Production of polyhydroxyalkanoates byAzotobacter vinelandii UWD in beet molasses culture

Beet molasses (BM) has proven to be an excel-lent feedstock for polyhydroxyalkanoate (PHA) production by Azotobacter vinelandii UWD. The substrate-cost for PHA production from BM in fed-batch culture was one-third of that using glu-cose. Copolymers containing /3-hydroxyvalerate are readily formed in BM medium when valerate is used as a precursor. The origin of the hydroxy-valerate monomer was most likely a /3-ketoacyl-CoA intermediate in the /3-oxidation of odd-length n-alkanoates. BM also contained unidenti-fied factors that stimulated PHA production to a greater extent han cell growth. Analysis of BM fractions has suggested that amino-N compounds may be required for PHA-yield-promotion. Thus the addition of a small amount of commercial peptone to mineral salts medium containing pure or other impure sugar sources has led to signifi-cantly increased PHA yields