From Bugs to Plastics: The journey of Bioplastic production and biodegradation of synthetic plastics via the help of bugs

With the increase in processed, synthetic goods and the increased packaging of industrial items, there has been an immense increase in the use of plastics as well. According to pollution control, approximately 380 million tons of plastic is produced every year, and this leads to all kinds of environmental as well as health hazards (Plastic Pollution Facts ). 

What is synthetic plastic made up of and what makes them non-degradable?

The main ingredient used for the production of plastics is petroleum-based products which include crude oil, natural gas, and coal. The monomers (ethane and propane) released from the heating of these fossil fuels once again form polymers (polyethylene and polypropylene) (Baheti). These long chains are responsible for giving the stretch to the plastic material and making it durable for more than 100 years. Moreover, microbes as well as insects are not able to consume these complex polymers at a faster rate and require special conditions which will be discussed below.

Nevertheless, with time, and modifications in biotechnological methods, scientists have come to know about various methods for plastic degradation and bioplastic production which light up a beacon of hope for bioremediation and eventually environmental betterment.

Synthetic plastic degradation:

• By biotransformation of microbial products:

One of the most essential applications of Biochemical Engineering is biotransformation, which is defined as the modification of chemical compounds with the help of biological processes happening in living organisms (Chemistry). It is used in such a way that different plastic materials are provided to the microbes, which aid in their growth and development, and later onwards at the stage when their growth rate decreases, they form products in the form of biotransformants. At first, this brilliant tool was only used for the production of drugs, however now it is also playing its role in bioremediation. Various products from plastic polymers have been produced through the biotransformation of microbes. For example, polyethylene terephthalate (PET), is a plastic polymer that is degraded with the help of Yarrowia lipolytica to produce glycolic acid (Adriano Carniel, 2023), an industrially important product.

• By enzyme activity:

The biocatalysts “enzymes” are also extremely useful for the degradation and breakdown of plastics. The hydrolytic enzymes cutinase, lipase, and PETase are a few common enzymes that get this job done. These enzymes belong to the Hydrolases group and as the name suggests, are responsible for breaking down chemical bonds in the presence of water molecules and hence degrading plastic (Jyoti Kaushal, 2021). Furthermore, fungal enzymes responsible for the breakdown of lignin and cellulose have also been proven to degrade plastics such as polyethylene (PE), Polyvinyl Chloride (PVC), polyurethane (PUR), and PET (Marta Elisabetta Eleonora Temporiti, 2022).

• Biodegradation in landfills:

One of the easiest methods of plastic degradation is the landfilling method. Although plastics in landfills might take up a lot of space, however, they can be degraded by the microbes naturally present in the landfills without any extra effort. Microbes including Escherichia coli, Bacilli, and Pseudomonas are present in the landfills. Pseudomonas species are found to degrade polyethylene, polyurethane, polystyrene, etc. into simple monomeric form (R A Wilkes, 2017). Furthermore, the UV radiation reaching the landfills also breaks down the polymeric structure of plastics as most plastics tend to absorb heat and high-intensity radiation. These radiations tend to excite the electrons of the polymeric structures and hence are a means of photo-degradation (Irena Wojnowska-Baryła, 2022).

Bioplastic synthesis:

The alternative and more environment-friendly option of synthetic plastics is bio-plastic. Not only are bio-plastics good for the environment but are also cheap to produce. We have discussed a few types of bug-based bioplastics below:

• By dead insects and exoskeleton:

To find a good source to produce bio-plastics, it is necessary to take raw materials that contain a rich source of carbohydrates. For the past few years, environment enthusiasts have been using insects for the production of bio-plastics as their exoskeleton is made up of chitin (a complex polysaccharide). Some insects shed their chitin layer with their growth whilst some do not and therefore whole of the insects are used to make bioplastics. Moreover, the cuticles are also chitinous and stretchable which also are a good means of bioplastic production (What are insect-inspired bioplastics?, 2017). A few examples of insect-based plastics being made these days are Coleoptera plastics and Shrilk.

·         Biotransformation via the help of microorganisms:

Apart from the degradation of synthetic plastics, biotransformation also plays a role in bio-plastic production. Environmental and genetic scientists are working on using engineered microbes to produce bio-transformed chemicals suitable for bio-plastic production. The main principle of this biotransformation is to use a simple sugar as a substrate which will be transformed into a complex polysaccharide. One of the latest researches involves the transformation of glucose to dihydrocarvide* (DHCD) which is a shape-memory polymer with the help of engineered microbes (Adriano Carniel, 2023).

*Dihydrocarvide is a derivative of the parent molecule dihydrocarveol, and this biopolymer is a recent breakthrough made possible through E. coli engineering.

Conclusion:

Plastics, an essential part of everyone’s daily life, pose some very serious environmental threats as well. The introduction to bioplastics has led to a vast world for the production of easily degradable plastics and research is still taking place for opening the doors of new opportunities. Additionally, because they are cheaper and simpler to produce than synthetic plastics, bioplastics are a fantastic solution for enterprises. We can help create a world where plastic pollution is reduced, ecosystems flourish, and we move to achieve a sustainable balance between human needs and environmental health by lobbying for additional developments in bioplastic technology.

References

Adriano Carniel, A. G. (2023, March 10). Biotransformation of ethylene glycol to glycolic acid by Yarrowia lipolytica: A route for poly(ethylene terephthalate) (PET) upcycling. Biotechnology Journal, 18(6).

Baheti, D. P. (n.d.). How Is Plastic Made? A Simple Step-By-Step Explanation. Retrieved from British Plastic Federation: https://www.bpf.co.uk/plastipedia/how-is-plastic-made.aspx#:~:text=Plastic%20can%20either%20be%20'synthetic,bacteria%20and%20other%20biological%20substances.

Biotransformation. (n.d.). In L. Chemistry, Toxicology.

Gabriel A. Ascue Avalos, D. H. (2018). From Bugs to Bioplastics: Total (+)-Dihydrocarvide Biosynthesis by Engineered Escherichia coli. CHEMBIOCHEM, 20(6), 785-792.

Irena Wojnowska-Baryła, K. B. (2022). Plastic Waste Degradation in Landfill Conditions: The Problem with Microplastics, and Their Direct and Indirect Environmental Effects. International Journal of Enviornmental Research and Publix health.

Jyoti Kaushal, M. K. (2021). Recent insight into enzymatic degradation of plastics prevalent in the environment: A mini-review. Cleaner Engineering and Technology.

Marta Elisabetta Eleonora Temporiti, 1. L. (2022). Fungal Enzymes Involved in Plastics Biodegradation. Microorganisms.

R A Wilkes, L. A. (2017). Degradation and metabolism of synthetic plastics and associated products by Pseudomonas sp.: capabilities and challenges. Applied Microbiology.

What are insect-inspired bioplastics? (2017, October 13). Retrieved from Barbour product search: https://www.barbourproductsearch.info/what-are-insect-inspired-bioplastics-blog000393.html

 

 By: Syeda Uzma Raza