Effects of Carbon Source and Inorganic Phosphate Concentration on the Production of Alginic Acid by a Mutant of Azotobacter vinelandii and on the Enzymes Involved in its Biosynthesis

Abstract

The specific activities of the key enzymes involved in the biosynthesis of the exopolysaccharide alginic acid by Azotobacter vinelandii were determined in extracts of batchcultured organisms grown with different carbon sources in the presence of limited and excess inorganic phosphate. Alginic acid production was also measured. Glucose, fructose, sorbitol, mannitol, glycerol and gluconate resembled sucrose in supporting much greater alginate production in media containing growth-limiting amounts of inorganic phosphate. Mannose supported only poor growth with no alginate formation, and growth did not occur on acetate. Increases in the specific activities of phosphomannose isomerase, GDPmannose pyrophosphorylase and GDPmannose dehydrogenase were accompanied by increased alginic acid production. Our results accord with the suggestion that alginate formation is controlled by derepression of key biosynthetic enzymes.