Bacterial polyhydroxyalkanoates (PHAs) are attractive material as a bio-based alternative to petroleum-derived thermoplastics. We developed a microbial factory expressing engineered PHA synthetic enzymes that synthesizes a variety of novel biomaterials with superior properties. 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 unusual polymers, particularly LA-based polymers [1]. The chemically synthesized LA-based polyesters, such as poly(lactic acid) (PLA) are most widespread bio-based polymers because of their superior transparency and processability. Unlike the most of current chemical processes for PLA production including the LA fermentation and chemical polymerization of LA, our microbial processes produce LA-based polymers from renewable resources via one-pot fermentation. In addition, the enzymatic polymer synthesis under mild conditions allowed us to obtain extremely high enantio-pure polymers (nearly 100% ee) [2]. Further interesting feature is that the microbial factory synthesizes copolymers consisting of LA and bacterial PHA constituents, as a typical example, P(LA-co-3-hydroxybutyrate (3HB)). We have also synthesized copolymers containing the other monomers with varied side-chain-lengths of 3-hydroxyalkanoates (3HAs) using an evolved LPE [3]. In this talk, topics for the engineering approaches to synthesize new biopolymers will be introduced [4]. Especially, it should be noted that the unusual substrate specificity of LPE was found to be applicable to the synthesis of even other 2-hydroxyalkanoate (2HA) monomers; glycolate and 2-hydroxybutyrate [5]. This finding further expands the structural diversity in microbial polyesters. Xylose utilization was also an effective for production of LA-bases polymers [6].Acknowledgement The researches were financially supported by CREST project (5100270) of JST.References 1) S. Taguchi, et al., Proc. Natl. Acad. Sci. USA, 2008, 105(45), 17323-17327.2) M. Yamada, et al., Biomacromolecules, 2010, 10(4), 677-681.3) M. Yamada, et al., Biomacromolecules, 2010, 11(3), 815-819.4) K. Matsumoto and S. Taguchi, Curr. Opin. Biotechnol.,2013, 24(6), 1054-1060.5) K. Matsumoto et al., Biomacromolecules, 2013, 14(6), 1913-1918.6) J. M. Nduko et al., Metab. Eng., 2013, 15, 159-166.

Biosynthesis, properties, and enzymatic degradation of the 2-hydroxyalkanoate-based polyesters

248th National Meeting (2014)

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