Yuka Isobe

Production of a Novel Extracellular Polysaccharide by a Bacillus Strain Isolated from Soil

A bacterium that was isolated from soil and identified as Bacillus circulans was found to produce a highly viscous extracellular polysaccharide when it was grown aerobically in a medium containing glucose as a sole source of carbon. The product was characterized by TLC and GC analyses as a novel heteropolysaccharide consisted of rhamnose, mannose, galactose, and mannuronic acid as sugar components. A maximal yield of polysaccharide reached about 2 g/liter by jar-fermentor culture at 30°C for 48 hr with a medium containing 1% glucose, 0.05% asparagine, 0.005% yeast extract, and small amounts of inorganic salts. Some culture conditions for the production of polysaccharide were investigated with flask culture; an optimal production was attained with a medium containing 0.1-1 % glucose and 0.01-0.05% asparagine, pH 7-8, at 30°C under aerobic conditions.

Properties of a Highly Viscous Polysaccharide Produced by a Bacillus Strain Isolated from Soil.

Chemical and Theological properties of a highly viscous and acidic polysaccharide produced by a soil bacterium identified as Bacillus circulans are described. The molecular weight of the native polysaccharide was about 116 × 10(4) by gel filtration with HPLC. The molar ratio of D-galactose, n-mannose, and L-rhamnose contained in the polysaccharide as neutral sugar components was 1.3:1:2. The viscosity of 1% solution of the polysaccharide was about 5000 cp, which was higher than that of guar gum, a seed polysaccharide, used as a reference standard. The viscosity was affected by the pH of the polysaccharide solution, a maximum viscosity being observed at pH 5.5 for native and decationized polysaccharide solution. The viscosity of 0.3% solution was decreased to about 70% by heating at 100°C and 22% at 120°C for 30 min as compared to the viscosity before heating. The addition of sugars, especially sucrose and glucose, at 10-30% concentration brought about a 130-180% increase of the viscosity. The addition of CaCl2 at a low concentration markedly increased the viscosity, and a maximum viscosity was attained at 2% concentration of the salt.