title: Advanced bacterial polyhydroxyalkanoates: towards a versatile and sustainable platform for unnatural tailor-made polyesters.
abstract: Polyhydroxyalkanoates (PHAs) are biopolyesters that generally consist of 3-, 4-, 5-, and 6-hydroxycarboxylic acids, which are accumulated as carbon and energy storage materials in many bacteria in limited growth conditions with excess carbon sources. Due to the diverse substrate specificities of PHA synthases, the key enzymes for PHA biosynthesis, PHAs with different material properties have been synthesized by incorporating different monomer components with differing compositions. Also, engineering PHA synthases using in vitro-directed evolution and site-directed mutagenesis facilitates the synthesis of PHA copolymers with novel material properties by broadening the spectrum of monomers available for PHA biosynthesis. Based on the understanding of metabolism of PHA biosynthesis, recombinant bacteria have been engineered to produce different types of PHAs by expressing heterologous PHA biosynthesis genes, and by creating and enhancing the metabolic pathways to efficiently generate precursors for PHA monomers. Recently, the PHA biosynthesis system has been expanded to produce unnatural biopolyesters containing 2-hydroxyacid monomers such as glycolate, lactate, and 2-hydroxybutyrate by employing natural and engineered PHA synthases. Using this system, polylactic acid (PLA), one of the major commercially-available bioplastics, can be synthesized from renewable resources by direct fermentation of recombinant bacteria. In this review, we discuss recent advances in the development of the PHA biosynthesis system as a platform for tailor-made polyesters with novel material properties.
authors.affiliation: Chemical Biotechnology Research Center, Green Chemistry Division, Korea Research Institute of Chemical Technology, P.O.Box 107, Sinseongno 19, Yuseong-gu, Daejeon 305-600, Republic of Korea. parksj@krict.re.kr
authors.forename: Si Jae
authors.initials: SJ
authors.lastname: Park
authors.forename: Tae Wan
authors.initials: TW
authors.lastname: Kim
authors.forename: Min Kyung
authors.initials: MK
authors.lastname: Kim
authors.forename: Sang Yup
authors.initials: SY
authors.lastname: Lee
authors.forename: Sung-Chul
authors.initials: SC
authors.lastname: Lim
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism*; D005285:Fermentation; D019344:Lactic Acid / Q000378:metabolism; D060847:Metabolic Engineering; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis*
chemical_list: D054813:Polyhydroxyalkanoates; D019344:Lactic Acid; D000217:Acyltransferases; C077225:poly(3-hydroxyalkanoic acid) synthase