Studies On Screening And Determinating Of Sphingomonas Paucimobilis And Its Exopolysaccharide

This paper is concerned about Sphingomonas paucimobilis and its exopolysaccharide (EPS) , including screening and determination of strain , the product process of EPS , studies of bacterial morphology and secretion of EPS by electron microscope , kinetics of fermentation , UV mutants and effect of antibiotics on secreting of EPS , extraction ,purity and structural studies of EPS , rheology of EPS . Important aspects and results are as follows :1. A bacterium S₁ secreting exopolysaccharides is screened out from water samples . Systematic tests indicate that it is Sphingomonas paucimobilis :Strain of S₁ is a gram-negative , nonsporeforming , rod-shape bacterium with single polar flagella . The size of cell is about 1.4 × 0.7μm . Circular, low convex , smooth , opaque , mucoid and yellow colonies appear on nutrient agar after 48 hours . Kovacs oxidas and catalase are positive . Arginine dihydrolase , lysine decarboxylase and orinithine decarboxylase are negetive . Nitrate is not reduced to nitrite . Urease and gelatinase are negative . ONPG , Esculin and Tween 80 are hydrolyzed . Nonfermentation . Organism is not capable of growth at 42℃ . The strain is susceptible to the antibiotics of erythromycin , chlortetracycline, penicillin and ampicilin but not kanamycin and streptomycin .2 Fermentation process of EPS by Sphingomonas paucimobilis S₁ is two-step fermentation . Two phase can be distinguished . The medium composition and process condition are described as follows :Phase one : Sucrose 10 g/L NH₄NO₃ 0.5 g/L KH₂PO₄ 0.5 g/L MnSO₄ 0.3 g/L MgSO₄ 0.1 g/ L Tween 80 0.02 g/L . pH value is 7.2 , and temperature is 33 35 ℃ .Phase two : Addition of 40g/L sucrose after 16 hours . pH value is adjusted to 6.5 , temperature to 24 25 °C. Fermentation time is 72 hours .3 Electron micrographs of Sphingomonas paucimobilis S₁ show that organisms begin to produce EPS when bacterial body become longer .With development of fermentation (>24 hours ) , more and more poly-β-hydroxybutyrates are accumulated . When fermentation time is 76 hours , poly-β-hydroxybutyrates...