Effects of glycomacropeptide in human milk and formula milk on proliferation of bifidobacterium infantis in vitro

Abstract

Objective To explore the effects of glycomacropeptide (GMP) in human milk and formula milk on proliferation of bifidobacterium infantis and their dose-response relationship. Methods Casein was isolated from the milk of 30 healthy postpartum women from Guangzhou Women and Children's Medical Center in September 2014, and hydrolyzed by rennet to obtain GMP, which was then purified by ultrafiltration and ion exchange chromatography. Human milk GMP and cow milk GMP (0, 250, 500, 1 000,1 500, 2 000 and 3 000 mg/L) were added to bifidobacterium infantis liquid medium, and cultured under anaerobic conditions. Concentration of bacteria was measured by turbidimetric microplate assay (detection of OD600 nm value of medium). Difference of proliferative activities of bifidobacterium infantis in human milk GMP and cow milk GMP was compared with independent samples t-test. Results Purified human milk GMP concentration was 1 712.20 mg/L, with a purity of 80.3%. Increasing the cow milk GMP initial concentration in the culture medium at 250-2 000 mg/L could increase the concentration and proliferation rate of bifidobacteria infantis. When cultured at 36 h with GMP of various concentrations, the proliferation of bifidobacteria infantis maintained at a logarithmic phase. Therefore, 36 h was chosen as the test time point to compare the proliferation of bifidobacterium infantis. At 36 h, when GMP in the medium was 1 000, 1 500, 2 000 and 3 000 mg/L, concentrations of bifidobacteria infantis in human milk GMP were 2.255±0.036, 2.583±0.088, 2.877±0.080 and 3.219±0.081, respectively, which were significantly higher than those in cow milk GMP (2.115±0.053, 2.312±0.064, 2.542±0.090 and 2.894±0.076; t=4.867, 5.569, 6.192 and 6.516; all P<0.01). Conclusions Both human milk GMP and cow milk GMP can promote the proliferation of bifidobacterium infantis in vitro, and the proliferative activity in human milk is greater than in cow milk at the same concentration of GMP. Key words: Milk, Human; Infant formula; Caseins; Peptide fragments; Bifidobacterium