Microbial synthesis and enzymatic degradation of renewable poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate]

Abstract

This paper reports our recent progress on a microbial system for efficient production of biodegradable copolyester of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate], P(3HB-co-3HHx), with desirable copolymer compositions using genetically engineered bacteria. We have developed a fermentation technique to achieve high cell density cultivation of a recombinant Ralstonia eutropha using inexpensive soybean oil as a sole carbon source. In addition, we demonstrate that the use of polyhydroxyalkanoate (PHA) synthase (PhaC) mutants having an amino acid substitutions is able to vary the copolymer composition of P(3HB-co-3HHx) synthesized from soybean oil by the recombinant bacteria. On the other hand, it is also important to understand the enzymatic degradation process of PHA materials for establishing a method to regulate the rate of biodegradation. The enzymatic degradation process of P(3HB-co-3HHx) thin film using an extracellular PHB depolymerase has been studied by in situ atomic force microscopy in buffer solution. We demonstrate that the PHA depolymerase predominantly degrades the less-ordered molecular chain-packing regions along the crystallographic a-axis. q

Solubility and degradation of polyhydroxyalkanoate biopolymers in propylene carbonate

“…These polymers have a wide range of performance characteristics and can be produced in various wild‐type and recombinant microorganisms. Also, many PHAs can be made from various natural substrates and waste streams3–5 and many are biodegradable 6–9…”

Controlled biosynthesis and characterization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) from mixtures of palm kernel oil and 3HV-precursors

“…The copolymers consisting of short-chain-length (SCL) and medium-chain-length (MCL) 3-hydroxyalkanoates possess better properties compared to SCL or MCL polymers [2]. The combination of SCL and MCL monomer units in P(3HB-co3HHx) exhibits suitable material properties with higher flexibility ideal for commercial uses [3]. Kahar and co-workers have successfully attained high yield production of this copolymer from soybean oil [4].…”

Production and characterization of terpolyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) by recombinant Aeromonas hydrophila 4AK4 harboring genes phaAB

“…These bacterial PHA have attracted much attention for application as biodegradable and biocompatible thermoplastics [5][6][7]. Bacterial PHA can be divided into three types depending on the number of carbon atoms in the monomeric units: short-chain-length (SCL) containing less than six carbon atoms in their monomers, medium-chain-length (MCL) possessing six and more carbon atoms as monomers, and SCL-MCL copolymers PHA [8].…”