Abstract:

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.

Key words: real-time polymerase chain reaction, casein glycomacropeptide (CGMP), Bifidobacterium, mouse feces