Preparation And Properties Research Of The Exopolysaccharide From A Marine Pseudomonas PF-6

Microbial expolysaccharides are currently hotspots at present with excellent properties such as short-cycle, getting out of limit from season, growth areas and pest infection. They can be obtained by fermentation for industrialized production. In a word, they have a strong competitive power and a broad development prospect. Expolysaccharides from marine microbe with unique chemical structure and biological activity are widely used in marine ecology, microbiology, especially pharmic field.The main content of this paper was screening microorganisms producing EPS from marine environment, optimizing medium composition and ferment conditions, separating and purifying EPS. Properties of EPS were also evaluated to provide scientific evidences for the further research of exopolysaccharides. The main results were shown as following:1. The screened bacterium was primarily identified as Pseudomonas through analysis of physiological and biochemical properties. It was named Pseudomonas PF-6.2. By single factor and orthogonality experiments, the optimized medium composition was as follows:sucrose6.0%, yeast extract0.6%, NaCl3.0%, CaCl20.1%, K2HPO40.1%, KC10.05%, FeSO40.05%, initial pH7.0. The optimized ferment conditions were:250mL conical flask containing50mL liquid medium, inoculums size4%, temperature28℃, shaking speed160rpm. Under the optimized conditions, the yield of EPS could reach5.16g/L.3. EPS was extracted and purified by ethanol precipitation, sevage method, DEAE-52ion exchange, dialysis and freeze drying and obtained purified EPS. Ultraviolet scan spectrum analysis indicated that the EPS was absence of proteins and nucleic acids with no absorption at260nm or280nm. Infrared spectrometry of the EPS suggested that the EPS belonged to the β-type heteropolysaccharide with pyran group.4. Solubility, oil absorption, emulsibility, frothing, moisture absorption and moisture retention of EPS were studied in the research. The result indicated:EPS could dissolve in water but not in high concentration of organic solvent; EPS had good capacities of oil absorption, and NaCl and sucrose both had some effect on the capacities of oil absorption; EPS had some capacities of emulsibility and frothing, but lower than that of xanthan gum; In the environment of relative humidity43%and81%, capacity of moisture absorption of EPS was better than that of xanthan gum and oligosaccharides. In the environment of relative humidity43%, capacity of moisture retention of EPS was better than that of oligosaccharides, and capacities of moisture retention of EPS and oligosaccharides were almost the same in the environment of silica gel.5. The antioxidative activity of EPS indicated:EPS had some reducing power and scavenging action on 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 IC50of Vc were0.617mg/mL and0.147mg/mL to-OH and O2-· respectively. The IC50of the EPS were0.341mg/mL and0.149mg/mL under the same condition. The work would confirm that EPS had strong potential as a natural antioxidant applied to food, healthcare, cosmetics and other fields.