾病是至关重要的。因此,寻找不影响食品风味,经济实用的降低食品及人体血清胆固醇水平的方法已成为当前重要的研究课题。本研究通过体外筛选从食品中分离得到一株体外降胆固醇能力为41.87%的乳酸菌LQ-12。对乳酸菌LQ-12的体内降胆固醇特性研究,用乳酸菌LQ-12发酵酸奶饲喂高脂模型大鼠,观察其对血清总胆固醇(TC)、血清甘油三酯(TG)、血清高密度脂蛋白(HDL-C)、血清总胆酸(TBA)、肝脏总胆固醇(TC)、粪便总胆固醇(TC)、粪便总胆酸(TBA)以及体重和脏体比(肝重/体重、肾重/体重、脾重/体重)的影响。结果发现,28d后,与高脂模型组相比,实验组大鼠血清中TC、TG和TBA含量明显下降(P<0.05);粪便中TC含量升高,而TBA含量降低;肝重/体重显著降低。各组间大鼠的HDL-C、体重、肾重/体重、脾重/体重无显著差异。通过ATB细菌鉴定仪鉴定乳酸菌LQ-12为乳酸乳球菌乳亚种。对乳酸菌LQ-12在模拟胃肠环境条件下的抗性研究表明,乳酸菌LQ-12在pH1.5～4.5生活4h活菌数仍达10~6CFU/mL以上,在0.1%～0.3%(m/v)胆汁盐条件下4h活菌数仍达10~6CFU/mL以上。同时对致病性大肠杆菌和金黄色葡萄球菌具有明显的抑制作用,且对氨苄青霉素、四环素、庆大霉素、严迪(主要成分为罗红霉素)和头孢拉定有耐药特性。以pH值、酸度、活菌数、发酵时间和感官评价为指标,得出了利用乳酸乳球菌乳亚种LQ-12发酵具有降胆固醇功效的功能性酸奶的最优化条件为绵白糖6%(w/v),菌种配比为1:2(杆菌:球菌),发酵温度为45℃,番茄汁添加量为6%(v/v)。食品安全性评价表明,乳酸乳球菌乳亚种LQ-12发酵乳对小鼠无急性毒性,对小鼠精子也不产生畸变作用。因此可初步评价乳酸乳球菌乳亚种LQ-12发酵乳口服比较安全。可用作微生态制剂和功能性乳酸制品发酵剂的优良菌种。更多还原

【Abstract】 Cardiovascular disease (CVD) is a leading cause of death in the world.Diet has been identified as a means of controlling serum cholesterol concentrations,and many health conscious people are adopting measures to decrease risk by reducing blood cholesterol and perhaps triacylglycerols.Several investigations have reported that a fermented milk product with lactic acid bacteria appears to have an action to decrease serum cholesterol concentration.In this study, Cholesterol-reducing strains LQ-12 which was identified as Lactococus.lactis subsp. lactis was screened from commercial food.41.87% cholesterol reduced in MRS which contained cholesterol when incubated with LQ-12. The effect of the yogurt fermented with strain LQ-12 on the SD rats showed that the mean values for serum TC,TG,TBA and faecal TBA concentrations decreased significantly (P<0.05),TC in faecal increased at the same time,while serum HDL-C concentrations were not significantly increased after 28d’s fedding. As imitating gastroenteric environments, the study on Antagonistic property of LQ-12 indicated that LQ-12 survived at pH 1.5-4.5 after 4h culture and the living bacterial number could reach 10~6CFU/mL; that living bacterial number were also above 10~6CFU/mL at the 0.1%~0.3%(m/v) bile salt and even survived in 0.4% after 6h culture-, that antimicrobial activities to the pathogenic E.coli and S.aureus were obvious; and that the tolerance to Ampicillin, Tetracycline, Gentamicin, Roxithromycin, Cefradine was power.The best fermenting condition of LQ-12 was that 6% (w/v) of suger, Lactobacillus. acidophilus:LQ-12 of 1:2, temperature of 45℃, 6%(v/v) of tomato juice . Acute toxicity test and sperm shape abnormality test showed that the yogurt fermented with strain LQ-12 have no influnce on Acute toxicity and sperm shape abnormality in mice.So LQ-12 can be used as microbial preparation and starter for yogurt.更多还原