Biopolymers are polymers that those that are made from living things and can be broken down by micro-organisms when released into the environment. Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate produced by a microorganism called Alcaligenes Eutrophs. The bacterial culture is given abundant nutrient for rapid replication. Nutrient supply is then drastically reduced and the bacteria converts the available food into energy storage. This is produced in the form of PHB. PHB is then harvested and could be used. PHB has the potential to replace polypropene.
Polypropene is used in a variety of applications including packaging, textiles, stationery, reusable containers and cutlery, laboratory equipment etc. Although PHB has a different molecular structure to polypropene, it has remarkably similar physical properties which can be used as wrapping or packaging material also. PHB consists of a long carbon chain, indicating it has a rather strong dispersion force because of high molecular weight. Hence it has a considerably high boiling and melting point. Its tensile strength is also close to that of polypropylene, allowing it to be made into reusable containers.
It has minor chain stiffening which contributes to its moderate rigidity which makes it suitable for plastic cutlery. It is non-polar and will not dissolve in polar substances such as water and is relatively resistant to hydrolytic degradation. This differentiates PHB from other biodegradable plastics which are either water soluble or moisture sensitive. This property also allows PHB to be made into packaging material. PHB is biocompatible and hence is suitable for medical applications. While polypropylene floats in water, PHB sinks, facilitating its anaerobic biodegradation in sediments implying that it will be more eco-friendly.
When melted, it is less sticky, making it a potentially good material for clothing in the future. More importantly, the polymer is non-toxic and can be used safely. Although PHB is not produced in a large scale industrially, its potential uses are immerse. PHB is renewable because it can be synthesised by micro-organisms and replenished in a short period of time. This can reduce our dependency on plastics that are derived from crude oil, a non-renewable source which will eventually be depleted. It is biodegradable and could rapidly disintegrate in the environment.
Its biodegradable nature implies a resolution to reducing white pollution and issues of littering food packagings, medical supplies etc. However, PHB production is more expensive and time-consuming. Time is needed for cultivation, production and harvesting. Large amounts of funding is needed for nutrient supply and other resources such as monitoring equipment. Hence, it is not yet economic to mass produce PHB for use PHB has great potential and is eco-friendly, a possible renewable alternative if an economical method of production is introduced.