Abstract
Polyhydroxyalkanoates (PHAs) containing hydroxyl groups in a side chain were produced in recombinant Escherichia coli JM109 using glycolate as the sole carbon source. The propionate-CoA transferase (pct) gene from Megasphaera elsdenii and the β-ketothiolase (bktB) gene and phaCAB operon from Ralstonia eutropha H16 were introduced into E. coli JM109. A novel monomer containing a hydroxyl group, dihydroxybutyrate (DHBA), was the expected product of the condensation of glycolyl-CoA and acetyl-CoA by BktB. The recombinant strain produced a PHA containing 1 mol% DHBA. The incorporation of DHBA may have been restricted because the expression of phaAB1 competes for acetyl-CoA. The PHA containing DHBA units were evaluated regarding thermal properties, such as melting temperature, glass transition temperature and thermal degradation temperature. The current study demonstrates a potential use of PHA containing hydroxyl groups as renewable resources in biological materials.
Highlights
Polyhydroxyalkanoates (PHAs), which are one of biodegradable polyesters, are produced intracellularly by a wide variety of microorganisms from carbon and energy storage compounds under unbalanced growth conditions (Doi et al 1995; Madison and Huisman 1999; Rehm 2007)
In this study, we demonstrated the biosynthesis of PHA containing side chains with hydroxyl groups in E. coli JM109 by introducing pct from M. elsdenii and the bktB and phaCAB operons from R. eutropha H16
Construction of the recombinant strain The PHA biosynthesis pathway in E. coli JM109 was constructed by introducing the plasmid containing the phaCAB operon from R. eutropha H16
Summary
Polyhydroxyalkanoates (PHAs), which are one of biodegradable polyesters, are produced intracellularly by a wide variety of microorganisms from carbon and energy storage compounds under unbalanced growth conditions (Doi et al 1995; Madison and Huisman 1999; Rehm 2007). Their results have indicated the possibility of incorporating a DHBA unit into PHA by using the pct, bktB and phaB genes. In this study, we demonstrated the biosynthesis of PHA containing side chains with hydroxyl groups in E. coli JM109 by introducing pct from M. elsdenii and the bktB and phaCAB operons from R. eutropha H16.
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