Burkholderia sp. F24, originally isolated from soil, was capable of growth on xylose and removed organic inhibitors present in a hemicellulosic hydrolysate and simultaneously produced poly-3-hydroxybutyrate (P3HB). Using non-detoxified hydrolysate, Burkholderia sp. F24 reached a cell dry weight (CDW) of 6.8 g L(-1), containing 48 % of P3HB and exhibited a volumetric productivity (PP3HB) of 0.10 g L(-1) h(-1). Poly-3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (P3HB-co-3HV) were produced using xylose and levulinic acid (LA) as carbon sources. In shake flask cultures, the 3HV content in the copolymer increased from 9 to 43 mol% by adding LA from 1.0 to 5.0 g L(-1). In high cell density cultivation using concentrated hemicellulosic hydrolysate F24 reached 25.04 g L(-1) of CDW containing 49 % of P3HB and PP3HB of 0.28 g L(-1 )h(-1). Based on these findings, second-generation ethanol and bioplastics from sugarcane bagasse is proposed.

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Aim: Evaluation of the capability of Burkholderia sacchari to incorporate different monomers into polyhydroxyalkanoates (PHA). Methods and Results: Thirty different carbon sources were evaluated as cosubstrates for B. sacchari growing on glucose with the intention to promote the incorporation of different monomers into the PHA produced by this species. With odd-numbered fatty acids, incorporation of the 3HV monomer was achieved, up to 65 mol% in the case of valerate. With 4-hydroxybutyrate, incorporation of 4HB was obtained, representing 9Á1 mol%. With hexanoic acid, the production of P3HB-co-3HHx was achieved, containing up to 1Á6 mol% of 3HHx. The molar fraction of 3HHx was found to be dependent on the ratio of glucose to hexanoic acid supplied. Metabolic flux analysis revealed a high efficiency of B. sacchari in converting carbon sources into P3HB-co-3HHx. Nevertheless, hexanoic acid was only poorly converted to 3HHx. Conclusions: Burkholderia sacchari is able to incorporate 3HV, 4HB and 3HHx in PHA containing mainly 3HB. The 3HHx content of P3HB-co-3HHx can be controlled by varying the glucose to hexanoic acid ratio. Burkholderia sacchari is highly efficient in converting carbon sources into PHA; however, only 2% of the hexanoic acid supplied could be converted to 3HHx. Significance and Impact of the Study: This is the first report describing an approach to modulate the composition of P3HB-co-3HHx produced by bacteria using mixtures of carbohydrate and hexanoic acid as carbon source.

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