Name the biopolymer.
Polyhydroxyalkanoates (PHAs) is a biodegradable plastic.
Draw a structural diagram of the biopolymer
The three types of polyhydroxyalkanoates: poly 3- hydroxobutyrate (PHB), poly 3-hydroxobutyrate-co-3-hydroxyvalerate (PHBV), ), poly 3-hydroxobutyrate-co-4-hydroxyvalerate (PH3B).
Name the specific enzyme used or organism to synthesis the material.
Polyhydroxyalkanoate is synthesised by bacteria.
Describe the process used to synthesise the material.
They are produced by bacterial fermentation. To produce PHA a culture of microorganisms, such as Alcalingenes eutrophus, is placed in a suitable medium and fed appropriate nutrients so that it multiplies rapidly and the number of the microorganisms increases. The main nutrient required by the bacteria is glucose, glucose is a renewable resource so it is readily available. The 'diet' of the organism is changed to restrict the supply of one particular nutrient, such as nitrogen. Under these conditions, the organism is no longer able to increase its population but instead begins to make the desired polymer, which it stored for later as use as an energy source.
The bacterial species accumulate the intracellular Polyhydroxyalkanoate granules as energy and carbon reserves inside their cells. The organism is able to produce a quantity of PHB from 30% to 80% of its own dry weight. The organism is then harvested and the polymer is separated out.
What properties does the biopolymer have?
The properties of PHA are quite similar to polypropylene, these similarities are present in their physical and mechanical properties. PHA are thermoplastic, biodegradable, biocompatible and nontoxic. They vary in toughness and flexibility depending on their formulation. They are ductile. They are UV stable in contrast to other bioplastics. The strength and flexibility of the PHA improves with a high percentage of valerate in the material. PHA's are soluble in halogenated solvents. It has good resistance to moisture and aroma barrier properties.