A New Gel-Forming Polysaccharide Produced by Bacillus subtilis FT-3 Its Structure and its Physical and Chemical Characteristics

A bacterium which produces an extracellular agar-like gel-forming polysaccharide was isolated and named Bacillus subtilis FT-3. Under optimal conditions for cultivation, a colorless filamentous polysaccharide was obtained. The yield was about 3.5g per liter of culture broth. The polysaccharide was found to be homogenous from the results of various physical measurements. It was an acidic heteropolysaccharide composed of glucose, galactose, fucose, glucuronic acid, and O-acetyl groups in an approximate molar ratio of 2:2:1:1:1.5. It formed an agar-like gel when an aqueous suspension of more than 1% was heated in boiling water and allowed to stand at room temperature. A dilute aqueous solution of FT-3 polysaccharide (e.g. 0.5%) was as viscous as 200～300 centipoise, and exhibited streaming birefringence, suggesting a rigid rod-like structure in solution. The results of Smith degradation, methylation, and partical acid hydrolysis provided the following main chain sequence for this polysaccharide. [numerical formula] n=35～40 The structure was also investigated by the alkaline OPD method and a specific quinoxaline formation from the glycosidic linkage of the polysaccharide was confirmed. The phenomena of polysaccharide gel formation are discussed in connection with the comparison of FT-3 polysaccharide and other polysaccharides