Production of poly-beta-hydroxybutyrate by Azotobacter vinelandii in a two-stage fermentation process

Poly-beta-hydroxybutyrate (PHB) production in Azotobacter vinelandii UWD, a mutant that produces PHB constitutively, was suppressed by high aeration of beet molasses medium. Thus a two-stage process was designed using aeration to promote growth and suppress PHB production in the first phase, while fewer aeration of raw sugar medium containing fish peptone was used to promote PHB formation in the second phase. A PHB yield of 36 g/l and productivity of >1 g polymer l(-1).h was obtained by this approach.