Abstract: This paper deals with the optimization of process conditions for the extraction of polysaccharides from Nostoc commune using one-factor-at-a-time and orthogonal array design methods. Meanwhile, the antibacterial activity of polysaccharides from Nostoc commune was tested by the filter paper disc diffusion method. The results showed that extraction temperature and time influenced the extraction efficiency of polysaccharides from Nostoc commune at an extremely significant level and at a significant level, respectively. The optimal extraction conditions were temperature of 90 ℃, extraction time of 3 h, material-liquid ratio of 1:15, and repeated extraction number of 2. The resulting extract revealed good antibacterial activity against Escherichia coli, Bacillus subtilis, Serratia marcescens, Aspergillus nigere and Candida albicans with minimum inhibitory concentration (MIC) of respectively 50, 50, 25, 100 mg/mL and 100 mg/mL.

Key words: Nostoc commune, polysaccharide, extract, antibacterial