Preparation of oligosaccharides by bacteriophage degradation of polysaccharides from Klebsiella serotypes K21 and K32

Depolymerization of bacterial, capsular polysaccharides by phage enzymes is a convenient method of preparing oligosaccharides that correspond to one, or several, repeating unit(s). Thus, the capsular polysaccharide from Klebsiella K21 yields a linear pentasaccharide, and that from Klebsiella K32, a linear tetrasaccharide. Both oligosaccharides contain acetal substituents, but, whereas the 4,6-O-(1-carboxyethylidene)-D-galactosyl residue in the K21 structure is relatively acid-stable, the corresponding 3,4-O-(1-carboxyethylidene)-l-rhamnosyl residue in K32 is extremely acid-labile. Phage degradation may, therefore, be the only way by which an oligosaccharide corresponding to an intact repeating-unit may be obtained in such circumstances.