Preparation And Application Research Of Microbial Polysaccharides

Microbial exopolysaccharides with stable structure, inexpensive price, short-cycle and good performance have extensive applications in the industries of food, medicine, chemical and petroleum. It is of great significance in theory and practice to improve the market competing capacity and expand application area.The main contents of this paper were as following:1. Screen microorganisms producing EPS, optimize culture conditions.2. Separate and purify EPS.3. Study on properties and application of EPS.The bacterium in this thesis was screened out from the soil and identified as Arthrobacter by physiological and biochemical characteristic analysis. It was named Arthrobacter ps-5.Orthogonal test of3factors,3levels based on single factor experiments was designed to increase EPS of Arthrobacter ps-5according to response surface methodology (RSM). The optimal culture medium was as follows (g/L):sucrose20.96, yeast extract25.35, beef extract3.0, K2HPO41.98, CaCl20.5, MnSO40.5. The optimal culture conditions were250mL conical flask containing50mL liquid medium, initial pH6.0-7.0, temperature28℃, inoculums size4%, rotatory speed160rpm by single factor experiments.Under the optimized conditions, the yield of EPS was5.48g/L.There were four methods to remove proteins from EPS. The results showed that EPS removed proteins by combined methods of enzymatic and Sevag were best. The rate of deproteinization was72%and the rate of losing polysaccharides was21%in such condition.The effects of EPS on oxidation resistance, hygroscopisity and moisture rerention were studied. The results showed that EPS had strong reductive ability, antioxidative activity, and eliminated effect on the·OH and O2-·. EPS had higher hydroscopicity in relative humidity (RH) of81%and43%, but lower moisture rerention in RH of43%and0%(silica-gel). The results indicated that EPS had good hydroscopicity and moisture retention. EPS had antioxidant activity on lard and sesame oil, which could effectively delay the auto-oxidation process of oil. The antioxidation increased with the increasing of EPS concentration (0.05%<0.1%), but it hadn’t obvious dose-effect relationship. And the effect of antioxidantion of this EPS on animal fat was better than vegetable oil.