Structural characteristics and anti-tumor activities of a novel polysaccharide from Klebsiella sp. SXW12.

The purpose of this study is to elucidate the structure and biological properties of an extracellular polysaccharide (EPS), named EPS12, produced by Klebsiella sp. SXW12, a strain isolated from pond sludge. The maximum EPS12 yield of 15 g/L was obtained after optimizing the fermentation conditions by single-factor effects. EPS12 was an acidic homogeneous polysaccharide, and the molecular weight was measured to be 9.39 × 104 Da. Monosaccharide composition, methylation analysis, and NMR showed that EPS12 backbone was →3)-β-D-Glcp-(1 → 4)-β-D-GlcpA-(1 → 4) -α-L-Fucp-(1→, and terminal-β-D-Glcp was connected to the O-4 of →3)-β-D-Glcp-(1→. Network pharmacology analysis suggested that EPS12 may have anti-cancer effects. The anti-tumor effect of EPS12 on LLC-LUC tumor mice was studied. The results indicated that EPS12 exhibited excellent anti-tumor activity in mice at low doses (1, 2, and 4 mg/kg body weight). In vivo, EPS12 increased spleen index, promoted lymphocyte proliferation, and reduced spleen cell apoptosis through the Bcl-2-Bax/Bak-Caspase-3 apoptotic signaling pathway, and exhibited good biosafety. In addition, EPS12 could partially regulate the metabolic profiles of splenocytes. These properties make EPS12 a potential efficient and cost-effective anti-tumor agent or health product.