Alginic acid Azotobacter vinelandii

Formation of L-guluronic acid, a component of the alginic acid-like polysaccharide produced by P. aeruginosa and Azotobacter vinelandii, requires special comment. In this case, a polymer built from /3-(l- 4)-linked D-mannosyluronic acid residues serves as an intermediate in the biosynthesis.204,205 Part of the D-mannosyluronic acid residues in the polymer is subjected to an epimerization at C-5 catalyzed by an exocellular enzyme of the micro-organism,205-207 producing a polysaccharide composed of structural blocks that contain only D-mannosyluronic acid or only l-gulosyluronic acid residues, as well %s some having both. The mechanism of the epimerization remains unclear. 

The biosynthesis of alginic acid [69, 243, 244] has been investigated in both seaweeds and bacteria. Azotobacter vinelandii produces exopolysaccharide in a high carbon-low nitrogen environment and hexoses, disaccharides and D-mannitol can all provide a carbon source. This bacterium contains enzymes that convert hexose phosphates into GDPMan (reactions A to D and J) which then undergoes oxidation and polymerisation... 

Materials. Alginic acid (sample S-35) produced by Azotobacter vinelandii (1) was a kind gift of Dr.K.C.Symes, Tate and Lyle... 

Pindar, D. R, Bucke, C. The biosynthesis of alginic acid by Azotobacter vinelandii. J Biochem 1975,152, 617-622. 

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