Study On Extraction,purification And Modification Of Chlorella Polysaccharide

Chlorella vulgaris polysaccharide has good biological activity and can be applied to food,feed,chemical industry,energy,and the like,and has important research value.In this study,ultrasonic combined with hot water extraction was used to extract the intracellular crude polysaccharide of Chlorella vulgaris.The extraction conditions were optimized,and the crude polysaccharide was isolated and purified.The purified components were characterized and modified,and the results were as follows:1.Optimization of the extraction conditions of intracellular polysaccharides from Chlorella vulgaris.Through the single-factor test,PB test,climbing test,and response surface test,the best extraction protocol for the crude polysaccharide in Chlorella vulgaris was finally determined as follows: the mass fraction of NaOH was 2.0%,the material-to-liquid ratio was 1:25（g/mL）,the ultrasonic power was200 W,the ultrasonic time was 20 min,the extraction temperature was 80 ℃ and the extraction time was 1.5 h.Under these conditions,the extraction rate of crude polysaccharides was 18.086%.2.Isolation,purification,and structural characterization.Five polysaccharide components（CIP-1,CIP-2,CIP-3,CIP-4,and CIP-5）were obtained by eluting the intracellular crude polysaccharide of Chlorella with DEAE-52 cellulose column,while the component CIP-3,with the highest polysaccharide content and recovery,was eluted with Sephadex G-100 to obtain the purified component SCIP.SCIP was characterized by ultraviolet spectrum,Fourier transforms infrared spectrum,highperformance gel permeation chromatography,and ion chromatography,and it was found that SCIP was a pyranose containing uronic acid,and it was a uniform polysaccharide with a molecular weight of 9838 Da,which was mainly composed of glucose,rhamnose and galactose.3.Modification and antioxidant activity analysis.The SCIP was modified by sulfation,acetylation,and phosphorylation,and its modification conditions were optimized by single-factor and response surface methods.The antioxidant capacity of SCIP before and after modification was measured and its antioxidant activity was evaluated.The results showed that the antioxidant capacity of modified polysaccharides was more substantial than that of unmodified polysaccharides;the anti-DPPH radical results showed that phosphorylation had the strongest scavenging capacity for DPPH radicals at less than 5 mg/mL,and sulfation had the strongest scavenging capacity for DPPH radicals at more than 8 mg/mL,with a maximum scavenging rate of 93%;the anti-hydroxyl radical results showed that acetylation had the strongest antioxidant capacity against hydroxyl radicals and the maximum scavenging rate was 95% at a maximum concentration of 25 mg/mL.In this study,the optimal extraction conditions of intracellular crude polysaccharide from Chlorella were determined by response surface methodology,and SCIP was obtained by separation and purification.SCIP was characterized,chemically modified,and its antioxidant capacity was compared.The antioxidant capacity of polysaccharides was significantly improved.The research results provide a theoretical basis for the development of natural antioxidants,pharmaceuticals,and functional foods.