【作者】 韩俊华；

【导师】 张柏林；

【作者基本信息】 河北农业大学 ， 农产品加工及贮藏工程， 2003， 硕士

【摘要】 嗜酸乳杆菌是寄主（人和动物）胃肠道系统中一个重要的微生物种类，当存在一定数量时，它能有利地平衡胃肠道系统中有益和有害微生物之间的平衡，从而对寄主的健康产生有益的影响，即益生特性（probiotic effects）。本文对嗜酸乳杆菌（Lactobacillus acidophilus）的部分益生特性及其在乳制品中的应用效果进行了研究，旨在为进一步研究其益生作用机理和开发相关的益生菌制品提供理论基础和科学依据。 对嗜酸乳杆菌菌株B、336、Ind-1和Lakcid在pH2.5以及1％的高胆盐环境中的耐受力进行了研究。结果表明，37℃厌氧培养4小时后，嗜酸乳杆菌在低pH和高胆盐环境中的存活率分别在40.2％～96.6％和70.0％～97.5％之间，各菌株均表现出较高的存活力。 研究表明，嗜酸乳杆菌菌株B、336、Ind-1和Lakcid具有一定的β-半乳糖苷酶活力，37℃厌氧培养18小时后，细胞释放的乳糖酶含量变化在0.29×10^-3U～2.00×10^-3U之间。各菌株对青霉素、氯霉素、庆大霉素和利福平表现出一定的耐受力，菌株之间存在一定差异。 胆盐水解酶检测和毛细管电泳分析数据表明，37℃厌氧条件下，嗜酸乳杆菌在特定的胆盐存在时，表现出较高的胆盐水解酶（BSH）活性。随着培养基中胆盐浓度的提高，嗜酸乳杆菌对胆盐的利用率也提高。培养基中胆盐的浓度为4.7069g／L和2.2663g／L时，嗜酸乳杆菌细胞的胆盐利用率分别在72.1％～94.9％和30.0％～46.6％之间。而且，菌株对胆盐的利用表现出一定的选择性，菌株之间也存在差异。 动物实验的结果表明，嗜酸乳杆菌具有显著降低小鼠血清胆固醇的能力（P＜0.05），对血清低密度脂蛋白和高密度脂蛋白具有一定的调节作用，并能降低小鼠患高血脂等症的风险指数。从总体上看，嗜酸乳杆菌B、336、Ind-1和Lakcid在减少和调节血清胆固醇的效果上，菌株之间未表现出明显差异。尽管嗜酸乳杆菌活菌制剂比嗜酸乳杆菌发酵奶具有更好的降胆固醇效果，但两种投放模式对血清胆固醇的影响差异也不显著。 对小鼠粪便的微生物组成分析表明，嗜酸乳杆菌B、336、Ind-1和Lakcid能够提高小鼠肠道中乳杆菌的数量，表明这种有益菌或许能良好地定植和存活在寄主肠道内。 37”C厌氧培养24 ’J’时后，嗜酸乳杆菌B、336、Indl和LakCid各累计产生0．73W0．78％的乳酸，均表现出较好的凝乳能力。各嗜酸乳杆菌发酵乳在 4”C下保存至 ZI天时，各菌株仍平均维持 2．gX10’Xf＼lltllL的活菌数，存活率在 87．7％～95．9％之间；发酵乳的滴定酸度达到1．10％以上；自由氨基酸含量从初始的120ppo缓慢上升到 160yg／thL。结果表明，在发酵乳中以及ZI天的保存期内，嗜酸乳杆菌不仅能维持较高的活菌数，而且可以保持较高的细胞活力，各菌株间没有明显的差别。 冷冻干燥技术能显著提高嗜酸乳杆菌的活菌数至 10‘tm／g以上。存活数据表明，4OC条件下保藏20大后，嗜酸乳杆菌的活菌数仍维持在 10‘tfu／g以上，基本不变；与冻干前相比，冻干后嗜酸乳杆菌细胞的水解蛋白活力有一定程度的下降。更多还原

【Abstract】 Lactobacillus acidophilus, as one of the species naturally occurring in the gastrointestinal tract of host (human and animals), may offer various health-promoting effects (probiotic effects) to individuals by balancing the host intestinal microflore between beneficial and harmful microorganisms. Consumption of food products supplemented with the bacterium produces some claimed nutritional and health benefits including improvement of lactose intolerance, inhibition of pathogenic organisms, stimulation of immune system, reduction of serum cholesterol and suppression of tumor cells. The objectives of this study were: (1) to investigate some probiotic properties produced by the four selected strains of I. acidophilus (B, 336, Ind-1 and Lakcid) and (2) to examine their practical applications in selected dairy products.The tolerances of L. acidophilus strains to low pH of 2.5 and 1% bile salt were studied. Simulation of the gastrointestinal environments showed that after anaerobic incubation at 37癈 for 4 hrs, the survival rates of the strains ranged from 40.2% to 96.6% in pH 2.5 and from 70.0% to 97.5% in 1% bile salt solution, respectively. All the strains showed a proper resistance to the extreme stresses and perhaps survived in host intestines.L. acidophilus strain B, 336, Ind-1, and Lakcid exhibited different p-galactosidase activities. The levels of P-galactosidase released from cells varied from 0.29x10-3 U to 2.00x10-3 U, depending on the used strains which were incubated at 37癈 anaerobically for 18 hrs. The susceptibility of the four strains to antibiotics indicated that the probiotic bacterium was able to tolerate to low concentration of chloramphenicol (0.0244mg/mL~0.39mg/mL), gentamicin(31.25U-500U), penicillin(7.81U~31.24U) and rifampin(0.195ug/mL~3.12ug/mL) usually used in clinic practice. Clearly, the susceptibility of antibiotics was strain-dependent.Under anaerobic conditions with an incubation of 37癈 L. acidophilus strain B, 336, Ind-1, and Lakcid formed white precipitated-zone colonies in MRS modified medium containing bile salts plus CaCh. It meant that the probiotic bacterium had an ability toproduce bile salt hydrolase (BSH) and de-conjugate bilt salt. The higher the concentration of TDCA was in medium, the more its concentration decreased according to the studied strains. At two given TDCA concentrations 4.7069g/L and 2.2663g/L, the deconjugation rates were 72.1% to 94.9% and 30.0% to 46.6% respectively. Moreover, the strains studied showed a preference in the utilization of different forms of bile salts.The results showed that the level of serum total cholesterol decreased significantly in tested rats fed successively with high-fat feedings and supplements of L. acidophilus strains B, 336, Ind-1 and Lakcid. And the four strains showed positive effects both on the alleviation of LDL or HDL and on the reducing of RF (TC/HDL). However, no clear difference was found among these studied strains. Direct oral administration of L. acidophilus live cells to rats would produce a better effect in the reduction of cholesterol than that of acidophilus fermented milk, but they showed no significant difference.Compared to the control group, those rats consuming the supplements of L. acidophilus strain B, 336, Ind-1, and Lakcid largely increased the number of lactobacilli in their fecal samples. It further proved that L. acidophilus might survive and colonize in the intestinal tract of tested rats, showing the possibilities of its probiotic effects.L. acidophilus strain B, 336, Ind-1 and Lakcid produced 0.73%~0.78% lactic acid when incubated at 37癈 in milk for 10 hrs and coagulated milk very well. When the acidophilus fermented milks were under refrigerated storage at 4癈, the viable cells of L. acidophilus averagely were 2.9x108 cfu/mL and the viable rate varied from 87.7% to 95.9% depending on strains used. The titratable acidity of the acidophilus fermented milks increased gradually to above 1.10%. The free amino acid from the hydrolysis of milk proteins rose gradually from 120ug/更多还原