Effect of molecular weight on the antibacterial activity of polysaccharides produced by Chaetomium globosum CGMCC 6882.

This study investigated the effect of molecular weight on antibacterial activity of polysaccharides. Results showed that low molecular weight (3.105 × 104 Da) polysaccharide (GCP-2) had higher inhibitory effects against Escherichia coli and Staphylococcus aureus than high molecular weight (5.340 × 104 Da) polysaccharide (GCP-1). Meanwhile, antibacterial activities of GCP-2 and GCP-1 against S. aureus were higher than those of E. coli. Minimum inhibitory concentrations (MICs) of GCP-1 against E. coli and S. aureus were 2.0 mg/mL and 1.2 mg/mL, and MICs of GCP-2 against E. coli and S. aureus were 1.75 mg/mL and 0.85 mg/mL, respectively. Antibacterial mechanisms investigation revealed that GCP-2 and GCP-1 influenced cell membrane integrity, Ca2+-Mg2+-ATPase activity on cell membrane and calcium ions in cytoplasm of E. coli and S. aureus, but not cell wall. Present work provided important implications for future studies on development of antibacterial polysaccharides based on molecular weight feature.