•Traditional Polymers
•What are Biopolymers?
•How Biopolymers are Synthesized
•Environmental Benefits
•The Future of Biopolymers
Polystyrene: Coffee cups, Fast-food
Polyethylene:
HDPE: Milk containers
LDPE: Plastic bags, Packaging
Polyvinyl chloride: Piping, Meat wrap
Polyethylene terephthalate: Soda bottles
•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)
• 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
• Energy storage for bacteria
• Physical properties of polyethylene, polystyrene, and synthetic polyesters
• Polyhydroxyalkanoates
HC CH2O C
CH3 O
Polyhydroxybutyrate Polyhydroxyvalerate
HC CH2O C
CH2 O
CH3
• Anaerobic Anaerobic EnvironmentEnvironment
• Abundant carbon Abundant carbon sourcesource
• 3-hydroxyacyl-CoA 3-hydroxyacyl-CoA polymerizationpolymerization
HC CH2O C
CH3 O
HC CH2O C
CH2 O
CH3
• A carbon source (corn) is ground into a mash A carbon source (corn) is ground into a mash and ‘fed’ to PHA-forming bacteriaand ‘fed’ to PHA-forming bacteria
• Glucose is extracted as the microbes ferment Glucose is extracted as the microbes ferment the mash and store the energy as PHA’sthe mash and store the energy as PHA’s
• The cells are washed and lysedThe cells are washed and lysed
•The PHA’s are separated by centrifuge and The PHA’s are separated by centrifuge and washed againwashed again
30% PHA by dry weight30% PHA by dry weight
3x higher than petroleum-based plastics
– High start-up costs
– Labor intensive processing
– High energy demands
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
=o)
=o(
With greater financial and environmental costs, how will renewable biodegradable polymers take a hold in industry and with consumers?
• Mustard and alfalfa– Restriction Endonuclease gene
insertion– Use carbon-dioxide as carbon
source– 14% PHA by dry weight– Cheaper processing
[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.