Enzymatic synthesis of a growth factor for Lactobacillus bifidus var. Penn.

It has been shown (1, 2) that in human milk there are N-acetyl-n-glucosamine-containing oligosaccharides which promote the growth of Lactobacillus bifidus var. Penn. In the search for substances with lower molecular weight which would still show a growth-promoting effect in the microbiological test, activity was found in mildly hydrolyzed chitin of crab and lobster shells,’ in P-methyl N-acetyl-n-glucosaminide, but not in the pure corresponding a-methyl glycoside (3) and in a crystallized disaccharide composed of N-acetyl-n-glucosamine and galactose, isolated from acid-hydrolyzed gastric mucin (4). A crude, cell-free enzyme preparation, prepared from cells of L. bifidus var. Penn by grinding with alumina, extracting with 0.01 M phosphate buffer at pH 6.3, and lyophilizing the supernatant fluid, hydrolyzes these growth factors with liberation of N-acetyl-nglucosamine which is only slightly active microbiologically (5). This same enzyme preparation, permitted to act upon a mixture of N-acetyl-nglucosamine and lactose, may increase the apparent activity of N-acetyl-nglucosamine up to 300 per cent. A very active N-acetyl-nglucosaminecontaining disaccharide has been found in such digests. The isolation and characterization of this compound and of an isomeric disaccharide are described in the present communication.