Alginate production by Pseudomonas aeruginosa and Azotobacter vinelatidii and the effect of alginate modifying enzymes on the structure of bacterial alginates was investigated. P. aeruginosa was demonstrated to be an unreliable producer of alginate. Acetyl contents were shown to vary depending on the growth conditions and guluronate blocks were not observed. P. aeruginosa was shown to possess extracellular activities for both an acetylating and a deacetylating enzyme. A radioassay was developed

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... and revealed that culture supematants (up to 2 days) were capable of incorporating radiolabeled sodium acetate into the alginate polymer. A dextran/polyethylene-glycol (PEG) 2-phase system was used to separate protein from alginate in supernatant fluid. After 6 days growth of P. aeruginosa R, the PEG phase upon separation was found to be capable of deacetylating alginate, indicating the presence of a deacetylase in this phase. It is suggested that an acetyl transferase is involved in a reversible acetylation process which can directly control the structural and physical properties of the polysaccharide. This investigation reports for the first time a strain of V. alginolyticus capable of degrading alginate as a sole source of carbon. Crude alginase activities were found both intracellulariy and extracellulariy and were partially characterised. The extracellular alginase did not appear to be substrate specific and was not affected by Ca++. The intracellular alginase favoured breakdown of G-block rather than M-block but in the presence of Ca++ there was equal substrate specificity. Stimulation of intracellular alginases by was also demonstrated for TABLE OF CONTENTS