Strong fibers and films of microbial polyesters

Poly [(R)-3-hydroxybutyrate] (P(3HB)) and its copolymers are accumulated by a wide variety of micro-organisms as intracellular carbon and energy material, and are extensively studied as biodegradable and biocompatible thermoplastics. However, these microbial polyesters have not been recognized as practical because of their stiffness and brittleness. Recently, by new drawing techniques, we succeeded in obtaining strong fibers and films from microbial polyesters, produced by both wild-type and recombinant bacteria. The improvement in mechanical properties of the fibers and films is due not only to the orientation of molecular chains, but also to the generation of a zigzag conformation and network structure, formed by fibrillar and lamellar crystals. The structure of strong fibers with a tensile strength over 1.0 GPa was analyzed by micro-beam X-ray diffraction with synchrotron radiation. The strong fibers and films were completely degraded in natural, river freshwater or by extracellular polyhydroxybutyrate depolymerases. In this feature article. the processing, mechanical properties, highly ordered structure and biodegradability of strong fibers and films produced from microbial polyesters are presented.