BME 312 Exam 3: Polyester

 Polyhydroxyalkanoate (PHA) is produced by ______________. 

direct fermentation

What are the three groups of PHAs?

• Short-chain-length (SCL) - 3-5 C

• Medium-chain-length (MCL) - 6-14 C

• Long-chain-length (LCL) - 17-18 C

Where do substrates come from for PHA synthesis?

• Cheese and sour milk production wastes

• Materials from sugar industry

• Wastes from palm oil production

• Wastes from cooking oil and fats

• Residues of animal fats - into triglycerides

• Meat and bone waste hydrolysates

The degree of crystallinity of PHAs is controlled and depends on ___________

• Chemical composition of the polymers produced under different cultivation and PHA-producing bacterial strains

• Carbon nutrition conditions

List the 8 general properties of PHA

1. Biodegradable - in biological media

2. Biocompatible

3. Low permeability to water

4. UV resistant

5. Optical activity

6. Antioxidant

7. Piezoelectricity charge

8. High tensile strength

What properties of PHAs can be controlled by varying the composition of the culture medium and tailoring the chemical structure of the polymer?

• Crystallinity

• Mechanical strength

• Temperature characteristics

• Degradation rates

There are various PHA copolymers that differ in the following properties __________ (5)

• Degree of crystallinity

• Melting point

• Ductility

• Mechanical strength

• Degradation rate

What are short-chain-length PHAs used for?

• Fabricate packaging films, shopping bags, containers, and paper coatings

• Everyday use items e.g. toys, sports equipment, disposable dishes, hygiene products, etc.

List the 5 applications of PHAs

1. Glues and fillers

2. Garbage bags

3. Personal hygiene materials

4. Dairy cream substitutes

5. Flavor delivery agents

 List the 8 medical applications of PHAs

1. Cardiac patch and heart valve

2. Stent

3. Drug delivery

4. Wound dressing

5. Nerve guidance conduit

6. Blood vessel

7. Sutures

8. Bone and cartilage scaffold

Polyhydroxy butyrate (PHB) are made from _______________

Renewable biomass

What are the three groups of PHBs?

• Low MW - aka complexed PHB (cPHB)

• High MW - depends on growth conditions

• Ultra high MW

What is ultra high MW PHB used for?

Blending or composite material

What are the two carbon chain classifications for PHB?

• Short-chain-lengths (SCL) - 3-5 C

• Medium-chain-lengths (MCL) - 6-14 C

The conversion from SCL to MCL results in change from crystalline to ____ _________ ___________ thermoplastics

Low crystalline elastomeric thermoplastics

Production of PHB is directly proportional to the __________ ratio

Carbon to nitrogen

________ and _______ promotes PHB accumulation

Feeding medium and carbon

What is the non-medical applications of PHB

Packaging - blow molded bottles

PHB can be produced by ________ and ________ (wastes).

Sugars and plant oils

What two methods have been used to reduce the cost of PHB

1. Efficient bacterial strains

2. Optimizing fermentation and recovery processes

A major problem for production of PHBs is their ____ _________________ _______

High production costs

What is the main contributor to the overall PHB production cost

Carbon substrate cost

What are the medical applications of PHB?

• Pericardial patches

• Vascular grafts

• Heart valves

• Controlled drug release

• Tissue scaffolds