Burkholderia sacchari was used to produce poly-3-hydroxybutyrate-co-3-hydroxyvalerate block copolymers from xylose and levulinic acid. Levulinic acid was the preferred substrate resulting in 3-hydroxyvalerate (3HV) contents as high as 95 mol% at 24 h. The 3HB:3HV ratios were controlled by the initial levulinic acid media concentration and fermentation length. Higher levulinic acid concentrations and longer durations, resulted in polymers with two glass transition temperatures, each approximating those associated with poly-3HB and poly-3HV. 13C NMR confirmed the presence of high concentrations of 3HB-3HB and 3HV-3HV homopolymeric dyads, while mass spectrometry of the partial hydrolysis products did not conform to Bernoullian statistics for randomness, confirming block sequences. MS/MS analysis of specific oligomers showed the mass-loss of 86 amu (a 3HB unit) and 100 amu (a 3HV unit) attesting to some randomness within the polymers. This study verifies the potential for producing Poly-3HB-block-3HV copolymers from inexpensive biorenewable feedstocks without sequential addition of carbon sources.
Keywords: Burkholderia sacchari; Levulinic acid; Poly-3-hydroxybutyrate-block-3-hydroxyvalerate; Xylose.
Published by Elsevier Ltd.