Production of an extracellular polysaccharide by agrobacterium sp DS3 NRRL B-14297 isolated from soil

Abstract

A bacterium isolated from soil and identified as Agrobacterium sp produced a water-soluble extracellular polysaccharide capable of producing highly viscous solutions. Gas Chromatographic analysis revealed a sugar composition of glucose, galactose and mannose in the molar ratio of 7.5 : 2.4 :1, together with 3.7% (w/w) pyruvic acid. Methylation analyses showed the presence of (1 → 3)-, (1 → 4)- and (1 → 6)-linked glucose, (1 → 3)- and (1 → 4, 1 → 6)-linked galactose and a small portion of (1 → 3)-linked mannose residues. Succinic acid was not present. The molecular weight of the polysaccharide was estimated by light scattering to be 2 × 106 Da. The viscosity of solutions containing the polysaccharide remained constant from pH 3 to 11, and decreased by 50% when heated from 5 to 55°C. Maximum yield of the polysaccharide, 20 g L-1, was reached in 48 h at 30°C incubation. © 1996 Society for Industrial Microbiology.