Chemistry Reference
In-Depth Information
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CHAPTER 5
Nanocomposites of
Polyhydroxyalkanoates (PHAs)
A. M. GUMEL AND M. S. M. ANNUAR*
Institute of Biological Sciences, Faculty of Science, University of Malaya,
50603 Kuala Lumpur, Malaysia
*Email: suan_annuar@um.edu.my
5.1 Introduction
Polyhydroxyalkanoates (PHAs) are a group of polyhydroxyesters with diverse
structures. The composition of these polyesters may include 3-, 4-, 5- and
6-hydroxyalkanoic acid monomers that are accumulated by different bac-
terial species (native or mutant) under nutrient(s)-deprived conditions but
abundant carbon sources. A wide range of carbon sources could serve as
substrate(s) for microbial PHA accumulation but in terms of its mass pro-
duction, the use of renewable resources such as fatty acids is very favor-
able.
1-3
The accumulated PHAs serve as a carbon and energy reserve within
the microorganisms.
4
A range of PHAs comprising both copolymers and
block copolymers has been produced using different processes including
fermentation and enzymatic catalysis, leading to an accumulated PHA con-
tent of as much as 90% of the microbial dry mass.
5
Moreover, alternative
production schemes based on genetically modified plants and yeast are
currently gaining momentum and may become the preferred route for PHA
production.
5
Unlike petrochemical-derived plastics, PHAs are biodegrad-
able, and are biocompatible with gas-barrier properties almost similar to
those of polyvinyl chloride and polyethylene terephthalate.
6
These combin-
ations of excellent physico-chemical properties warrant the increasing
.
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