The biosynthesis and characterization of poly(β-hydroxyalkanoates) produced by Pseudomonas oleovorans

The biosynthesis of poly( beta -hydroxyalkanoates) (PHA's) by P. oleovorans was carried out by using the sodium salt of n-alkanoic acids as carbon sources. The PHA's produced contained at least two major (>5 mol %) monomer units. That is, depending on the carbon source used, the PHA's can have n-alkyl pendant groups with chain lengths from methyl to nonyl. Studies by differential scanning calorimetry and X-ray diffraction showed that the PHA's containing predominantly longer side chains (n-pentyl or greater) were crystalline polymers (T sub(m) from 45 to 61 degree C, delta H sub(m) up to 8.3 cal/g), whereas those which contained mostly n-propyl or n-butyl side chains showed little tendency to crystallize. The X-ray diffraction patterns of the longer side chain PHA's suggest that they crystallize with participation of both the main and side chains in a layered packing order.