Extraction, characterization and antioxidant activity evaluation of polysaccharides from Chlorella sp

Polysaccharides isolated from microalgae species have shown various biological properties. In this study, the response surface methodology (RSM) was applied to optimize the extraction conditions of crude polysaccharides from Chlorella by double enzymatic hydrolysis method (DEH). The systematic analysis of RSM revealed that the maximum yield of crude polysaccharides was obtained by adding 1.48% double enzymes (cellulose: papain = 1:1), controlling the hydrolysis temperature of 38.13 °C and pH of 5.34. Then, the crude polysaccharides were divided into three parts, named as F₁, F₂, and F₃, using a DEAE Sepharose FF column, and the molecular weights of F₁, F₂, and F₃ are 21.75 KDa, 1058 KDa, 5576 KDa, respectively. Monosaccharide composition analysis showed that the main constituents in F₁ and F₂ were Galactose (62.90% and 41.85%), while F₃ was commonly composed of 39.55% Arabinose and 32.33% Rhamnose. All polysaccharides contained characteristic absorption peaks of polysaccharides with functional groups (O-H, C-H, C = O), confirming that DEH did not affect the primary structural properties of polysaccharides. Furthermore, the Chlorella polysaccharides demonstrated good thermal stability below 180 °C and perfect antioxidant properties.