Is pha biodegradable? (3 types of biopolymers)

This blog article shall answer the question of the biodegradability of pha biopolymer.

It shall also cover other areas such as:

  • Properties and applications of pha polymer.
  • Other types of biopolymers.
  • Applications and properties of other types of biopolymers.
  • The eco-friendliness of pha biopolymer.

Is pha biodegradable?

Yes, pha is completely degraded into small non-toxic particles. Pha is made from organic molecules formed in bacteria.

Biodegradation is the breakdown of naturally occurring organic materials into small particles by bacteria and fungi, releasing carbon dioxide and water.

Bacteria, just like most living organisms, use carbon as a source of energy. The basis of biodegradation is for bacteria and fungi to acquire carbon and energy from organic matter.

When bacteria have degraded organic matter to form carbon dioxide and some biomass, they assimilate the biomass, and carbon dioxide is released into the environment.

The assimilated biomass is broken down in the bacterial metabolic reactions to form energy, with carbon as the main source of energy.

To avoid depleting their carbon stores, bacteria convert the carbon into polyhydroxy-alkanoates (PHAs) which act as the storage form of carbon and energy.

When the bacteria have depleted their energy and want to synthesize another one, they break down the polyhydroxy-alkanoate in their metabolic reactions to form energy.

Based on this round of bacterial degradation, it is well to conclude that polyhydroxy-alkanoates are one of the most biodegradable materials in nature.

Researchers have been working tirelessly to come up with biopolymers to reduce plastic in our environment.

Petroleum-based plastics are resistant to microbial degradation and therefore are the most common cause of environmental pollution.

The production of biopolymers is on the rise and sensitization is needed for consumers to embrace these polymers.

How is polyhydroxy-alkanoate (PHA) formed?

Polyhydroxy-alkanoate is formed by bacteria through their metabolic reactions.

The following are the steps to producing polyhydroxy-alkanoate.

  • A culture of microorganisms such as bacterium Cupriavidus necator or Alcaligenes latus is cultured in a medium of glucose or sucrose sugars or vegetable oil.
  • The bacteria colony multiplies and the population increases in many folds.
  • When the population has reached the required level, the composition of the nutrient medium is changed. The biosynthesis of PHA is due to the lack of main elements such as sulfur, phosphorus, and nitrogen or due to the lack of oxygen.
  • Carbon sources such as sucrose and glucose are increased in the media so that PHA is formed as a store for the excess carbon.
  • The PHA polymers are formed and deposited in cells as granules.
  • The bacterial cells are then harvested and disrupted to release PHA which is approximately 80% pure.

Properties of polyhydroxy-alkanoate.

The following are the properties of polyhydroxy-alkanoate polymers.

  • PHA polymers are thermoplastic.
  • It is ductile.
  • It is elastic, depending on its polymer composition, it can be more elastic or less elastic.
  • They are UV stable as compared to other biopolymers.
  • They have low permeability to water.
  • They have low to high crystallinity depending on their composition.
  • They are soluble in halogenated solvents such as chloroform, dichloroethane, and dichloromethane.
  • It has good moisture resistance.
  • Some are brittle and stiff.
  • Some PHA may be elastic.
  • They are biodegradable.

Uses of polyhydroxy-alkanoate.

The following are the uses of polyhydroxy-alkanoate polymers.

  • They are used to make packaging materials.
  • They are used in making sutures, suture fasteners, tacks, and staples.
  • They are used in making bone plates and bone plating systems.
  • Used in making cardiovascular patches.
  • Used in making nerve guides.
  • Used in making tendon repair devices.
  • Used in making hemostats.
  • Used in making ocular cell implants.

What are the types of polyhydroxy-alkanoates?

There are different types of polyhydroxy-alkanoates depending on the bacterial species or the nutrient media used to make them.

Polyhydroxybutyrate(PHB).

This is a type of polyhydroxy-alkanoate belonging to the polyester family of organic polymers.

Poly-3-hydroxybutyrate is the most coon type of PHB polymer. 

PHB is produced by bacterium species such as methylobacterium rhodesianum, Bacillus megaterium, and Cupriavidus necator.

It is produced mostly from glucose and starch molecules.

Properties of poly-3-hydroxybutyrate.

  • It is water-soluble.
  • It has a good UV resistance.
  • It has poor acid and base resistance.
  • It has good oxygen permeability.
  • It is soluble in solvents such as chloroform and other halogenated compounds.
  • It is biocompatible.
  • It has a high melting point of 175⁰C.
  • It has high tensile strength.
  • It sinks in water, hence the anaerobic degradation in water sediments.
  • It is non-toxic.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate).

This is a polymer of the class polyhydroxybutyrate. It is commonly known as PHBV.

It is produced by the polymerization of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid monomers.

Properties of PHBV.

The following are the properties of PHBV.

  • It is a brittle polymer.
  • It has low impact resistance.
  • It has low thermal stability.
  • It is biocompatible.
  • It is nontoxic.
  • It is thermoplastic.

The polyhydroxy-alkanoate polymers belong to the class of polyesters.

Polyester is one of the most popular polymers used in industries and households.

Polyester.

This is a polymer that contains a repeat of ester groups.

It is also called polyethylene terephthalate.

Properties of polyester plastic.

The following are the properties of polyester.

  • It is inert.
  • It is a strong and hard material.
  • It is durable.
  • It is resistant to microbial attack.
  • It is lightweight, and hence easy to carry.
  • It is fully recyclable.
  • Uses of polyester.

The following are the uses of polyester plastic.

  • It is used in making fabrics for knitting shirts, pants, jackets, bed sheets, blankets, upholstery, and hats.
  • It is used in the reinforcement of car tires.
  • Making conveyor belts.
  • Making safety belts.
  • Used as cushioning material in pillows.
  • Used in making liquid crystal displays.

What are the comparisons between synthetic polymer and organic polymer?

There are several advantages and disadvantages of using synthetic and organic polymers.

The choice is dictated by the purpose of the polymer.

  • Synthetic polymers are obtained from petrochemicals while organic polymers are obtained from plants and animals.
  • Synthetic polymers are non-biodegradable while organic polymers are biodegradable.
  • Synthetic polymers are very durable while organic polymers are long-lasting but are eventually susceptible to microbial degradation.
  • Synthetic polymers are recyclable and mostly non-renewable while organic polymers are mostly non-recyclable but are renewable.
  • Most synthetic polymers are non-biocompatible while organic polymers are biocompatible.
  • Organic polymers are carbon-based while synthetic polymers do not contain carbon.
  • Processing of synthetic polymers releases toxic chemicals into the environment while processing of organic polymers does not release toxic chemicals.

Is polyhydroxy-alkanoate eco-friendly?

Yes, PHA is made from organic materials such as glucose and sucrose. It is biosynthesized by bacteria and as a result, is susceptible to digestion by the bacterial enzymes through the process of biodegradation.

According to a study on the biodegradation of PHA, the rate of biodegradation of PHA depends on its number of polymers.

Poly-3-hydroxybutyrate which is a type of polyhydroxy-alkanoate sinks in water where it undergoes anaerobic biodegradation. This makes the polymer an ideal material for environmental conservation because it does not pollute the environment.

Conclusion.

This article has covered the biodegradability of polyhydroxy-alkanoate and its suitability for the environment.

PHA is one of the most biodegradable polymers since it is produced by bacteria, which are the primary agents of biodegradation.

Research is still ongoing to improve the quality of biopolymers. There is research on the production of genetically modified bacteria that would produce biopolymers that have the same physical properties as synthetic polymers, to improve durability and increase the number of applications.

This article has also covered some other areas.

  • The types of polyhydroxy-alkanoates.
  • Properties and uses of polyhydroxy-alkanoate.
  • The biosynthesis process of PHA.
  • The comparison between organic and synthetic polymers.

For any questions or comments please use the comment section below.

Frequently Asked Questions (FAQs): is PHA biodegradable?

Does PHA biodegrade?

Yes, PHA is one of the most biodegradable organic materials because it is produced by bacteria.

Does PHA degrade in landfills?

Yes, PHA degrades in landfills and composts. It also degrades in the water bodies and therefore does not pollute either the soil or water.

What does PHA biodegrade into?

PHA degradation produces different products depending on the environment.

In the presence of oxygen, PHA undergoes aerobic degradation to produce water and carbon dioxide.

In the absence of oxygen, PHA undergoes anaerobic degradation to produce carbon dioxide and methane.

Citations.

Lu, Jingnan; Tappel, Ryan C.; Nomura, Christopher T. (2009-08-05). “Mini-Review: Biosynthesis of Poly(hydroxyalkanoates)”. Polymer Reviews. 49 (3): 226–248. doi:10.1080/15583720903048243. 

Bhubalan, Kesaven; Lee, Wing-Hin; Sudesh, Kumar (2011-05-03), Domb, Abraham J.; Kumar, Neeraj; Ezra, Aviva (eds.), “Polyhydroxyalkanoate”, Biodegradable Polymers in Clinical Use and Clinical Development, John Wiley & Sons, Inc., pp. 247–315, doi:10.1002/9781118015810.ch8,

Ackermann, Jörg-uwe; Müller, Susann; Lösche, Andreas; Bley, Thomas; Babel, Wolfgang (1995). “Methylobacterium rhodesianum cells tend to double the DNA content under growth limitations and accumulate PHB”. Journal of Biotechnology. 39 (1): 9–20. doi:10.1016/0168-1656(94)00138-3.

Vert, Michel; Doi, Yoshiharu; Hellwich, Karl-Heinz; Hess, Michael; Hodge, Philip; Kubisa, Przemyslaw; Rinaudo, Marguerite; Schué, François (11 January 2012). “Terminology for biorelated polymers and applications (IUPAC Recommendations 2012)”. Pure and Applied Chemistry. 84 (2): 377–410. doi:10.1351/PAC-REC-10-12-04. S2CID 98107080.

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