Download Use available evidence to gather and present data from secondary

Lan Gao
Use available evidence to gather and present data from secondary sources and
analyse the properties in the recent developments and use of a named
biopolymer. This analysis should name a specific enzyme or organism used to
synthesise the material and an evaluation of the use of potential uses of the
polymer used based on their properties.
Poly (hydroxyalkanoates) or PHAs are a group of biopolymers produced from glucose
using a bacterial catalyst. The property of the polymer produced depends on the
bacterial strain and the conditions under which the fermentation process takes place.
The polymers can be either thermoplastics or elastomeric plastics. These polymers are
originally used by the bacteria for energy storage but have been found to have
potential to replace the oil based thermoplastics. PHA’s are more desirable than
thermal plastics as they are renewable resources and do not have the same disposable
problems as thermo plastics due to their ability to biodegrade.
The first PHA to reach the market was Polyhydroxybutyrate or PHD. It is synthesised
by using the microbes Alcaligenes eutrophus or Bacillus megaterium. The bacteria are
fed on glucose and can create polymers of up to 80% of their dried weight. These
bacteria have undergone genetic modification in order to increase the yield of
polymer. This has resulted in the price of production falling from $800 a pound in
1980’s to <$1a pound today. The glucose used is usually wastes from places such as
sugar mills and milk processing. By controlling the carbon sources of the bacteria
changes the properties of the given polymer. Originally the first PHB produced was
too brittle to be of much use. However it was discovered that when propionic acid was
added to the bacteria’s diet a new polymer was produced which was far more flexible.
Polyhydroxybutyrate-hydroxyvalerate or P (HB-HV) is formed with the use of
Alcaligenes eutrophus and is fed precise proportions of glucose and propionic acid.
By making the polymer more flexible it has expanded the available uses of this
polymer.
PHA’s are marketed under the name Biopol. These polymers have an elasticity of 5%
to >10000% elongation at break, UV stability, water stable yet biodegradable in
marine, soil, compost and waste treatment environments, excellent film forming
properties from aqueous latex and environmentally compatible. PHA’s can be used as
polymer performance enhancers, non-woven fabrics, film and fibre, adhesives and
coatings, binders for metals, biodegradable packaging and water resistant coatings.
They are increasingly popular due to two major characteristics that they posses.
PHA’s are both biocompatible and biodegradable. Due to this biocompatibility they
can be used in medical application such as capsules for controlled drug release,
surgical sutures, bone plates and wound are without the fear of a reaction from the
patient or the polymer being toxic. They have the potential to be used a structural
materials in personal hygiene products and packaging applications. Although the cost
of PHBV has fallen it is still far more expensive than normal petroleum based
polymers. The fact that PHA’s are biodegradable makes them perfect for disposable
packaging. It is currently used in cosmetic containers and commercial films and paper
coatings. There is also researching to creating a biodegradable fishing net which will
lead to decreased instances where sea creatures are caught in disposed nets.