Manipulation and Characterization of Alginate Exo polysaccharides produced by Azotobacter Vinelandii

Exo polysaccharides (EPS) have been found in a wide range of applications in food industry and in the biomedical field. In the present study, the effect of nutritional factors (carbon and nitrogen sources) and gamma irradiations on alginate production by Azotobacter vinelandii was investigated. To understand the direct and indirect relations among these variables, a two way factorial design experiment was set up. At low concentration of carbon source (≤ 20 g/l), the alginate yield was influenced by the type of nitrogen substrate and C/N ratio, whereas the role of these factors on alginate production was minimized at high concentration of carbon source (> 20 g/l). Batch fermentation of alginate exo polysaccharides was manipulated by maintaining the ph value of the cultures at 7 along the incubation period and reducing the agitation speed to 100 rpm after 24 h at the time of inoculation. This process succeeded to increase the alginate yield exponentially with time by 50%. Exposing A. vinelandii cells to gamma irradiation at dose level 0.5 kGy decreased their activity to synthesis alginate by 44%. The produced alginate was characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and differential scanning calorimeter (DSC).