Research On The Screening Of Extracellular Polysaccharide And The Bioactivity Of Natural Products

Firstly,the bacteria which can secrete extracellular polysaccharides were screened out and the structure and application of this extracellular polysaccharide were investigated.A new strain LX03 which produces exopolysaccharide was isolated from a soil sample,and it was determined to be a new species of Paenibacillus by the determination of its 16S rDNA sequence,denoted as Paenibacillus sp.LX03.The sequence of the strain was submitted to GenBank and the ID is KX503263.A preliminary analysis of the structure of LX03 was performed,and the result indicated that the extracellular polysaccharide LX03 was composed of three monosaccharides,including mannose,glucose and galactose,and the ratio was about 1:6:1.The special flocculation property of exopolysaccharide LX03 was also studied and it has potential to be applied to waste water treatment.Secondly,the biological activity especially the activity to relieve the cellular endoplasmic reticulum stress(ERS)of the natural products Salecan and piceatannol was investigated.The cell model of endoplasmic reticulum stress was induced by treating J774A.1 macrophages with thapsigargin(TG).Furthermore,the mouse model of ERS was established by treating mice with thapsigargin(TG)and tunicamycin(TM)to explore the effect of Salecan on endoplasmic reticulum stress.Our results indicated that Salecan could relieve ERS both in cells and mice by down-regulating the expression of key molecule CHOP,GRP78 and XBP1.Salecan can reduce the serum ALT and AST levels and attenuate the liver damage induced by intraperitoneal injection of TM in mice.Salecan also significantly decreased the mortality rate in TG-injected mice.These results suggest that Salecan could relive ER stress both in vitro and in vivo,and can also relieve the liver damage induced by ERS inducing chemicals.Last,we also studied the protective effect of piceatannol on acute liver injury induced by LPS/D-GalN in mice.The results show that piceatannol can reduce serum levels of AST and ALT,and effectively alleviate acute liver injury induced by LPS/D-GalN.This protective effect is related to the anti-inflammatory and antioxidant activity of piceatannol.In addition,the inhibitory effect of piceatannol on inflammation and ROS production induced by ERS inducer were further confirmed in cellular model.In this paper,a new type of extracellular polysaccharide LX03 was screened out and its potential application was studied.The protective effect of the natural products Salecan and piceatannol on endoplasmic reticulum stress were also investigated,and our results provide theoretical support for the future application of Salecan and piceatannol.