Abstract
Human κ-casein was tested as a bifidus growthpromoting factor before and after hydrolysis by chymosin or pepsin. The strain used was Bifidobacterium infantis SI2, originating from the feces of a breast-fed infant. Human κ-casein itself had bifidus growth-promoting activity without any treatment but became muchmore effective after treatment with chymosin or pepsin. Human glycomacropeptide, released by the action of chymosin or pepsin from human κ-casein, was effective as the factor even at low concentrations such as 50 ppm. By further hydrolysis with pronase, the activity was drastically decreased. This suggested that not only the sugar portion but also the polypeptide portion of human glycomacropeptide might play a significant role as a bifidus factor.
