Purification and fractionation of lipopolysaccharide from gram-negative bacteria by hydrophobic interaction chromatography.

By hydrophobic interaction chromatography on octyl-Sepharose, lipopolysaccharide (LPS) of Escherichia coli Re mutant and of wild-type smooth-form (S-form) Salmonella typhimurium and Salmonella abortus equi is fractionated according to increasing amount of fatty acids. Thereby a fractionation of S-form LPS according to the length of the O-polysaccharide chain also occurs, because with increasing of fatty acids there is a decrease in the mean length of the O-polysaccharide chain from approximately 30 to 4 repeating units. Molecular species of Re-mutant LPS contain four 3-hydroxytetradecanoyl residues in addition to which dodecanoic, tetradecanoic and possibly hexadecanoic acid, appear in this sequence. Among the molecular species of S-form LPS, dodecanoic, tetradecanoic and hexadecanoic acids appear in the same order, but in contrast to Re-mutant LPS a significant fraction of S-form LPS contains less than four 3-hydroxytetradecanoyl residues. Hydrophobic interaction chromatography also proved an effective one-step purification procedure of LPS as was shown with a crude preparation from S-form S. typhimurium.