Isolation And Antioxidant Characteristic Research Of The Compound Of Protein And Exopolysaccharides From Marine Pseudomonas PT-8

Soy protein exhibits broad sources and low price. Recently, it was greatly cared because of its high nutritional value and unique features of health care. However, its functional properties such as inoxidability, solubility and heat stability were poor. The application of soy protein restricted in the food industry. Because of the special environment, the synthetic process of polysaccharides in the marine microorganisms is different from the land dwellers. The marine microorganisms have the potential to produce extracellular polysaccharides with new structure and activity. Usage of marine microbial polysaccharide graft soy protein to improve soy protein functional properties such as antioxidant; it is of great significance in theory and practice to expand application area of modification of soy protein and natural antioxidants.The main contents of this paper were as following; Screen microorganisms producing extracellular polysaccharides (EPS) in marine conditions. Optimize culture conditions, Separate and purify EPS. Study on antioxidant properties of EPS. In this paper, soy protein isolate (SPI), mairine micro-exopolysaccharides were used as the starting materials, and EPS-SPI grafts were synthesized by dry heating.The conditions, antioxidation and other functional properties of conjugates were studied.The bacterium in this study was screened out from the sea mew and identified as Pseudomonas by physiological and biochemical characteristic analysis. It was named Pseudomonas PT-8.The optimal culture medium was as follows:3.5%sucrose,2%beef extract, sodium chloride5.5%, K2HPO40.1%, MgSO40.1%, KH2SP40.05%, MnSO40.05%and initial pH7.5. By single factor experiments:temperature30℃, inoculums size4%, rotatory speed160rpm. The yield of PT-8was5.7g/L.The antioxidation of EPS indicates:the EPS had strong reducing power and good scavenging ability to the DPPH-, especially had strong scavenging action on-OH and-O2-compared with Vc.The scavenging activity to-OH and-O2-was represented by the content scavenged50%of all radicals (IC50).The IC50to·OH and·O2-of Vc were0.312mg/mL and0.141mg/mL to·OH and·O2-respectively. The IC50of the EPS were0.161mg/mL and0.128mg/mL under the same condition.The dry-heating conditions of EPS-SPI graft reaction were studied. According to the degree of graft (DG), suitable conditions were optimized by response surface methodology (RSM). EPS/SPI(w/w)3.15, reaction temperature62℃and heating time48h were optimum conditions for the preparation of the EPI-SPI grafts. Under these conditions the degree of glycation reached up to51.8%.The study found that the heat stability of the grafted product was improved about10%. The antioxidative activity of MRPs indicated:The scavenging of grafted product on·OH and·O2-is four times than that of SPI. The scavenging of grafted product on DPPH·improved1time than that of SPI.The antioxidant activities of MRPs increased with increases in its concentration.