%0 Journal Article
%T Archaeal Production of Polyhydroxyalkanoate (PHA) Co- and Terpolyesters from Biodiesel Industry-Derived By-Products
%A Carmen Hermann-Krauss
%A Martin Koller
%A Alexander Muhr
%A Hubert Fasl
%A Franz Stelzer
%A Gerhart Braunegg
%J Archaea
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/129268
%X 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 of 150£¿kDa and polydispersity of 2.1 for pure glycerol and 253£¿kDa and 2.7 for CGP, respectively; melting temperatures ranged between 130 and 140¡ãC in both setups. Supplying ¦Ã-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¡ãC) and glass transition temperature (2.5¡ãC), increased molar mass (391£¿kDa), and a polydispersity similar to the copolyesters. 1. Introduction Polyhydroxyalkanoates (PHAs) attract increasing attention as biobased, biocompatible, and biodegradable ¡°green plastics.¡± This is due to their promising material properties and sound integration of their life cycle into nature¡¯s closed carbon balance; neither their production nor their application or degradation causes negative ecological impacts [1]. These polyoxoesters of hydroxyalkanoic acids (HAs) constitute reserves for carbon and energy accumulated by various prokaryotic genera among eubacteria and archaea [2]. Factors generally supporting intracellular PHA biosynthesis are, similar to the accumulation of other microbial storage compounds such as glycogen, a high intracellular energy charge, characterized by high pools of acetyl-CoA, ATP, or NAD(P)H. Such conditions result from a sufficient supply of carbon substrates together with suboptimal availability of growth-determining components such as nitrogen, phosphate, or growth-essential micronutrients [1]. Depending on the provided carbon source and the microbial production strain, the material properties of PHA resemble those of
%U http://www.hindawi.com/journals/archaea/2013/129268/