Characterization of new bacterial copolyesters containing 3-hydroxyoxoalkanoates and acetoxy-3-hydroxyalkanoates

Two novel bacterial poly(3-hydroxyalkanoates) (PHAs) with either 3-hydroxy-7-oxooctanoate (HOO) and 3-hydroxy-5-oxohexanoate (HOH) or 8-acetoxy-3-hydroxyoctanoate (AHO), 6-acetoxy-3-hydroxyhexanoate (AHH), and 4-acetoxy-3-hydroxybutyrate (AHB) monomer units were produced at pilot scale. For the biosynthesis of these PHAs Pseudomonas oleovorans was cultivated at a 24 L scale in two-liquid-phase fed-batch processes using mineral salts medium and mixtures of 2-octanone/octane or n-octylacetate/octane as carbon sources. The bacterial accumulation of the polyesters was induced by nitrogen starvation and the addition of the substrate mixtures. Under these conditions, 26 and 45 g of PKA were isolated. The PHAs contained 10.3 and 3.3 mol % of oxo and acetoxy group monomers. Physical characterization was done with respect to their molecular weights, and thermal properties and similar results were found as for octane-based PHA. All monomer units have been identified by 2D H-1 and C-13 heteronuclear correlated NMR spectroscopy (HSQC, HMBC, and HSQC-TOCSY), and the composition of the copolyesters was quantified from H-1 NMR spectra.