Isolation and characterization of an extracellular polysaccharide from Pseudomonas caryophylli CFR 1705

Extracellular polysaccharides were isolated from Pseudomonas caryophylli CFR 1705 grown on lactose containing medium. The major fraction (no.1) obtained on DEAE-cellulose chromatography was composed of rhamnose, mannose and glucose in the ratio 1:3.26:4.97, respectively, and having a molecular weight of 1.1×106 Da. Methylation followed by GC-MS analysis revealed it to be a highly branched 1,4-linked hexosan with mannose and glucose as the branch-off residues at positions C-2 and C-6 of the main chain. Rhamnose was essentially found as non-reducing terminal residue.