Sustainable Bioplastics

Biography

Biography: Seiichi TAGUCHI

Abstract

Biologically synthesized polyhydroxyalkanoates (PHAs) are attractive materials as bio-based alternatives to petroleum-derived thermoplastics. We developed a microbial platform carrying evolutionarily engineered PHA synthetic enzymes that confer high enantio-selectivity and broad substrate specificity toward monomeric constituents. The finding of an engineered PHA synthase with lactate (LA)-polymerizing activity (Lactate Polymerizing Enzyme, LPE) was a major breakthrough to achieve the microbial production of the diverse polymers, particularly LA-based polymers. Poly(lactic acid) (PLA) is most widespread bio-based polymer due to its superior transparency and processability. Our microbial processes produce LA-based polymers from renewable resources via one-pot fermentation. In this talk, topics for the engineering approaches to synthesize new biopolymers will be introduced together with the polymer biodegradation. Especially, combination of metabolic engineering and enzyme engineering are very powerful toolboxes for this purpose. Recently, using analytical GC-MS, we established the quantitative metabolite analysis procedure to address the rate-limiting step for synthesis of LA-based polymers. This new analytical system actually provided us with improved production of PLA-related polymers. This strategy should be applicable to a wide range of PHA-producing systems. It should also be noted that the unusual substrate specificity of LPE was found to be applicable to the synthesis of PLA-related polymers incorporating even other 2-hydroxyalkanoate (2HA) monomers; glycolate and 2-hydroxybutyrate. This finding further expands the structural diversity in microbial polyesters. Xylose utilization was also an effective for production of PLA-related polymers with respect to realizing the value chain system from raw biomass to value-added biomaterials.