• Muhr, Alexander
• Fasl, Hubert
• Braunegg, Gerhart
• Stelzer, Franz
• Hermann-Krauss, Carmen
• Koller, Martin

Abstract

The archaeon Haloferax mediterranei was selected for production of PHA co- and terpolyesters using inexpensive crude glycerol phase (CGP) from biodiesel production as carbon source. CGP was assessed by comparison with the application of pure glycerol.<br/>Applying pure glycerol, a copolyester with a molar fraction of 3-hydroxybutyrate (3HB) of 0.90 mol/mol and 3-hydroxyvalerate (3HV) of 0.10 mol/mol, was produced at a volumetric productivity of 0.12 g/Lh and an intracellular PHA content of 75.4 wt.-% in the sum of biomass protein plus PHA. Application of CGP resulted in the same polyester composition and volumetric productivity,<br/>indicating the feasibility of applying CGP as feedstock. Analysis of molar mass distribution revealed a weight average molar mass of 150 kDa and polydispersityof 2.1 for pure glycerol and 253 kDa and 2.7 for CGP, respectively; melting temperatures ranged between 130 and 140∘C in both setups. Supplying -butyrolactone as 4-hydroxybutyrate (4HB) precursor resulted in a poly[(R)-<br/>3-hydroxybutyrate-co-(R)-3-hydroxyvalerate-co-4-hydroxybutyrate] (PHBHV4HB) terpolyester containing 3HV (0.12 mol/mol) and 4HB (0.05 mol/mol) in the poly[(R)-3-hydroxybutyrate] (PHB) matrix; in addition, this process runs without sterilization of the bioreactor. The terpolyester displayed reduced melting (melting endotherms at 122 and 137∘C) and glass transition temperature<br/>(2.5∘C), increased molar mass (391 kDa), and a polydispersity similar to the copolyesters.

Topics

• Carbon
• phase
• glass
• glass
• glass transition temperature
• polydispersity
• melting temperature