Abstract: The accumulation of extracellular polysaccharide from Chlorella vulgaris 224 was optimized by single factor and response surface methodology,and its antibacterial and antioxidant activity were studied.After optimization,the optimal conditions as follows:NaNO₃ 203.13 mg/L,NaCl 85.34 mg/L,NaHCO₃ 2.13 g/L.Under optimal conditions,the extracellular polysaccharide yield was 70.365 7 mg/L,which was 1.62 times higher than before optimization.The results showed that extracellular polysaccharide of C. vulgaris 224 had the highest antibacterial activity against Staphylococcus aureus and weak antimicrobial activity against Staphylococcus albus,Pseudomonas aeruginosa and Escherichia coli.At the same time,the extracellular polysaccharide of C. vulgaris 224 showed strong antioxidant activity.This study provided a certain reference value for screening natural antimicrobial and antioxidant active substances,and provided a theoretical basis for comprehensive utilization of oleaginous microalgae.

Key words: Chlorella vulgaris, extracellular polysaccharide, response surface methodology, antibacterial activity, antioxidant activity