1. Introduction
Polyhydroxyalkanoates are biodegradable polymers, with thermoplastic,
elastomeric and adhesive properties comparable to
synthetic polyesters, upon composition of the monomer unit, the
microorganism used in fermentation, as well as the nature of the
carbon source [1,2]. They are widely distributed in nature and
accumulate in various bacteria as intracellular carbon and energy
storage materials in the form of water-insoluble granules [3]. Since
they can be produced from renewable carbon resources, PHAs can
play a positive role in agriculture, the environment and the economy,
contributing to the conservation of finite fossil resources, such
asmineral oil and coal, and are neutral with regard to CO2 emissions
[4].
Based on their repeat unit compositions, PHAs belong to two
main groups and blends: short-chain-length (scl-) PHAs with
hydroxy fatty acid (HFA) repeat units, 3–5 carbon chain length
(C3–C5), and medium-chain-length (mcl-) PHAs with C6 and longer
repeat units. In general, scl-PHAs are thermoplastics with various
degrees of crystallinity and are brittle and stiff [5]; whereas
mcl-PHAs with low crystallinity, low glass transition temperatures,
low tensile strength and high elongation to break ratios, are