Aims To purify and characterize an exopolysaccharide (EPS) from an Agrobacterium strain ZCC3656 with high EPS-secreting performance and investigate its anti-inflammatory activity using lipopolysaccharide (LPS)-induced macrophage cells in an acute liver injury mouse model. Methods and Results Twelve rhizobial strains were compared for EPS fermentation production in modified M9 salts supplemented with mannitol or sucrose as the sole carbon source. Agrobacterium sp. ZCC3656 exhibited the highest EPS yield (21 center dot 1 g l(-1)) and was characterized for EPS production by carbon source utilization, time course fermentation and serial subcultivation assays. The EPS, designated Riclin, was purified by deproteinization using the Sevag method. The combined results of gel permeation chromatography, monosaccharide composition, methylation analysis and nuclear magnetic resonance analyses indicated that Riclin is a succinoglycan-like polysaccharide comprised of glucose, galactose, succinate and pyruvate at a ratio of 7 center dot 8. : 1 center dot 0 : 0 center dot 9 : 1 center dot 1 and has an molecular weight of approximately 2 center dot 5 x 10(6) Da. Riclin inhibited TNF-alpha, IL-1 beta and IL-6 expression in LPS-stimulated RAW 264.7 macrophage cells in a dose-dependent manner. In addition, Riclin pretreatment increased the survival rate of D-Gal/LPS treated mice, inhibited serum ALT and AST activities and reduced the production of the inflammatory mediators TNF-alpha, IL-1 beta and IL-6. Conclusions Agrobacterium sp. ZCC3656 is a highly stable EPS-producing strain. The EPS Riclin from ZCC3656 is a succinoglycan-type polysaccharide that is noncytotoxic and exhibits remarkable anti-inflammatory effects in vivo and in vitro. Significance and Impact of the Study Succinoglycans are well known for good rheological properties and their physiological interactions with plants. However, their potential activity towards mammals has received little attention. Our study revealed that the succinoglycan Riclin exhibited excellent anti-inflammatory activities and could be considered as a promising reagent in anti-inflammatory treatment.