Liquefied Wood as Inexpensive Precursor-Feedstock for Bio-Mediated Incorporation of (R)-3-Hydroxyvalerate into Polyhydroxyalkanoates

Martin Koller; Miguel Miranda de Sousa Dias; Alejandra Rodríguez-Contreras; Matjaž Kunaver; Ema Žagar; Andrej Kržan; Gerhart Braunegg

doi:10.3390/ma8095321

Liquefied Wood as Inexpensive Precursor-Feedstock for Bio-Mediated Incorporation of (R)-3-Hydroxyvalerate into Polyhydroxyalkanoates

Materials (Basel). 2015 Sep 23;8(9):6543-6557. doi: 10.3390/ma8095321.

Authors

Martin Koller^{1

2}, Miguel Miranda de Sousa Dias³, Alejandra Rodríguez-Contreras⁴, Matjaž Kunaver⁵, Ema Žagar⁶, Andrej Kržan⁷, Gerhart Braunegg⁸

Affiliations

¹ Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28/III, Graz 8010, Austria. martin.koller@uni-graz.at.
² ARENA-Association for resource efficient and sustainable technologies, Inffeldgasse 23, Graz 8010, Austria. martin.koller@uni-graz.at.
³ Department of Genetics, Institut de la Vision, 17 rue Moreau, 75012 Paris, France. miguel.dias@inserm.fr.
⁴ Departament d'Òptica i Optometria, Universitat Politècnica de Catalunya Barcelona Tech, Sant Nebridi 22, 08222 Terrassa, Barcelona, Spain. sandra8855@hotmail.com.
⁵ Laboratory for Polymer Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia. matjaz.kunaver@ki.si.
⁶ Laboratory for Polymer Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia. ema.zagar@ki.si.
⁷ Laboratory for Polymer Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia. andrej.krzan@ki.si.
⁸ ARENA-Association for resource efficient and sustainable technologies, Inffeldgasse 23, Graz 8010, Austria. g.braunegg@tugraz.at.

Abstract

Liquefied wood (LW) prepared in a microwave process was applied as a novel; inexpensive precursor feedstock for incorporation of (R)-3-hydroxyvalerate (3HV) into polyhydroxyalkanoate (PHA) biopolyesters in order to improve the biopolyester's material quality; Cupriavidus necator was applied as microbial production strain. For proof of concept, pre-experiments were carried out on a shake flask scale using different mixtures of glucose and LW as carbon source. The results indicate that LW definitely acts as a 3HV precursor, but, at the same time, displays toxic effects on C. necator at concentrations exceeding 10 g/L. Based on these findings, PHA biosynthesis under controlled conditions was performed using a fed-batch feeding regime on a bioreactor scale. As major outcome, a poly(3HB-co-0.8%-3HV) copolyester was obtained displaying a desired high molar mass of M_w = 5.39 × 10⁵ g/mol at low molar-mass dispersity (Đ_M of 1.53), a degree of crystallinity (X_c) of 62.1%, and melting temperature T_m (176.3 °C) slightly lower than values reported for poly([R]-3-hydroxybutyrate) (PHB) homopolyester produced by C. necator; thus, the produced biopolyester is expected to be more suitable for polymer processing purposes.

Keywords: (R)-3-Hydroxyvalerate (3HV); biopolymers; copolyester; liquefied wood; polyhydroxyalkanoates (PHA); precursor substrates.