Our Motive
Through our project we aimed to resolve an everyday issue observed in our local community. After taking a look around our city, Thessaloniki, we realized that one of the issues we should be concerned with is pollution. Further research showed that this also applies to the majority of big cities worldwide. One significant factor of pollution is plastic and more specifically the process of degrading it, which is time-consuming, expensive and harmful to the environment. For this reason, we decided to utilize synthetic biology in order to come up with an alternative improved solution, in hope of reducing the scale of plastic pollution.
The Problem of Plastic
It is a widely known fact that plastic is a major environmental hazard that is causing significant harm to our planet and its inhabitants. In particular, plastic waste often ends up in our oceans and waterways, where it can harm or kill marine life. Furthermore, plastic pollution can affect human health by contaminating our food and water sources. Currently, plastic recycling rates are low and much plastic waste ends up in landfills or incinerated, releasing toxic chemicals into the environment.
Our Solution: Utilizing PETase
What's PET?
In 2016, a bacterium, Ideonella sakaiensis, discovered in Japan showcased the ability to break down tetra-phthalate plastic (PET), the most common type of plastic. Its ability was attributed to an enzyme, named PETase, capable of biodegrading one of the most widespread types of plastic, PET. We soon identified the limiting factors in the biodegradation process and realized that we could accelerate its slow rate by fusing the PETase enzyme with another helper enzyme that would assist in the biodegradation process.
Overview of Our Project
Our goal was to accelerate the rate of biodegradation of PET plastic using a very common synthetic biology technique called enzyme fusion, making our suggestion for confronting plastic pollution worldwide not only promising, but also affordable and accessible, hopefully enough to encourage incorporation in the plastic industry. The biodegradation process of PET plastic by PETase can be summarized in two steps. Firstly, PETase breaks down PET plastic into 3 components: BHET [Bis(2-Hydroxyethyl) terephthalate], MHET [Mono-(2-hydroxyethyl)terephthalic acid] and EG (Ethylene glycol). Ideonella sakaiensis also contains an enzyme called MHETase, which then breaks down MHET to TPA (terephthalic acid) and EG, the former of which can be used for the production of sustainable plastic and both of which can be used by the bacterium for metabolic processes.
Figure 1. Biodegradation of polyethylene terephthalate (PET).
After careful evaluation of candidate cutinases, we chose to take the cutinase from the fungus Fusarium solani due to the following reasons:
- It is closely related to PETase in terms of plastic biodegradation property.
- More readily available than others with similar properties.
- Common points in ideal optimum temperature and pH: 25-40°C (Cutinase), 25-30°C (PETase). 8.0 (cutinase), 8.0 (PETase).
Finally, we formulated the base sequence of our final product, containing the sequence of both enzymes with the sequence of a linker in between them, all of which would be placed in a plasmid to enable expression in a host bacterium.
References
1. Author links open overlay panelBaotong Zhu 1 et al. (2021) Enzyme discovery and engineering for Sustainable Plastic Recycling, Trends in Biotechnology. Available at: https://www.sciencedirect.com/science/article/pii/S0167779921000408 (Accessed: 21 June 2024).
2. Igem 2021: Designing better enzymes to break down plastic: Carl R. Woese institute for genomic biology (2021) iGEM 2021: Designing better enzymes to break down plastic | Carl R. Woese Institute for Genomic Biology. Available at: https://www.igb.illinois.edu/article/igem-2021-designing-better-enzymes-break-down-plastic (Accessed: 21 June 2024).