The effect of different milks and milk proteins on the growth of Bifidobacterium infantis ATCC 27920 in vitro.

Bifidobacteria is a well known bacteria that is found in abundance in the intestine of infants which provides several health and nutritional benefits. Realizing the many benefits of bifidobacteria to human, this study has been conducted with the objective to determine the growth promotional effect of different types of milk and milk proteins on Bifidobacterium species. One strains of Bifiodobacterium species that is B. infantis was used to study the growth promoting effect of human milk, cow's milk, goat's milk, milk based infant formula, soy-based infant formula, lactoferrin (1 mg/ml), lactoperoxidase (1p~g/ml), lysozyme (1 mg/ml) and the mixture of these three proteins. The growth promotion assay was done using the 96-well culture plates which consists of 200 (1 Trypticase-Peptone-Yeast extract (TPY) medium, 50 4 sample and 10 1il of bacteria inoculum. Control consists of PBS instead of the samples. The assay was incubated anaerobically at 370C for 18 hours before being spread on the agar plate containing TPY medium with agar. Comparison was made between the mean count (log cfu/ml) of different types of milks, between infant formula and between milk proteins. From the results, Oneway ANOVA test at P<0.05 showed that there was significant differences in the mean counts (log cfu/ml) between the milks (P = 0.0000). A similar trend was observed in the mean count (log cfu/mI) between the infant formulas (P = 0.0 124) and also between the milk proteins (P = 0.0005). Duncan Multiple Range tests showed that there was significant differences between all the milks and control and among the milks themselves. There was however, no significant difference among the two types of infant formulas. The milk proteins also showed significant differences between the proteins and control and among themselves except for lysozyme which showed no significant differences with lactoferrin. This study showed that the growth of B. infantis could be promoted by different kinds of milks and milk proteins in vitro. Comparing the differences in growth promoting effect between samples and control indicated that human milk has the highest growth promoting effect followed by cow's milk and the mixture of the three milk prtoeins. Lysozyme showed the lowest in term of differences in percentage of growth promoting effect among all these samples. In conclusion the findings of this study supported that human milk ios the best milk choice for infant in comparison to other types of milk in promoting the growth of bifidobacteria. In additon, this tudy also found that milk protein when used in combination may show better growth promoiotive effect than when used singly.