University of Helsinki
During the span of the last century plastic has become an indispensable part of our daily lives. Have you ever wondered what happens to all that plastic we use daily? Plastic and more specifically PET, which is short for polyethylene terephthalate is a useful material due to its flexibility, low moisture absorption and dimensional stability. However it also has downsides, mostly when it comes to recycling and environmental impacts. Plastic waste accumulation has become a global threat that requires immediate action. Imagine if we ignore this plastic problem—it could mess up our health and harm all living things. Due to the material’s non-biodegradable nature finding a solution to the plastic pollution crisis is a tricky matter. The method with possibly the most potential as of now, could be biodegradation using the plastic-eating bacteria.
Polyethylene terephthalate is a petroleum-based polymer composed of monomeric residues of terephthalic acid (TPA) and ethylene glycol (EG) bonded via ester linkages which greatly contributes to the stability of the molecules. This property of PET makes it a complex material to recycle. It’s not as easy as tossing it in the blue bin. There are a few methods that have been developed for that purpose. There is physical recycling which involves processes like grinding and melting, and then there is also chemical recycling that employs techniques like hydrolysis or glycolysis. However, these methods have major drawbacks, as they consume great amounts of energy. They also involve the use of harsh chemicals and are not suitable to be utilized on a larger scale. Moreover, these processes can be harsh on our planet, sparking some eco-concerns. That’s why we’re on the hunt for friendlier and greener alternatives.
In response to the limitations of traditional methods, biodegradation emerges as a cleaner and gentler alternative. It utilizes the ability of certain bacteria to enzymatically degrade plastic, offering a more sustainable solution for plastic pollution. It’s just nature’s way of breaking down plastic into tiny, recyclable bits. The bacteria discovered to possess plastic eating abilities is Ideonella skaiensis. It opens new possibilities for harnessing biodegradation as an effective means of plastic recycling. Ideonella sakaiensis produces two enzymes crucial for this process, IsPETase and MHETase. They break down PET into smaller pieces, so called monomeric forms through enzymatic hydrolysis. The bacterium, when coming in contact with the PET surface, binds to it, which triggers the release of the enzymes. The enzymes are believed to be transported through the extracellular appendages of the bacterium. IsPETase breaks PET into MHET and TPA and during the second step of the process MHETase further decomposes MHET into TPA and EG (ethylene glycol). These major products that can be further processed to make new plastic polymers, which makes biodegradation a very advantageous method of recycling.
Imagine a world where plastic is recycled by tiny creatures instead of harsh methods. That’s the potential of biodegradation compared to traditional recycling! It stands out for its ecological compatibility. The method doesn’t require the involvement of harsh chemicals or great amounts of energy, instead it utilizes the natural abilities of bacteria to metabolize plastic. Using naturally occurring organisms can offer cost advantages in terms of raw material and process simplicity. However, the limitations of this recycling method must also be addressed. Research still needs to be done when it comes to scaling up biological processes, including microbial culture limitations and optimizing conditions for large-scale applications. There are some challenges on the horizon, but diving into this research is like unlocking a more eco-friendly and energy-saving way to manage our waste. Seems totally worth it, right?
References:
Kaur, K. et al. (2023) Recent Advancements and Mechanism of Plastics Biodegradation Promoted by Bacteria: A Key for Sustainable Remediation for Plastic Wastes. Biosciences, biotechnology research Asia. [Online] 20 (1), 1–12.
Maja Kubik