Biosynthesis of 2-hydroxyacid containing polyhydroxyalkanoates in metabolically engineered Ralstonia eutropha

Si Jae Parka, Seung Hwan Leeb, Young Hoon Ohb, Jung Eun Yangc, So Young Choic, Sang Yup Leec

aDepartment of Environmental Engineering and Energy, Myongji University, Republic of Korea

bKorea Research Institute of Chemical Technology, Republic of Korea

cMetabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, Republic of Korea

*Correspondence should be addressed to Sang Yup Lee (leesy@kaist.ac.kr) and Seung
Hwan Lee (hwanlee@krict.re.kr).
Polyhydroxyalkanoates (PHAs) are microbially derived bio-based polyesters synthesized by many microorganisms. Since material properties of PHAs are highly dependent upon their types and compositions of monomers, researches have been focused on the development of microbial system to design polyesters containing novel monomers, which might confer superior material properties.
We have metabolically engineered E. coli strains for the production of 2-hydroxyacids containing PHAs such as lactate-containing PHAs, polylactic acid (PLA), and 2- hydroxybutyrate (2HB)-containing PHAs from structurally unrelated carbon sources by one-step fermentative process. PHAs consisting of 2-hydroxyacids as monomer units have attracted much attention, but their production has not been efficient.
Since Ralstonia eutropha is the most efficient host strain for the production of PHAs from renewable resources, here, we report the metabolic engineering strategies for the development of recombinant Ralstonia eutropha strains to synthesize PHAs containing
2-hydroxyacids as monomers. This could be achieved by the construction of base R. eutropha strains that express engineered PHA synthase able to use 2-hydroxyacyl-CoAs (2HA-CoAs) as substrates and engineered propionyl-CoA transferase to synthesize
2HA-CoAs. Detailed metabolic engineering strategies for the construction of versatile recombinant R. eutropha strains to produce PHAs containing various 2-hydroxyacid monomers will be presented.

[This work was supported by the Technology Development Program to Solve Climate Changes

(Systems Metabolic Engineering for Biorefineries) from the Ministry of Science, ICT and

Future Planning (MSIP) through the National Research Foundation (NRF) of Korea (NRF-

2012-C1AAA001-2012M1A2A2026556)].