Tailor-made type II Pseudomonas PHA synthases and their use for the biosynthesis of polylactic acid and its copolymer in recombinant Escherichia coli

Taek Ho Yang, Yu Kyung Jung, Hye Ok Kang, Tae Wan Kim, Si Jae Park, Sang Yup Lee

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58 Scopus citations

Abstract

Previously, we have developed metabolically engineered Escherichia coli strains capable of producing polylactic acid (PLA) and poly(3-hydroxybutyrate- co-lactate) [P(3HB-co-LA)] by employing evolved Clostridium propionicum propionate CoA transferase (Pct Cp ) and Pseudomonas sp. MBEL 6-19 polyhydroxyalkanoate (PHA) synthase 1 (PhaC1 Ps6-19). Introduction of mutations four sites (E130, S325, S477, and Q481) of PhaC1 Ps6-19 have been found to affect the polymer content, lactate mole fraction, and molecular weight of P(3HB-co-LA). In this study, we have further engineered type II Pseudomonas PHA synthases 1 (PhaC1s) from Pseudomonas chlororaphis, Pseudomonas sp. 61-3, Pseudomonas putida KT2440, Pseudomonas resinovorans, and Pseudomonas aeruginosa PAO1 to accept short-chain-length hydroxyacyl-CoAs including lactyl-CoA and 3-hydroxybutyryl-CoA as substrates by site-directed mutagenesis of four sites (E130, S325, S477, and Q481). All PhaC1s having mutations in these four sites were able to accept lactyl-CoA as a substrate and supported the synthesis of P(3HB-co-LA) in recombinant E. coli, whereas the wild-type PhaC1s could not accumulate polymers in detectable levels. The contents, lactate mole fractions, and the molecular weights of P(3HB-co-LA) synthesized by recombinant E. coli varied depending upon the source of the PHA synthase and the mutants used. PLA homopolymer could also be produced at ca. 7 wt.% by employing the several PhaC1 variants containing E130D/S325T/S477G/Q481K quadruple mutations in wild-type E. coli XL1-Blue.

Original languageEnglish
Pages (from-to)603-614
Number of pages12
JournalApplied Microbiology and Biotechnology
Volume90
Issue number2
DOIs
StatePublished - Apr 2011

Bibliographical note

Funding Information:
Acknowledgements We thank Sun Ok Oh (LG Chem) for her help with the GPC analysis. This work was supported by LG Chem and by the Korean Systems Biology Research Project (20090065571) of the Ministry of Education, Science and Technology (MEST). Further supports by the World Class University Program (R32-2008-000-10142-0) through the National Research Foundation of Korea funded by the MEST and LG Chem Chair Professorship are appreciated.

Keywords

  • P(3HB-co-LA)
  • PLA
  • Pseudomonas PhaC1 variants
  • Site-directed mutagenesis

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