Polyesters

Question 1

Polyhydroxyalkanoate (PHA) is produced by ______________.

Answer 1

direct fermentation

Question 2

What are the three groups of PHAs?

Answer 2

1. short-chain-length (SCL) - 3-5 C
2. medium-chain-length (MCL) - 6-14 C
3. long-chain-length (LCL) - 17-18 C

Question 3

Where do substrates come from for PHA synthesis?

Answer 3

1. cheese and sour milk production wastes
2. materials from sugar industry
3. wastes from palm oil production
4. wastes from cooking oil and fats
5. residues of animal fats - into triglycerides
6. meat and bone waste hydrolysates

Question 4

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

Answer 4

1. chemical composition of the polymers produced under different cultivation and PHA-producing bacterial strains
2. carbon nutrition conditions

Question 5

List the 8 general properties of PHA

Answer 5

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

Question 6

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

Answer 6

1. crystallinity
2. mechanical strength
3. temperature characteristics
4. degradation rates

Question 7

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

Answer 7

1. degree of crystallinity
2. melting point
3. ductility
4. mechanical strength
5. degradation rate

Question 8

What are short-chain-length PHAs used for?

Answer 8

1. fabricate packaging films, shopping bags, containers, and paper coatings
2. everyday use items e.g. toys, sports equipment, disposable dishes, hygiene products, etc.

Question 9

List the 5 applications of PHAs

Answer 9

1. glues and fillers
2. garbage bags
3. personal hygiene materials
4. dairy cream substitutes
5. flavor delivery agents

Question 10

List the 8 medical applications of PHAs

Answer 10

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

Question 11

Polyhydroxy butyrate (PHB) are made from _______________

Answer 11

renewable biomass

Question 12

What are the three groups of PHBs?

Answer 12

1. low MW - aka complexed PHB (cPHB)
2. high MW - depends on growth conditions
3. ultra high MW

Question 13

What is ultra high MW PHB used for?

Answer 13

blending or composite material

Question 14

What are the two carbon chain classifications for PHB?

Answer 14

1. short-chain-lengths (SCL) - 3-5 C
2. medium-chain-lengths (MCL) - 6-14 C

Question 15

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

Answer 15

low crystalline elastomeric thermoplastics

Question 16

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

Answer 16

sugars and plant oils

Question 17

________ and _______ promotes PHB accumulation

Answer 17

feeding medium and carbon

Question 18

Production of PHB is directly proportional to the __________ ratio

Answer 18

Carbon to nitrogen

Question 19

What is the non-medical applications of PHB

Answer 19

packaging - blow molded bottles

Question 20

What are the medical applications of PHB?

Answer 20

1. pericardial patches
2. vascular grafts
3. heart valves
4. controlled drug release
5. tissue scaffolds

Question 21

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

Answer 21

high production costs

Question 22

What is the main contributor to the overall PHB production cost

Answer 22

carbon substrate cost

Question 23

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

Answer 23

1. efficient bacterial strains
2. optimizing fermentation and recovery processes