PURPOSE: To obtain a polysaccharide useful in food processing, by culturing polysaccharide-producing bacteria belonging to Genus Rhizobium in a nutritious culture medium and thereby producing a polysaccharide.

CONSTITUTION: A polysaccharide having an ability to form a thermoreversible gel and containing as the principal constituents glucose, galactose, glucuronic acid and ribuloic acid present in a mol or ratio of 5:1:1:1 is prepared by culturing polysaccharide-producing bacteria belonging to Genus Rhizobium in a nutritious culture medium. Then, the produced polysaccharide is collected. The microorganisms used are those belonging to Genus Rhizobium, and include, for example, Rhizonium meliloti. As the nutritious culture medium, there is advantageously used a liquid culture medium containing a carbon source such as gluclose, a nitrogen source such as ammonium chloride, an inorganic salt such as calcium phosphate and, if necessary, a growth-promoting substance such as vitamins and yeast extract.