Polyhydroxyalkanoates (PHAs), their Blends, Composites and Nanocomposites: State of the Art, New Challenges and Opportunities - Polyhydroxyalkanoate (PHA) Based Blends, Composites and Nanocomposites - page 1

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CHAPTER 1
Polyhydroxyalkanoates (PHAs),
their Blends, Composites and
Nanocomposites: State of the
Art, New Challenges and
Opportunities

VISAKH P. M.

Senior Researcher, School of Chemical Sciences, Mahatma Gandhi
University, Kottayam, Kerala, India
Email: [e-mail]

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1.1 Polyhydroxyalkanoates: Structure, Properties and
Sources
Polyhydroxyalkanoates are biopolyesters with various side chains and
fatty acids with hydroxyl groups at the 4- or 5-position. They consist of (R)-3-
hydroxy fatty acids. There are three types of polyhydroxyalkanoates: (a) short
chain length hydroxyalkanoic acids (PHA SCL ) with an alkyl side chain, which
are produced by Ralstonia eutropha and many other bacteria. PHA SCL contain
3-5 carbon atoms, for example poly-3-hydroxybutyrate (P3HB), poly-4-
hydroxybutyrate (P4HB); (b) medium chain length hydroxyalkanoic
acids (PHA MCL ) with alkyl side chains that are produced by Pseudomonas
oleovorans and other Pseudomonas sensu stricto.PHA MCL contain 6-14 carbon
atoms and (c) long chain length (PHA LCL ) obtained from long chain fatty