Archaeal Production of Polyhydroxyalkanoate (PHA) Co- and Terpolyesters from Biodiesel Industry-Derived By-Products

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. 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, indicating the feasibility of applying CGP as feedstock. Analysis of molar mass distribution revealed a weight average molar mass M w of 150 kDa and polydispersity P i of 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 γ-butyrolactone as 4-hydroxybutyrate (4HB) precursor resulted in a poly[(R)-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 (2.5°C), increased molar mass (391 kDa), and a polydispersity similar to the copolyesters.

Start a Research on Biopolymer Polyhydroxyalkanoate (PHA): A Review

“…Haloarchaea are the extremely halophilic members of the archaea domain, which require high salt concentrations for normal enzyme activity, growing at saturation conditions of up to 6 M NaCl [113]. Haloarchaea have been reported to synthesize PHA from glucose, volatile fatty acids and more complex carbon sources such as starch, whey hydrolysate, vinasse and crude glycerol from biodiesel production [92][93][94][95]. The type of PHA synthesized appeared to be exclusively scl-PHA homopolymer containing either 3HB or 3HV monomers, and/or scl-PHA heteropolymer containing both 3HB and 3HV monomers [42,95].…”

“…At present, the best PHA producer is Haloferax mediterranei (DSM 1411), which requires 2 to 5 M NaCl for growth and can accumulate high PHA levels between 50 and 76 %CDM [92][93][94].…”

Biocompounds from Haloarchaea and Their Uses in Biotechnology

“…Cheap carbon sources such as glycerol [89,90], rice bran [91], rice-based ethanol stillage [92], cheese whey [93], and olive mill wastewater (the effluent of the olive oil industry) have been tested using multistage processes [94,95] or only one-stage process ( …”

Synthetic routes to degradable copolymers deriving from the biosynthesized polyhydroxyalkanoates: A mini review

“…Varying the copolymer composition affords obtaining copolyesters with adjustable mechanical and processing properties exceeding those of the P3HB homopolymer. Terpolyesters poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [25][26][27], poly(3-hydroxybutyrateco-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HVHHx) [28,29] and poly(3-hydroxybutyrate-co-4-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB4HBHHx) [30,31] have be synthesized by changing the feedstock and microorganisms. Natural blocky-structured PHAs have been successfully synthesized in vivo by microorganisms and in vitro.…”