[Fermentation and polysaccharide antioxidative activity of a Libertella strain]

To study fermentative production of exopolysaccharide (EPS) from a Libertella sp. and to evaluate its antioxidant activity.

We studied the effect of carbon source, nitrogen source, growth factors, pH and culture time on the production of Libertella exopolysaccharide. By determining the reduction capability, the decoloration of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the elimination of hydroxyl radicals, we evaluated the antioxidant activity of the Libertella exopolysaccharide.

The optimum conditions for Libertella exopolysaccharide production were in a medium containing potato juice 20%, maltose 20 g/L, (NH4)2SO4 5 g/L and L-cystine 0.01 g/L and at pH 5.0 and 25 degrees C fermented for 10 d. Under this condition, exopolysaccharide concentration in the fermentation broth reached 37.52 mg/L, 84.10% higher than that of the control. The scavenging effects of the Libertella exopolysaccharide on 1,1-diphenyl-2-picrylhydrazyl radical reached 14.21% with 20 mg/L exopolysaccharide, and the clearance rate of hydroxyl radicals reached 50.81% with 50 mg/L exopolysaccharide.

The ferment conditions have significant influence on the production of Libertella exopolysaccharide. The exopolysaccharide showed obvious antioxidant activity.