THE EFFECT OF SUBSTRATE ON THE MOLECULAR-WEIGHT OF POLY-BETA-HYDROXYBUTYRATE PRODUCED BY AZOTOBACTER-VINELANDII UWD

Azotobacter vinelandii UWD produced very high molecular weight (MW) (a pprox. 4 million Daltons) poly-beta-hydroxybutyrate (PHB) when grown i n 5% w/v beet molasses medium. The polymer MW decreased as the beet mo lasses concentration was increased. Similar results were obtained in e quivalent concentrations of sucrose (as raw sugar), but the polymer MW was not greater than 1.6 million. This difference was not caused by m ore severe oxygen-limitation in the beet molasses medium. It appeared that the non-sugar components of beet molasses promoted the formation of higher MW polymer. Fish peptone, a known PHB-yield-promoter in this organism, did not promote the formation of very high MW polymer.