Abstract

Rhamsan gum is a type of water-soluble exopolysaccharide produced by species of Sphingomonas bacteria. The optimal fermentation medium for rhamsan gum production by Sphingomonas sp. CGMCC 6833 was explored definition. Single-factor experiments indicate that glucose, soybean meal, K2HPO4 and MnSO4 compose the optimal medium along with and initial pH 7.5. To discover ideal cultural conditions for rhamsan gum production in a shake flask culture, response surface methodology was employed, from which the following optimal ratio was derived: 5.38 g/L soybean meal, 5.71 g/L K2HPO4 and 0.32 g/L MnSO4. Under ideal fermentation rhamsan gum yield reached 19.58 g/L ?1.23 g/L, 42.09% higher than that of the initial medium (13.78 g/L ? 1.38 g/L). Optimizing the fermentation medium results in enhanced rhamsan gum production.

• Keywords: Sphingomonas sp. CGMCC 6833; rhamsan gum; medium optimization; central composite experimental design