Ideonella sakaiensis: A Novel Method of Recycling Plastic
Ideonella sakaiensis: A Novel Method of Recycling Plastic
Natalie Chin
Thomas Jefferson High School for Science and Technology
This article was originally included in the 2019 print publication of the Teknos Science Journal
The highlight of every aquarium is the underwater tunnel. With blue lights casting wavy shadows on guests and fishes swimming alongside, these tunnels give a sneak peak of the magical ocean floor. But this beautiful image is a mere illusion. In reality, trash lines the seafloor, concealing pristine sand, and plastic bags flow through currents, entangling and suffocating unsuspecting marine life. Pollution has gone rampant and our oceans are paying the price [2]. The most harmful substances in circulation are plastics, which are extremely hard to degrade, yet are ubiquitous. To combat this problem, my Oceanography Lab senior research project aims to find a solution using microbes and genetic manipulation. From afar, bacterial films seem underwhelming, but on the microscopic level, thousands of complex and interconnected chemical reactions occur that can degrade even the most robust substances. Molecules invisible to the naked eye may hold the key to solving humanity’s largest polluter.
Rather than decomposing, plastics break into smaller pieces that seep into the soil, atmosphere, and water. Plastics entered circulation in 1907, which means that every piece of plastic manufactured still exists today. Every boba straw, every water bottle, and every grocery bag remains and is most likely in our oceans [4]. Microplastics are tiny pieces of degraded plastic, plastic beads, and synthetic fibers that are often mistaken for food and ingested by algae. When marine organisms consume these algae, they absorb microplastics at concentrated volumes, resulting in the bioaccumulation of microplastic throughout the food web. The amount of microplastics soon reach toxic levels, and when humans eat seafood, we are harmed by the high doses of plastic poisoning. Moreover, macroplastics like fishing gear and bottle caps are equally dangerous to marine organisms, with many getting entangled and suffocated by this larger plastic debris [7].
Currently, recycling factories are the only viable approach to managing large quantities of plastic waste. However, the long-term sustainable solution lies not in heavy machinery, but in microbial life. Discovered in a Japanese plastic bottle recycling factory, Ideonella sakaiensis is a species of bacteria able to break down polyethylene terephthalate (PET) plastics into environmentally-friendly compounds [10]. PET plastics are one of the most common types of plastics, found in water bottles, food packaging, detergent containers, tennis balls, and many more household items. The bacteria degrades the material through an enzyme called PETase, which has a flexible active site where plastics can bind to the catalytic molecule. The flexibility is a major contributor to the enzyme’s ability to facilitate chemical reactions in charge of degrading PET into environmentally friendly compounds [3]. I. sakaiensis uses PET as its main food and carbon source and converts the material into energy to sustain itself [8]. This discovery has huge implications for dealing with the increasing pollution, as it is a cost-efficient method of degrading plastics into benign compounds for the environment.
A team from the U.S. Department of Natural Renewable Energy Laboratory (NREL) and the United Kingdom’s University of Portsmouth mutated the PETase gene and created a more effective enzyme. Although the altered enzyme is not yet capable of managing high levels of waste, the experiment opens many paths into genetically engineering PETase and other enzymes to increase efficiency. However, I. sakaiensis is a terrestrial bacterium and does not thrive in high salinity aquatic environments [1]. Unfortunately, the majority of plastic waste accumulates and circulates in marine environments, such as oceans, lakes, and shorelines. Thus, my research project aims to insert the gene encoding the PETase enzyme in a marine bacterium.
Transformation is the process of isolating and inserting genetic material into a foreign organism. Bacteria are especially easy to transform because they can activate genes that are not incorporated in their actual genome but are simply present within the cell. For example, bacterial DNA is shaped like a loop, but there are many smaller self-replicating DNA loops called plasmids within the microbe that can express genes [11]. My partner and I seek to take the plasmid containing the PETase gene, developed by the NREL and Portsmouth team, and transform it into the marine bacterium Vibrio fischeri. A researcher from the University of Indonesia has tried a similar experiment with a different marine bacterium, Azotobacter [9]. However, V. fischeri has been more thoroughly researched and has the additional benefit of bioluminescence. The ability to fluoresce will aid in detecting bacteria growth in response to feeding on plastics using the PETase enzyme. This marine bacterium has been standardized and is often used as a model organism, adding to its advantages [5]. Furthermore, V. fischeri is able to naturally acquire DNA in its environment, so transformation requires no special chemical or electrical procedures [6].
The plastic pollution problem must be confronted. According to the United Nation’s 2018 environmental report, humans produce 300 million tons of plastic every year. Rivers carry plastic waste into the ocean, which exponentially concentrates at high volumes. By 2050, there will be more plastic in the oceans than there are fish. Micro and macro plastics lead to many fatalities in marine life and can affect the seafood industry. Furthermore, sewer blockage and waste piles become breeding grounds for mosquitoes and other vectors that transmit malaria and other illnesses [2].
Plastic waste is especially harmful since it lasts for centuries without actually breaking down. This is why the discovery of Ideonella sakaiensis and its PETase gene provides a radiant beacon of hope for the environment's future. The research I am conducting to bring PETase into our oceans is vital to preserve our marine ecosystems and improve human health issues. Thanks to I. sakaiensis, the seafloor may one day be as pristine and magical as the aquarium’s underwater tunnels.
References
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[7] Research team engineers a better plastic-degrading enzyme [Press release]. (2018, April 16). Retrieved from https://www.nrel.gov/news/press/2018/research-team-engineers-a-better-plastic-degrading-enzyme.html
[8] Sotomayor, M. (2019, January 8). Re: Ideonella sakaiensis PETase and plastic degradation [E-mail to the author].
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