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.
Biotechnol Adv. 2012 Nov-Dec;30(6):1196-206. doi: 10.1016/j.biotechadv.2011.11.007. Epub 2011 Nov 25.
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.
聚羟基脂肪酸酯（PHA）是一种生物聚酯，通常由 3-、4-、5-和 6-羟基羧酸组成，这些酸在有限的生长条件下作为碳和能量储存物质积累，当存在过量碳源时。由于 PHA 合成酶（PHA 生物合成的关键酶）具有不同的底物特异性，通过将不同组成的不同单体成分掺入其中，可以合成具有不同材料性能的 PHAs。此外，通过体外定向进化和定点突变工程 PHA 合成酶，可以拓宽用于 PHA 生物合成的单体范围，从而合成具有新型材料性能的 PHA 共聚物。基于对 PHA 生物合成代谢的理解，通过表达异源 PHA 生物合成基因以及创建和增强代谢途径来有效生成 PHA 单体的前体，已经对重组细菌进行了工程改造以生产不同类型的 PHAs。最近，通过使用天然和工程化的 PHA 合成酶，PHA 生物合成系统已扩展到生产含有 2-羟基酸单体（如乙醇酸、乳酸和 2-羟基丁酸）的非天然生物聚酯。使用该系统，可以通过重组细菌的直接发酵，从可再生资源中合成聚乳酸（PLA）等主要商业可用的生物塑料。在本文中，我们讨论了 PHA 生物合成系统作为具有新型材料性能的定制聚酯平台的最新进展。
