Physiological Activity Of Porphyridium Purpureum Polysaccharide And Analysis Of Gene Families Related To Polysaccharide Synthesis And Metabolomics

Porphyridium purpureum is a kind of single-cell red algae that can adapt to high-salt environment.During its growth,it can synthesize a variety of bioactive substances and has a good development prospect.Porphyridium purpureum polysaccharide is one of the most important research directions.As one of the important environmental factors,salinity can affect the growth of Porphyridium purpureum,and also affect the production of many metabolites of Porphyridium purpureum,including bioactive substances.At present,the effect of salinity on the growth of Porphyridium purpureum had been studied,but the effect of salinity on the polysaccharide synthesis of Porphyridium purpureum had not been systematically and accurately explored.In this study,four different salinity levels（0ppt,17 ppt,34 ppt,68 ppt）were set up to culture Porphyridium purpureum and extract its polysaccharides,and the physical and chemical properties,in vitro antioxidant properties,in vitro hypoglycemic properties and hypolipidemic properties of the four polysaccharides were measured to explore the effects of salinity on the physiological activities of Porphyridium purpureum polysaccharides.The phylogenetic analysis of the gene families related to polysaccharide synthesis of Porphyridium purpureum and the metabolomics analysis of Porphyridium purpureum under high salt stress were also carried out.The main results were as follows:（1）The molecular weight of Porphyridium purpureum polysaccharide obtained under the four salinity conditions of 0 ppt,17 ppt,34 ppt and 68 ppt was different,and the monosaccharide composition was slightly different.The content of polysaccharide was5.45%,10.33%,8.54%and 6.11%by phenol-sulfuric acid method.In addition to the polysaccharides obtained at 68 ppt,the monosaccharide components in the other three polysaccharides accounted for the first three were xylose,galactose and glucose,68 ppt contained galactose,galacturonic acid and xylose.The molecular configurations may be irregularly linear.The polysaccharide of Porphyridium purpureum at 17 ppt was purified and determined to contain two components.The infrared spectrum analysis showed that it had pyranose ring andβ-Glycoside bond.（2）The Porphyridium purpureum polysaccharide obtained under the four salinity conditions of 0 ppt,17 ppt,34 ppt,and 68 ppt showed certain effects on antioxidation,hypoglycemic and hypolipidemic in vitro,and all showed the characteristics of17>34>68>0,that was,the polysaccharide obtained under the condition of 17 ppt had the best performance,and the polysaccharide obtained under the condition of 0 ppt was the worst.The free radicals scavenging rate of polysaccharide at 17 ppt on DPPH,·OH and O^2-were 37.46%,32.40%and 25.65%respectively.The inhibition rate ofα-Glucosidase andα-amylase were 12%and 20%respectively.The inhibition rates of pancreatic lipase and cholesterol esterase were 30.31%and 24.90%respectively,and the binding rates of sodium taurocholate and sodium glycine cholate were 74.96%and 67.45%respectively.（3）Four gene families related to polysaccharide synthesis of Porphyridium purpureum were identified and screened,namely GH,GT,CBM and CE.The GH family consisted of 32 members.The GT family consisted of 135 members.The CBM family included 36 members.The CE family consisted of 11 members.（4）The analysis results based on quasi-targeted metabolomics showed that under the two different salinity conditions of 0 ppt and 68 ppt,the metabolites in the Porphyridium purpureum treated with high salt（68 ppt）stress increased,carbohydrates and its derivatives showed up-regulated expression on the whole,and enriched into three carbohydrate metabolic pathways.These metabolites and metabolic pathways may be involved in the response process of Porphyridium purpureum to high salt stress.