Structural studies of the capsular polysaccharide of Acinetobacter calcoaceticus BD4

Compositional analysis of the intact and carboxyl‐reduced capsular polysaccharide of Acinetobacter calcoaceticus BD4 (PS‐4) showed it to consist of l‐rhamnose, d‐glucose, d‐glucuronic and d‐mannose in molar ratios of 4:1:1:1. ¹³C‐nuclear magnetic resonance spectroscopy, methylation analysis, oligosaccharide analysis and base‐catalyzed β‐elimination were used to elucidate the primary structure. Oligosaccharides were obtained by enzymatic depolymerization with a specific bacteriophage‐induced depolymerase and by partial acid hydrolysis. From the results it is concluded that PS‐4 consists of repeating units of the heptasaccharide (Formula Presented.) The bacteriophage‐induced depolymerase was found to be an endo‐β‐d‐glucosidase that hydrolyzed the bond β‐d‐Glc‐(1→3)‐l‐Rha to generate a heptasaccharide in 40% yield.