The production of bio-based polymers has become increasingly important owing to accelerated fossil fuel depletion and environmental pollution. Bio-based polymers can be classified into three main groups. Bio-based polymers in the first group, e.g., polyhydroxyalkanoates (PHAs), are entirely synthesized by biological processes. Microbial host strains synthesize polymers using monomers produced by their inherent and recombinant metabolic pathways from renewable resources. Most currently available biopolymers belong to the second group, in which all or some monomers and/or monomer precursors for polymers produced by microbial fermentations are purified to polymer-grade products and employed for chemical polymer synthesis. Polybutylene succinate (PBS), polytrimethylene terephthalate (PTT), polylactic acid (PLA), and some bio-nylons belong to this group. Polymers in the third group are synthesized entirely by chemical processes. Specifically, polymers are chemically synthesized using monomers that are chemically produced from biomasses. In this chapter, we focus on the first and second groups and discuss current advances in the development of metabolically engineered microorganisms for the production of bio-based plastics. In particular, we clarify the technological feasibility of metabolic engineering strategies for the in vivo synthesis of PLA, PLGA, and their copolymers and for the production of bio-nylon monomers.
This work was supported by the Technology Development Program to Solve Climate Changes on Systems Metabolic Engineering for Biorefineries from the Ministry of Science and ICT (MSIT) through the National Research Foundation (NRF) of Korea (NRF-2015M1A2A2035810) and Mid-career Researcher Program through NRF grant funded by the MSIT (NRF-2016R1A2B4008707).
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