Research led by Muhammad Alyan

Syed Saim Ali, Ansa Ismail, Saman Shahid

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The Plastic Problem‍

Plastic pollution has become one of the most serious pressing environmental issues in the world nowadays, with millions of tons of plastic waste being added to landfills, oceans, and ecosystems every year. Plastic is for the convenience of using it and is very versatile; however, since it is durable, it can stay in the environment from hundreds to thousands of years before breaking down into microplastics, which then leak into the water, soil, and hence enters the food chain. Although global production of plastic keeps on increasing, doubling up by 2040, waste management initiatives have not been able to do much for them, leaving a wake of devastation behind and threatening wildlife and human health with each passing day. With recycling systems filled to capacity and increasing consumption, a new approach is becoming very critical when dealing with this complex and mounting challenge.

How The Plastic Eating Bacteria Was Discovered

In 2001, a team of Japanese scientists led by Kohei Oda, a microbiologist at the Kyoto Institute of Technology, made a remarkable discovery at a rubbish dump in Sakai, Japan. While searching for microorganisms that could soften synthetic fabrics like polyester, Oda's team stumbled upon a slimy bacterial film breaking down plastic waste. These bacteria not only attacked the surface of plastic but appeared to fully decompose it, converting it into basic nutrients. Despite the potential significance of the find, it initially garnered little attention. At the time, plastic pollution wasn’t widely recognized as a pressing issue, and their early research on the bacteria wasn’t published. Years later, as the plastic waste crisis became undeniable, Oda and his student Kazumi Hiraga continued their work. In March 2016, they published their findings in the journal Science, introducing the world to the bacterium they named Ideonella sakaiensis, after the city where it was discovered. During their research, scientists had collected plastic bottles from a recycling facility and identified the bacteria breaking down the plastic. While bacteria typically consume dead organic material, I. sakaiensis had developed the ability to degrade a specific type of plastic called polyethylene terephthalate (PET), commonly used in clothing and packaging. The study revealed that I. sakaiensis produces a unique enzyme called PETase, which hydrolyses PET into mono(2-hydroxyethyl) terephthalic acid (MHET). This compound is further broken down by another enzyme, MHETase, releasing basic nutrients that the bacteria absorb as a source of energy. This combination of PETase and MHETase makes I. sakaiensis more efficient at breaking down PET than any other known enzyme. Since the bacterium relies on external carbon sources for energy instead of producing its own throughphotosynthesis, it is classified as a heterotrophic organism. The research demonstrated that PETase enables I. sakaiensis to metabolize plastic, suggesting its potential as a solution for managing plastic waste.

However, challenges remain. I. sakaiensis thrives within a pH range of 7.0–7.5 and a temperature range of 30–37°C, although it can grow outside these conditions. In the study, cultures were grown in a bioreactor optimized at 30°C. These bacteria were cultured and modified to improve performance rather than being studied in their natural state. A significant concern is the potential environmental risk if these modified bacteria were to escape into the wild. If they began breaking down plastics outside controlled environments, packaging designed for durability could be compromised. This could prompt the plastic industry to develop plastics resistant to such bacterial activity, potentially undermining this recycling solution. Although I. sakaiensis has been studied extensively for its unique MHETase enzyme, it has limitations, including sensitivity to changes in temperature and pH, whereas other organisms may be more resilient. Additionally, PETase is effective only against PET plastics, leaving six other types of plastic for which no enzyme-based solutions currently exist. As scientists work to improve the efficiency of I. sakaiensis, some are taking innovative approaches. For instance, researchers at Reed College in Portland, Oregon, are exploring the use of multiple bacterial species to degrade PET more effectively. Similarly, genetic scientists have experimented with engineering bacteria like E. coli to act as "PETase factories," producing large amounts of the enzyme. While the discovery of I. sakaiensis provides hope in tackling the plastic waste crisis, it is clear that widespread commercial application is still years away

‍How They Eat Plastic

PET plastic consists of repeating units of the chemical formula C10H8O4. This type of molecule is called a monomer. Monomers can chemically bond with one another to create long chains known as polymers. Different types of plastic are made by using different monomers to form these polymers. The bonds between monomers in polymers are exceptionally strong, giving plastic its toughness and durability. You can observe this strength firsthand by trying to tear a plastic water bottle with your bare hands—it’s nearly impossible! These strong bonds are also why plastics persist in the environment for extended periods. Natural processes can usually only break plastic into smaller fragments but cannot fully separate the polymer chains. What makes Ideonella sakaiensis unique is its ability to break the bonds between monomers in plastic. It achieves this through the use of enzymes, which are molecules that living organisms rely on to speed up chemical reactions essential for life processes. In bacteria, enzymes play an important role in digestion. Digestive enzymes break down large molecules into smaller ones that bacteria can absorb. The bacteria use what they need from these molecules and excrete the rest. Ideonella sakaiensis produces an enzyme known as PETase, which is capable of breaking the strong bonds in PET polymers. This processreleases monomers, which the bacteria then absorb and utilize as a source of energy. This mechanism is similar to how humans digest food. Upon studying this bacterium, scientists discovered that it produces two key enzymes for digestion: PETase and another enzyme involved in breaking down the resulting monomers. When these enzymes interact with PET plastic, they break the long molecular chains into smaller monomers, specifically terephthalic acid and ethylene glycol. These monomers are further broken down to release energy, fuelling the bacteria’s growth. Following the discovery of this plastic-degrading bacteria, genetic scientists began exploring ways to enhance its efficiency. One approach has been to genetically modify other bacteria, such as E. coli, to improve enzyme production. These engineered bacteria act as "PETase factories," producing larger amounts of the enzyme. While this breakthrough brings hope in addressing the global plastic waste crisis, scientists emphasize that widespread commercial application is still years away. Moreover, PETase is effective only against PET plastic, but there are six other major types of plastic for which enzyme-based solutions remain undeveloped.

How This Can Benefit The World

As the name suggests, Plastic-eating bacteria’s biggest benefit to the world is its sustainable approach of plastic waste reduction that is accumulated in the oceans and on land. These bacteria can breakdown the plastic waste in the oceans that present a threat to marine life, and they can breakdown plastic waste in landfill sites to free up more space for other waste. Plastic-eating Bacteria breaks down the plastic into simpler molecules allowing for the byproducts of this process to be used to produce other materials, for example, PET (Polyethylene terephthalate) decomposition by the Plastic-eating Bacteria Ideonella sakaiensis produces terephthalic acid which can be reused for more PET production. Alongside this, this method of waste management is more energy efficient than other methods such as incineration. It occurs in more regular conditions and has significantly less carbon emissions compared to incineration. As the problem of plastic waste is present in many countries including third world countries without the necessary infrastructure for plastic waste management, the introduction of a simpler and more accessible method to manage waste.

Drawbacks/Problems

Plastic-eating bacteria have great potential, but there are several challenges and risks to consider. They are not fast enough to handle the massive amount of plastic waste, often taking weeks or months to break it down. For example, Ideonella sakaiensis can break down PET in lab conditions, but scaling this process to handle millions of tons of waste is difficult. Most bacteria only work on specific types of plastics, like PET or polyurethane, leaving others, such as polyethylene, polypropylene, and PVC,untouched. Mixed or layered plastics are even harder to break down. Releasing these bacteria into nature could upset local ecosystems, harming other microbes or disrupting nutrient cycles. They also don’t always fully break down plastics; the process can leave behind microplastics or harmful byproducts like toxic chemicals. These bacteria need specific conditions to work well, like certain temperatures or oxygen levels, which are hard to maintain outside controlled environments. Scaling up their use is expensive and requires special equipment, making it difficult for poorer regions to adapt. In natural settings, native bacteria might outcompete them, or the introduced bacteria might cause new ecological problems. Genetically modified bacteria, which are often needed to improve efficiency, bring concerns about spreading uncontrollably in the environment. There’s also a risk that people might rely too much on these bacteria and continue producing plastic instead of finding sustainable alternatives. Lastly, if not carefully managed, these bacteria could damage things like plastic pipes or insulation. These challenges show the need for careful research and regulation to use them safely and effectively.

Conclusion

A Japanese scientific group, led by Kohei Oda, found a bacterium that could dissolve plastic waste in 2001. This bacterium was found in a waste dump in Sakai, Japan, while the team had been looking for microorganisms that could ‘eat’ plastic material. At first, the breakthrough went unnoticed because environmental waste wasn’t a major issue then. However, in the year 2016, Oda, in conjunction with his pupil Kazumi Hiraga, published a paper that woke the entire world up, showing that I. sakaiensis was able to degrade polyethylene terephthalate, which is a plastic majorly used in the packaging of a wide variety of products as well as in clothing. The bacterium metabolizes strong plastics PET into weaker ones through the two enzymes, i.e. PETase and MHETase. While this advancement provides potential solutions to this issue and confirms the expectation of treating such human waste, certain problems remain. I. sakaiensis bacterial heater has a pH, temperature range, and plastic type efficiency among other problems. In any case I. sakaiensis is active only against the PET plastics, considering there are more than a few types of plastic. It also raises environmental concerns because it is possible that the genetically modified bacterium could be released into the environment. But advances are in progress like genetically modifying E. coli to produce more PETase to try and increase the efficiency but commercial use of the technology is still several years. Such encouraging advances, however, are balanced by the difficult incontinence of the plastic waste crisis. The bacteria that consume plastics, especially Ideonella sakaiensis, are a viable and ecological approach to address the increasing plastic trash especially in the oceans andlandfills. Instead of being considered a threat, waste products such as terephthalic acid, that can be synthesized by the bacteria consuming plastics, can be transformed into useful substances needed to assist the formation of more PET by converting plastic to simple building blocks. Furthermore, compared to incineration– which is quite laborious, and cost accurate– disintegration via these organisms biologically is rather cost active, defixed carbon emissions while boosting operational efficiency. This is especially crucial in principles of areas that do not have adequate waste disposal amenities. However, there exist several significant obstacles to fulfill their potential. One, they are slow, often requiring weeks and even a month to completely break down selected plastics only of their types and many remain unscathed. Moreover, the use of these bacteria will have dire repercussions for the environment where they are liberated, microplastics will be created, ecosystems ruined, or damaging waste products released. Moreover, the costs of increasing their use are high and it is impossible to maintain the optimum conditions to enhance their activity outside special laboratories. Lastly, the use of these bacteria poses threats in form of genetic alterations and disturbances of the ecological balance. As such, while plastic-eating bacteria appear to have great potential, their use needs to be carefully