中文摘要：

采用实时荧光定量聚合酶链式反应（real-time polymerase chain reaction，real-timePCR）分析不同剂量酪蛋白糖巨肽（casein glycomacropeptide，CGMP）对小鼠肠道双歧杆菌增殖水平的影响，揭示乳源CGMP是否有增殖肠道关键益生菌的功能。选用50只健康BALB／cdx鼠，随机分为对照组，安慰组（灌胃生理盐水0．2mL），乳源CGMP低、中、高剂量组（灌胃等体积不同质量浓度的乳源CGMP），灌胃周期为2周。于灌胃后第0、3、5、7、9、11、15天及停止灌胃后1周（第21天）采集的小鼠新鲜粪便，并进行粪便菌体基因组DNA抽提。依据双歧杆菌的16SrRNA基因序列设计5对种属特异性引物，以两歧双歧杆菌（Bifidobacterium bifidum）CICC6071的基因组DNA作为标准品，进行梯度稀释制作标准曲线；分析样品PCR扩增产物的熔解曲线，评价反应的特异性。结果表明：Real-timePCR可准确定量小鼠肠道内双歧杆菌数量；且灌胃中剂量乳源CGMP可以促进小鼠肠道内双歧杆菌的增殖，在灌胃第11天时小鼠肠道内双歧杆菌数量达到最高值，即乳源CGMP对小鼠肠道双歧杆菌的增殖作用存在剂量选择性。

英文摘要：

Purpose： To analyze the growth-promoting effects of different doses of casein glycomacropeptide （CGMP） on intestinal bifidobacteria in mice by quantitative real-time polymerase chain reaction PCR （qRT-PCR）, which reveal whether or not CGMP derived from milk is able to proliferate the key intestinal probiotics. Methods： A total of 50 healthy BALB/c mice were randomly divided into five groups： control group （daily diet）, placebo group （0.2 mL of normal saline）, low-, moderate-, high-dose CGMP treatments （the same volume as normal saline at different concentrations）. The administration duration was 2 weeks. We took the fresh feces of mice after 0, 3, 5, 7, 9, 11, 13 and 15 consecutive days of once-daily administration and at 6 days after the last administration for genomic DNA extraction. Five pairs of group-specific primers for bifidobacteria were designed according to 16S rRNA sequence. Bifidobacterium bifidum CICC6071 was used to make the standard curve by gradient dilution to determine the response sensitivity. The melting curves of PCR products were used to evaluate the specificity. The results indicated that qRT-PCR could accurately quantify the number of mouse intestinal bifidobacteria. The moderate dose of CGMP could promote the growth of bifidobacteria and the number of bifidobacteria reached the maximum after 11 days of administration. This study demonstrates that CGMP from milk has the function of regulating the mouse intestinal bifidobacteria in a dose-dependent manner.