Continuous cultures for alginate production from Azotobacter vinelandii were conducted at different specific oxygen uptake rates (q o2 ) under oxygen-limited conditions. As a result of varying the agitation rate, the q o2 increased from 2.2 to 6.0mmolg −1 h −1 . An increase in q o2 up to 4.8mmolg −1 h −1 resulted in an increase of alginate concentration, as well as in the specific alginate production rate, which can be attributed to that carbon flux was less diverted towards biomass production. A lower alginate molecular weight (869kDa as compared to 1350kDa) was obtained by increasing the q o2 from 2.2 to 4.8mmolg −1 h −1 and a higher gene expression of algL (about 8-fold) was observed, which could explain the decrease in the alginate molecular weight. The results showed for the first time that alginate production and carbon distribution are affected by the q o2 . The manipulation of this parameter could be used as a control strategy for alginate production.