bioplasticsMAGAZINE_1201

Foam
A
B
CO 2
CO 2
Photosynthesis/
carbon fixation
Photosynthesis/
carbon fixation
Figure 2:
(a) Synthesis of PHBV by
bacterial fermentation process;
(b) Direct synthesis of PHBV in
crop plants. Graphic according to
Y. Poirier, Nature Biotechnology,
Vol. 17, p. 960, 1999
Propionic
acid
Starch
Glucose
PHBV
Harvest &
processing
Fermentation
Harvest &
processing
Threonine 2-ketobutyrate isoleucine
Propionyl-CoA
Acetyl-CoA Fatty acids
PHBV
PHBV
Harvest &
processing
PHBV foams and its
By
Alireza Javadi 1,2 , Srikanth Pilla 2 ,
Lih-Sheng Turng 2,3 , Shaoqin Gong 1,2
1
Department of Biomedical Engineering,
University of Wisconsin–Madison, WI, USA
2
Wisconsin Institute for Discovery,
Madison, WI, USA
3
Department of Mechanical Engineering,
University of Wisconsin–Madison, WI, USA
3HB
PHBV
3HV
Figure 2: Schematic chemical structure of Poly
(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).
Introduction
In the past few years, extensive research on biobased and
biodegradable polymers has led to a better understanding
of their properties and morphologies, as well as their
structure–property relationship. Poly(hydroxyalkanoates)
(PHAs), a family of linear polyesters produced in nature by
bacterial fermentation of various renewable sources such
as sugars, lipids, and alkanoic acids, are among the most
promising biobased and biodegradable materials currently
being investigated [1]. Among PHAs, poly(3-hydroxybutyrate)
(PHB) and its copolymers Poly(3-hydroxybutyrate-co-3-
hydroxyvalerate) (PHBV) have attracted a lot of attention in
the past two decades due to their unique properties. PHBV
is either produced directly from plants or synthesized by
microorganisms by consuming sugars in the presence of
propionic acid (Figure 1) [2]. PHBV (Figure 2) is available
commercially under various names including Tianan
Biologic’s ENMAT Y1000P, Biomer’s Biomer L, and
Metabolix’s Mirel.
In spite of improved mechanical (e.g., toughness) and
thermal properties compared to PHB, PHBV still exhibits
some disadvantages including low strain-at-break, narrow
processing window, slow crystallization rate, and higher cost
as compared to petroleum-based synthetic polymers [3].
In order to tailor its properties and decrease its total cost,
several approaches have been proposed such as forming
blends or composites with biodegradable polymers, natural
fillers, or inorganic fillers.
PHBV-based polymer blends and composites have
been extensively studied in order to reduce their material
cost, improve their processability, and engineer their
28 bioplastics MAGAZINE [01/12] Vol. 7