PRODUCTION OF EXTRACELLULAR POLYSACCHARIDES BY AZOTOBACTER-BEIJERINCKII

Azotobacter beijerinckii B-1615 forms extracellular polysaccharides (e xoglycans) only during active culture growth. Under batch-culture cond itions, the cell productivity is the same both when the carbon source (glucose) in the medium is limited and when it is present in excess. P hosphorus deficiency in the medium stimulates exoglycan formation. Inc reasing the aeration increases the polysaccharide yield only when A. b eijerinckii is cultured under conditions of nitrogen fixation. The opt imum pH of the medium for polysaccharide formation (9.0-10.0) is highe r than the optimum pH for maximum biomass production (8.0). At 20-degr ees-C A. beijerinckii grows more slowly but forms 2-3 times more exogl ycans than at 30-degrees-C.