Abstract

Polyhydroxyalkanoates (PHAs) are well known biobased thermoplastic polyesters. PHAs are mainly produced by bacterial cultures from sugars or vegetal oils. Many types of PHAs exhibit thermal and mechanical properties similar to polypropylene. Burkholderia xenovorans LB400 is a model bacterium for the degradation of polychlorobiphenyls and aromatic compounds. The aim of this study is to evaluate if B. xenovorans LB400 is able to synthesize poly(3-hydroxibutyrate) [P(3HB], and poly(3-hydroxybutirate-co-3-hydroxyvalerate) [P(3HB-co-3HV] using different sugars sources such as glucose, xylose, gluconate and mixture of these sugars with valerate as sole carbon source under nitrogen limiting conditions. The propylesters were extracted with organic solvents and analysed by gas chromatography coupled with a mass spectrometer (GC-MS). This analysis indicated the presence of P(3HB) in cells grown on glucose, xylose and gluconate as sole carbon source and nitrogen-limiting conditions. Strain LB400 produces P(3HB-co-3HV) during growth on a mixture glucose/valerate or xylose/valerate as sole carbon source and nitrogen limitation conditions. PHAs production by B. xenovorans LB400 was quantified. The molecular and physicochemical properties of P(3HB-co-3HV) produced by strain LB400 were determined. These polymers were extracted using chloroform. P(3HB-co-3HV) was analysed by infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and differential scanning calorimetry (DSC). Increasing the concentration of xylose and nitrogen, higher biomass was obtained and the production of P(3HB) was enhanced. Xylose is a sugar released by hydrolysis from hemicellulose, which is available in high amounts as by-products of forestry. Therefore, PHA production by B. xenovorans LB400 using xylose as carbon source is an attractive strategy.