Alginate molecular mass produced by Azotobacter vinelandii in response to changes of the O2 transfer rate in chemostat cultures.

Alginate production by Azotobacter vinelandii growing in chemostat cultures was evaluated under different O(2) transfer rates (OTR). As a result of modifying the culture's agitation rate from 300 to 500 rpm, the OTR increased from 9 to 15.1 mmol l(-1) h(-1) and a slight variation in the alginate production (1.7-2.2 g l(-1)) was observed. At a constant growth rate (0.1 h(-1)), the mean molecular mass of the alginate was strongly influenced by changes in the OTR, varying from 860 to 1,690 kDa. These results support a possible relationship between alginate polymerization-depolymerization process and the O(2) uptake rate.