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Organisms That Eat Plastic - How We Can Save Our Oceans Before It Is Too Late.

The problem with plastic in our oceans.


You've almost certainly heard that plastic is entering our seas at an alarmingly fast rate and it's causing problems with the food we eat, crucial ecosystems and our atmosphere.


90% of plastics are made from fossil fuels, that are heated through a process called cracking to make ethylene and propylene monomers. These olefins are polymerised, along with other materials, to form polymers which can then be moulded into the products that we know and love. Hence, the word plastic comes from the Greek word 'plastikos' meaning 'to form'.


It is important to note the hugely beneficial impact plastic has had on our society, due to its durability and diverse uses that have helped us to grow into the world we see today. However, the process of turning refined fossil fuels into useable polymers is shockingly destructive. 2.5 tonnes of carbon dioxide is released per 1 tonne of plastic produced. Yet, 380 million tonnes of plastic is being produced per year - that's 2.6 million tonnes of carbon dioxide being produced daily by plastic production alone! This emission of fossil fuels is of course, trapping heat in the earth's atmosphere and causing climate change through the 'greenhouse effect'.


Not only this, but there are currently 5.25 trillion pieces of plastic in our oceans that are harming wildlife, such as the 100,000 marine animals that are killed each year due to plastic pollution or the 500 'dead zones' where once thriving ecosystems can no longer exist.


But how does any of this affect you?


To reiterate my earlier point, climate change will affect all of us. Clean air, sufficient food and safe drinking water are all at risk, meaning increases in disease and malnutrition. In fact, you have probably already been affected by microplastics in your diet. 1 in 3 fish caught for human consumption contain plastic, causing each of us to eat an average of 100,000 microplastics a day. These microplastics are toxicological vectors, meaning they absorb harmful chemicals from the environment, such as pesticides and heavy metals, and carry them into our bodies. Furthermore, studies have shown microparticles of polyamide (nylon) can cause endocrine (hormonal) disruption when inhaled - a possible explanation for increases in obesity and fertility issues.


Now for some more hopeful news...


Scientists have discovered that a blue mussel species called Mytilus edulis consumes microplastics and excretes them in their faeces - a much easier substance to remove from the water. The faeces can be collected, as it is dense so sinks to the ocean floor, and potentially converted into biofilm, used for bioremediation (treating oil spills and contaminated water with bacteria, archaea and fungi). These mussels also don't retain the microplastics so are still safe to eat!


Sadly, there are some quite serious flaws in this plan. Evan Ward, a University of Connecticut environmental physiologist, expressed that it would require around 2 million mussels filtering water consistently for 24 hours a day to clean the water in a single New Jersey bay. This would cause huge disruption for the ecosystems and food chains in areas being treated and is not cost-effective or efficient considering how pressing the plastic crisis is. Penelope Lindeque, an ecologist at the Plymouth Marine Laboratory who led the research, emphasised that although she is hopeful about this investigation, "we need to be stopping plastics at the source” and stressed that we, humans, need to fix the issues we have created, not mussels.


Yet it doesn't stop at mussels...


A Spanish scientist named Dr. Federica Bertocchini found some worms destroying her beehive when cleaning it out. She removed the worms and threw them in a plastic bag. Not long later, she noticed holes in this bag and upon further inspection, realised that the worms were eating the plastic! These worms are a species called Galleria mellonella and their larvae can consume and digest polyethylene, which still is the most widely used plastic.


So, how do they do it?


Following the initial discovery, they introduced a paste composed of crushed caterpillars to a sample of polyethylene film and allowed the larvae to consume it. This led to the emergence of new signal peaks during an infrared spectrometer scan. Bertocchini and her research team attributed these peaks to the production of ethylene glycol, a decomposition by-product that likely originated from an enzyme within the worms' gut microorganisms.


Scientists have found this enzyme to be PETase. PET or polyethylene terephthalate is the most abundant plastic in the polyethylene group. Most PET is crystalline making it recalcitrant - i.e. very difficult to degrade. The enzyme PETase breaks down PET into its monomers (terephthalic acid and ethylene glycol). However, naturally occurring PETase works very slowly and only in specific conditions, leading scientists to try to improve the enzyme in the lab.


Many research teams from across the globe have been trying their hand at improving PETase. The most notable outcome was from researchers at the University of Texas. They created FAST-PETase, a version of PETase that has five mutations, allowing it to work at between 30 and 50 degrees Celsius. They describe it as “functional, active, stable and tolerant,” and it has been confirmed to break down a total of 51 PET-based items within a week. In certain instances, it requires just a matter of hours or days. It's no wonder that they have patented this technology and are looking for commercial partners!


These aren't the first instances of plastic-eating organisms.


Researchers have been pinpointing plastic-degrading microbial species since the 1990s. Investigations of various algae species have unveiled their ability to thrive on the surfaces of various plastic types, causing partial degradation. Additionally, we are aware of at least 28 fungal species that can utilize plastics as a source of carbon or energy.


However, the more recent and exciting progression in these discoveries, is that we may now have the drive, resources and technology to harness the power of these organisms. A great example of how we can benefit from science that nature has been using for decades.


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