High-functionability of ultra-high-molecular-weight biodegradable polyesters produced by recombinant Escherichia coli

点击翻译按钮获取中文摘要

Poly([R]-3-hydroxybutyrate) (P(3HB)) is accumulated by a wide variety of microorganisms as intracellular carbon and energy material, and is extensively stud led as a biodegradable and biocompatible thermoplastic. However, the mechanical properties of P(3HB) homopolymer films markedly deteriorate by secondary crystallization. Recently, we succeeded in obtaining strong P(3HB) films and fibers by cold-drawing and two-step drawing procedures. The tensile strength of P(3HB) fiber is over 1.3 GPa. The improvement of mechanical properties is due not only to the orientation of molecular chains but also to the generation of a zigzag conformation and network structure formed by fibril and lamellar crystals. The mechanical properties remained unchanged for 6 months. These strong films and fibers were completely degraded in natural river freshwater within 4 weeks. The rate of erosion of P(3HB) films was controlled by the crystallinity of materials. P(3HB) single crystals were prepared from a dilute solution by isothermal crystallization. Enzymatic degradation of single crystals progressed from the edge of the crystals, or along their long axis while making small fragments.