Although some Lactobacilfus strains are reported to produce extracellular poly-saccharidesi4, nothing is known of their structure. We recently isolated a capsular polysaccharide-producing Lactobacillus kejiranofaciens from kefir grain?'. The polysaccharide extracted from kefir grains was named kefiran and its structure was elucidated by Kooiman12: it has a branched hexasaccharide repeating-unit. However, methylation analysis of the polysaccharide from L. kefiranofaciens suggested that it is very similar to kefiran but at the same time has an unknown structural part". We have here attempted to elucidate the complete structure of the capsular polysaccharide from L. kefranofaciens strain K,. This is the first report concerning structural analysis of extracellular polysaccharide from Lactobacillus species.
When L. kejiranofuciens K, was grown for 3 days at 30" in IKPL medium13, the culture became viscous due to the production of extracellular polysaccharide. India ink stainI showed that the polysaccharide is a capsular type. The polysaccharide fraction obtained from the culture supernatant has been shown by methylation analysis" to have the same structure as that from the capsule. In this paper, the supernatant was used for the structural study because of its facility in purification. The purified polysaccharide was obtained in a yield of 63 mg/L from the culture supematant. It gave a single peak by gel filtration chromatography on an h.p.1.c. column (Asahipak GS-710) and had mol.wt. 1.0 x 106. The polysaccharide had [a], +54" (c 1.0, water), was composed of only D-glucose and D-galactose in the molar ratio of 0.9:l.l) and did not contain nitrogen.
To obtain information concerning the glycosyl sequence, the polysaccharide was treated with alpha-amylase, galactanase", Zymolyase-20T, and cellulase. Only cellulase hydrolyzed the polysaccharide, giving -80% of D-glucose, o-galactose, and an oligosaccharide 1 in the moIar ratio of 1.0:0.3: 1 .O. F.a.b.-m.s. of the oligosaccharide 1 gave