Fed-Batch Synthesis of Poly(3-Hydroxybutyrate) and Poly(3-Hydroxybutyrate-co-4-Hydroxybutyrate) from Sucrose and 4-Hydroxybutyrate Precursors by Burkholderia sacchari Strain DSM 17165

Miguel Miranda De Sousa Dias; Martin Koller; Dario Puppi; Andrea Morelli; Federica Chiellini; Gerhart Braunegg

doi:10.3390/bioengineering4020036

Fed-Batch Synthesis of Poly(3-Hydroxybutyrate) and Poly(3-Hydroxybutyrate-co-4-Hydroxybutyrate) from Sucrose and 4-Hydroxybutyrate Precursors by Burkholderia sacchari Strain DSM 17165

Bioengineering (Basel). 2017 Apr 20;4(2):36. doi: 10.3390/bioengineering4020036.

Authors

Miguel Miranda De Sousa Dias¹, Martin Koller^{2

3}, Dario Puppi⁴, Andrea Morelli⁵, Federica Chiellini⁶, Gerhart Braunegg⁷

Affiliations

¹ Université Pierre et Marie Curie UPMC, Institut national de la santé et de la recherche médicale INSERM, Centre national de la recherche scientifique CNRS, Institut de la Vision, Sorbonne Universités, 17 rue Moreau, 75012 Paris 06, France. migueldias670@hotmail.com.
² Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28/III, 8010 Graz, Austria. martin.koller@uni-graz.at.
³ ARENA-Association for Resource Efficient and Sustainable Technologies, Inffeldgasse 21b, 8010 Graz, Austria. martin.koller@uni-graz.at.
⁴ BIOLab Research Group, Department of Chemistry & Industrial Chemistry, University of Pisa, UdR INSTM Pisa, Via Moruzzi, 13, 56124 Pisa, Italy. d.puppi@dcci.unipi.it.
⁵ BIOLab Research Group, Department of Chemistry & Industrial Chemistry, University of Pisa, UdR INSTM Pisa, Via Moruzzi, 13, 56124 Pisa, Italy. a.morelli@dcci.unipi.it.
⁶ BIOLab Research Group, Department of Chemistry & Industrial Chemistry, University of Pisa, UdR INSTM Pisa, Via Moruzzi, 13, 56124 Pisa, Italy. federica.chiellini@unipi.it.
⁷ ARENA-Association for Resource Efficient and Sustainable Technologies, Inffeldgasse 21b, 8010 Graz, Austria. g.braunegg@tugraz.at.

Abstract

Based on direct sucrose conversion, the bacterium Burkholderia sacchari is an excellent producer of the microbial homopolyester poly(3-hydroxybutyrate) (PHB). Restrictions of the strain's wild type in metabolizing structurally related 3-hydroxyvalerate (3HV) precursors towards 3HV-containing polyhydroxyalkanoate (PHA) copolyester calls for alternatives. We demonstrate the highly productive biosynthesis of PHA copolyesters consisting of 3-hydroxybuytrate (3HB) and 4-hydroxybutyrate (4HB) monomers. Controlled bioreactor cultivations were carried out using saccharose from the Brazilian sugarcane industry as the main carbon source, with and without co-feeding with the 4HB-related precursor γ-butyrolactone (GBL). Without GBL co-feeding, the homopolyester PHB was produced at a volumetric productivity of 1.29 g/(L•h), a mass fraction of 0.52 g PHB per g biomass, and a final PHB concentration of 36.5 g/L; the maximum specific growth rate µmax amounted to 0.15 1/h. Adding GBL, we obtained 3HB and 4HB monomers in the polyester at a volumetric productivity of 1.87 g/(L•h), a mass fraction of 0.72 g PHA per g biomass, a final PHA concentration of 53.7 g/L, and a µmax of 0.18 1/h. Thermoanalysis revealed improved material properties of the second polyester in terms of reduced melting temperature Tm (161 °C vs. 178 °C) and decreased degree of crystallinity Xc (24% vs. 71%), indicating its enhanced suitability for polymer processing.

Keywords: 4-hydroxybutyrate; Burkholderia sacchari; biopolymers; copolyester; poly(3-hydroxybutyrate-co-4-hydroxybutyrate); polyhydroxyalkanoate (PHA); saccharose; sucrose; sugarcane.