Undialyzable Growth Factors for Lactobacillus bifidus var. pennsylvanicus

Lactobacillus bifidus var. pennsylvanicus requires human milk constituents for growth. All growth factors so far known represent low‐molecular derivatives of d ‐glucosamine (2‐amino‐2‐deoxy‐ d ‐glucose). Some higher‐molecular undialyzable sialic acid‐containing oligosaccharides from human milk and some sialo‐glycoproteins from different body fluids have been tested for growth promoting activity. Isolation, purification and some structural properties of the oligosaccharides are described. Without pretreatment by neuraminidase, none of the substances exhibit any growth promoting activity. After incubation with neuraminidase from Vibrio cholerae , the activity of the oligosaccharides increased in close correlation to the content of N ‐acetyl‐ d ‐glucosamine to the same extend as ethyl‐2‐acetamido‐2‐deoxy‐β‐ d ‐glucopyranoside, the most active derivative of N ‐acetyl‐ d ‐glucosamine known. The activity of α 1 ‐acid glycoprotein from human serum, urinary glycoprotein and submaxillary mucin was considerably lower, possibly due to the different linkages of sialic acid and their more complex structures. The possible protective effect of sialic acid bound to oligosaccharides and glycoproteins against degradation by bacterial enzymes is discussed.