Introduction
The accumulation of petrochemical plastic waste in the
environment is an increasing problem. In order to find
alternative materials, researchers have developed fully
biodegradable plastics, such as polyhydroxyalkanoates
(PHAs). PHAs extracted from bacterial cells show material
properties that are similar to polypropylene (Braunegg
et al. 1998). Many micro-organisms have the ability to
degrade these macromolecules enzymatically (Mergaert
et al. 1992). Other advantages of these materials over petrochemical
plastics are that they are natural, renewable
and biocompatible.
The occurrence of PHAs in bacteria has been known
since 1920s, when Lemoigne reported the formation of
poly(3-hydroxybutyrate) (PHB) inside bacteria (Lemoigne
1926).
However, the high cost of producing these bioplastics
and the availability of low-cost petrochemical-derived
plastics led to bioplastics being ignored for a long time.
Concern over petrochemical plastics in the environment
has created a renewed interest in biologically derived polymers.
During recent years, intensive research has investigated