Abstract: The solution viscosity of a polysaccharide, microbial alginate, produced by culturing strains of Azotobacter vinelandii, is controlled by addition of a protease to the culture broth. The protease can be added during the culture, to obtain a polysaccharide of increased viscosity. Alternatively or additionally protease can also be added after culture but before the polysaccharide is isolated from the broth, for example, to prevent reduction of viscosity during storage. Neutral and alkaline proteases having activity at around pH 7 are particularly suitable.

Abstract: Polysaccharide is produced in high yields by continuous culture of a polysaccharide-producing strain of Azotobacter vinelandii under phosphate-limited conditions, preferably with restricted oxygen uptake.

Abstract: Polysaccharide is produced in good yields with good control by continuous culture of a polysaccharide-producing strain of Azotobacter vinelandii under carbon-limited conditions, preferably with restricted oxygen uptake, with the advantage that the effluents produced are non-polluting having a low biological oxygen demand (B.O.D.).