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United States Department of Agriculture

Agricultural Research Service

Title: Production of An Extracellular Polysaccharide by Agrobacterium Sp. Ds3 Nrrl B-14297 Isolated from Soil

item Hou, Ching
item Brown, Wanda
item Ahlgren, Jeffrey
item Nicholson, James

Submitted to: Journal of Industrial Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 1995
Publication Date: N/A

Interpretive Summary: Viscous polysaccharides, produced by plants and microorganisms, are very useful in our daily life. They are used as blood extender and thickening agents for food and other industrial applications. We are screening microorganisms for converting agricultural commodities such as soybean oil to value-added products. Recently, we isolated a new microbial strain, Agrobacterium DS3 which produced a new viscous polysaccharide at a good yield. This DS3 polysaccharide, like well-known dextran and xanthan gum, may be used in many food, medical and industrial applications.

Technical Abstract: A bacterium isolated from soil and identified as an agrobacterium was found to produce a water-soluble extracellular polysaccharide capable of producing highly viscous solutions. Gas chromatography analysis showed that the polymer consists of glucose, galactose and mannose at a ratio of 7.5:2.4:1. Following methylation and periodate oxidation, the polysaccharide was shown to consist 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. It also contained pyruvic acid at 3.7% by weight and did not contain succinic acid, which is different from succinoglycan or the water insoluble beta-(1--3)-glucans (i.e., curdlan). The molecular weight of the polysaccharide was estimated to be 2 x 10(6) Da by light scattering. The viscosity of solutions containing the polysaccharide remained constant from pH 3 to 11, and decreased by 50% when heated from 5 to 55C. The maximum yield of the polysaccharide production, 20 g/L, was reached at 48 h and 30C incubation.

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