Polyhydroxyalkanoates:

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Polyhydroxyalkanoates Microbial Biopolymers
Peter Jantz Chemistry 496 May 7th, 2004
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Overview

• Traditional Polymers
• What are Biopolymers?
• How Biopolymers are Synthesized
• Environmental Benefits
• The Future of Biopolymers

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Traditional Polymers Structure
Polystyrene Coffee cups, Fast-food
Polyethylene HDPE Milk containers LDPE
Plastic bags, Packaging Polyvinyl chloride
Piping, Meat wrap Polyethylene terephthalate
Soda bottles
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Expenses of Traditional Polymers

• Production of 1 pound of polystyrene requires
  2.26 pounds of oil.
• 1 lb provides the carbon monomers and the
  remaining 1.26 lbs of oil are burned to produce
  the electrical power to run the reaction.
• Organic solvent 1,2-dichloroethane (30 per
  liter)
• Reaction Initiator boron trifluoride with water
  (20 per gram)

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Environmental effects

• Oil use 100 billion pounds of plastics are
  produced in North America annually
• Only 3 of these plastics are recycled
• Barely 25 of all soda bottles are recycled

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What are Biopolymers?

• Energy storage for bacteria
• Physical properties of polyethylene, polystyrene,
  and synthetic polyesters
• Polyhydroxyalkanoates

Polyhydroxybutyrate
Polyhydroxyvalerate
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Synthetic Conditions

• Anaerobic Environment
• Abundant carbon source
• 3-hydroxyacyl-CoA polymerization

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PHA Synthesis from fatty acids
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PHA Synthesis from a carbon source
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3-hydroxyacyl CoA polymerization
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Processing

• A carbon source (corn) is ground into a mash and
  fed to PHA-forming bacteria
• Glucose is extracted as the microbes ferment the
  mash and store the energy as PHAs
• The cells are washed and lysed
• The PHAs are separated by centrifuge and washed
  again

30 PHA by dry weight
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Biodegradability
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Monetary Costs

• 3x higher than petroleum-based plastics
• High start-up costs
• Labor intensive processing
• High energy demands

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Environmental effects

• Good
• Ocean pollution would decrease
• Landfill space would decrease (anaerob.)
• Recycling costs could be saved

• Bad
• Air pollution would increase significantly
• 2.39 pounds of fossil fuel are burned for each
  pound of PHA produced

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Is there a future for Biopolymers?

• With greater financial and environmental costs,
  how will renewable biodegradable polymers take a
  hold in industry and with consumers?

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Mustard!!
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Genetic transfer to plants

• Mustard and alfalfa
• Restriction Endonuclease gene insertion
• Use carbon-dioxide as carbon source
• 14 PHA by dry weight
• Cheaper processing

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References
1 T. Gerngross. Plastic from plants called
costly New Orleans ACS meeting. August 25,
1999 2 C. Nawrath et al. Targeting of the
polyhydroxybutyrate biosynthetic pathway to the
plastids of Arabidopsis thaliana results in high
levels of polymer accumulation. Proc. Natl.
Acad. Sci. U.S.A., 12760, 1994. 3 Yong Jia
et al. Mechanistic Studies on Class I
Polyhydroxybutyrate (PHB) Synthase from Ralstonia
eutropha Class I and III Synthases Share a
Similar Catalytic Mechanism. Biochemistry, 1011
-1019, 2001. 4 Shiming Zhang et al. Mechanism
of the Polymerization Reaction Initiated and
Catalyzed by the Polyhydroxybutyrate Synthase of
Ralstonia eutropha. Biomacromolecules, 504 -509,
2003. 5 Si Jae Park et al. Production of
Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by
Metabolically Engineered Escherichia coli
Strains. Biomacromolecules, 248 -254, 2001. 6
Lin Su et al. Enzymatic Polymerization of (R )-3-
Hydroxyalkanoates by Bacterial Polymerase.
Macromolecules, 229 -231, 2000.
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the End.