What is PHA bioplastic? History and uses.

HomeBioplasticsWhat is PHA bioplastic? History and uses.
Bioplastics
18/09/2021
By: Magic Genetics
Tags: , ,
Uses of PHA as biodegradable plastic.

Biodegradable plastic called PHA, which stands for Polyhydroxyalkanoate, is a type of polymer produced by bacteria. Therefore, it can easily disintegrate in the environment. Certain bacteria produce PHA when they are under stressed conditions. PHA can be used in many different applications. They can also be modified and improved to suit our needs. Each year more and more types of bacteria producing PHA are identified.

In present times we use plastic almost everywhere and therefore it is important to replace plastic which is non-degradable with biodegradable, such as PHA. Plastic is not only used to produce plastic bags, disposable forks, spoons or PET plastic bottles. Very important field is also the medical and pharmaceutical field. There is also a possibility to use PHA in agriculture (Tan et al., 2019). Decomposition in nature of non-biodegradable plastics can take between hundreds of years to thousands of years. It is also one of the largest sources of pollution in oceans. Plastics that are not disposed properly pollute not only water but also air and soil. Some plastics are burned and this produces toxins in the air which can cause respiratory problems but also neurological diseases. Also animals suffer when they eat pieces of plastic and die due to this. Plastic can degrade by ultraviolet light from the sun into very small particles called microplastics. They are also dangerous because they are too small to be collected but they do harm to animals. It is predicted that by 2050 there will be more plastic in the oceans than fish (Kaza et al., 2018). All these problems show how important it is to stop producing non-biodegradable plastics and switch to biodegradable plastics. PHA is one of these options. 

Microplastics in water

What are microplastics?

  • Small pieces of plastic from disintegrated bigger plastic objects. 

How does microplastic affect the ocean?

  • Aquatic life and birds can mistake microplastics for food. Also microplastics can absorb harmful chemicals and they can contaminate water or make harm to aquatic animals.

Toxic air

Toxic air can cause problems with babies’ brain development with lifelong implications, children’s learning and development. Pollutants are harmful for babies’ lungs development (Unicef, 2017). For adults toxic air can cause respiratory problems and even be a cause of death.

Is PHA a biodegradable plastic? 

Yes PHA is biodegradable because it is created naturally inside bacteria and also PHA plastic can be degraded naturally by microorganisms. The photo below shows bacteria with PHA granules inside their cells. PHAs are synthesized by many different bacteria as carbon and energy storage capsules.

PHA was discovered for the first time in 1926 in one type of bacterium called Bacillus megaterium. First efforts to use PHB (a type of PHA) commercially was in the 1950s. However, the process of PHB production was not so easy and unprofitable. Later in 1970 a company called Biopol started production of PHA. Later other companies also started the production process. Since this time there have been over 150 different types of PHAs discovered. PHA plastics can also be modified in order to make them more stiff or brittle. 

PHAs are not only biodegradable plastics but also thermoplastics. Their melting temperature is between 50°C and 180°C. PHAs molecules are not toxic and can be used in medicine but it is necessary to check if they are biocompatible. It means that when they are introduced to a human’s body they should not cause severe immune reactions. 

What can PHA plastic be used for

Medical applications:

  • Cardiovascular tissue engineering – PHAs can be used instead of synthetic materials. Bioplastics can be used to repair or replace damaged, diseased, or malfunctioned blood vessels. Scaffolds in tissue engineering can also be made out of PHAs. They get covered with cells and can be implanted for a few months. No medical problems or inflammatory responses were observed. Heart valves can also be produced using PHAa.
  • Bone marrow scaffolds. They can be used for patients with bone loss. Biodegradable scaffolds can be covered with bone marrow cells. With time the biodegradable scaffold will disintegrate and bone marrow cells will stay in the suitable place. 
  • Cartilage repair – bioplastic can be used in cartilage tissue engineering to regenerate cartilage.
  • Biodegradable plastic can also be used in eye disorders to create scaffolds used in eyelid reconstruction.
  • PHAs can be used as scaffolds for nerve regeneration.
  • Wound management, skin regeneration – wound dressing or scaffolds. PHAs are also a good material to be used in reconstructive medicine to treat injured skin. Special scaffolds can be created that are comparable to those of human skin. Special cells can be seeded on these scaffolds. They can be used as a matrix material for skin tissue engineering. Such scaffolds can be used in difficult contours of the body. Also wounds covered with specially prepared film can heal more quickly. The membrane can also reduce inflammation. 
  • From the 1990s PHAs were studied in drug delivery systems. Therapeutics can be delivered for prolonged release. As a natural polymer they are biodegradable and biocompatible. 
  • New tissue formation or regeneration.
  • Development of artificial esophagus.
  • Biodegradable plastics can be used as absorbable fibers, surgical meshes, repair patches, suture material, suture fasteners, screws, bone plates, bone filling augmentation material and many more.
  • PHAs are also great to be used in pediatric applications because when they are applied for children they do not hinder growth.
  • They can also be used for blood vessels repair, heart valve scaffold.
  • In cancer therapy and controlled drug delivery. 
  • Orthopedic applications of PHAa include bone accumulation or maintenance of osteoblast phenotype.
  • Cartilage engineering

Non-medical applications

  • Packagings that can be degraded into carbon dioxide and water by microorganisms. From PHA bottles, bags and films can be produced. Already in the 1980s Biopol started experimenting with packagings made of PHA. First packagings were shampoo bottles, parts of sanitary products for women and diapers that created moisture barriers, shopping bags, containers, cups, medical surgical garments, upholstery, carpets. 
  • Fiber material which possibly could be used in textile industry
  • Biofuels which can be produced low cost
  • PHB can be used as paper finishing to coat paper as they are water insoluble, can create oxygen barrier and are UV resistant. They also have excellent film-forming properties. Paper covered with PHB becomes more water resistant. 
  • Agriculture applications of PHA as a carrier for targeted and controlled delivery of pesticides to soil. PHA becomes later degraded in the soil by microbes. Thanks to this method herbicides do not impact so much non-targeted species and also reduce the need for repeated applications. PHAs can help with controlling bacterial pathogens. Addition of PHB in the feed of prawns reduced the amount of bacteria and therefore the survival rate of the prawn larvae is higher and their development is better. 
  • Silver nanoparticles which are known for their antibacterial properties can be stabilised by addition of PHAs. Without it they are not stable and therefore their use is limited. 

(Singh Mathuriya and Yakhmi 2017)

References:

Author of the post Magic Genetics

About Magic Genetics

Welcome to Magic Genetics

Other posts by this author