Breaking Down Plastic Waste

Recycling plastics presents a challenge: when they are melted and reshaped, the new material often does not possess the same characteristics as virgin plastic. This is why creating new plastic is frequently more straightforward than recycling existing materials.

This raises an important question: can we find alternative uses for plastic other than simply manufacturing more of it? One innovative approach involves hydrolyzing plastic polymers, which are large molecules formed by repeating smaller units, back into these smaller components. The premise is that these smaller molecules could be more useful than the original polymer.

For instance, polyethylene terephthalate (PET), commonly used in beverage containers, can be broken down into terephthalic acid and ethylene glycol. These smaller compounds might be easier to convert into more valuable materials. Until recently, a significant hurdle to this method was the absence of an effective enzyme capable of degrading PET efficiently. Despite numerous attempts, scientists had limited success with various enzymes.

However, a breakthrough occurred in 2020 when researchers developed 209 different variations of an enzyme known as Leaf-branch Compost Cutinase, initially derived from the bacteria Ideonella sakaiensis. This enzyme had previously only managed to convert 31% of PET into smaller subunits.

The researchers meticulously tested all 209 variations to evaluate their effectiveness in breaking down PET from bottles. While most of the modified enzymes fell short, one variant achieved an impressive 90% efficiency in converting PET into its constituent parts. This marked a significant advancement, demonstrating that when these smaller subunits were used to recreate PET, they exhibited the same properties as new PET, thereby establishing a circular plastic economy.

Making Plastic Edible

While recycling PET into second-hand plastic is a positive step, another group of scientists aspired to achieve even more. They sought to upcycle the two subunits—terephthalic acid and ethylene glycol—into something more valuable rather than keeping them trapped in a perpetual plastic cycle.

Interestingly, the researchers noted that terephthalic acid shares structural similarities with vanillin, the primary flavor compound in vanilla. They devised a plan estimating that it would take only five steps to transform terephthalic acid into vanillin.

Although the steps were theoretically viable, some required specific enzymes found in various organisms. To overcome this obstacle, the team engineered a microorganism equipped with all the necessary enzymes for upcycling. They modified Escherichia coli (commonly known as E. coli) by inserting three plasmids to enable it to synthesize vanillin from terephthalic acid.

Afterward, they used terephthalic acid sourced from plastic bottles as food for the engineered bacteria and monitored the results. Remarkably, after just ten hours, 79% of the terephthalic acid had been converted into vanillin. This was a significant achievement, proving that flavor compounds could indeed be synthesized from plastics by combining the hydrolysis of PET with the metabolic activity of the genetically modified E. coli.

Would You Consume Food Derived from Plastic?

Even though the vanillin produced from plastic is chemically identical to the artificial vanilla flavoring available in stores—and even to that found in actual vanilla beans—it's likely that many would remain skeptical. It's understandable; the notion of eating food made from recycled plastic bottles can be unsettling, though it certainly piques curiosity.

Furthermore, the genetic modifications made to the enzyme and bacteria involved in this process may raise eyebrows. On the flip side, this innovative approach addresses the enormous problem of plastic pollution we have created. Additionally, using upcycled vanillin could significantly reduce costs for consumers, especially when compared to the high price of natural vanilla flavor derived from the notoriously difficult vanilla orchid.

Not to mention the labor-intensive process of harvesting vanilla beans—each flower must be hand-pollinated individually. If upcycled food does not gain mainstream acceptance, there are still alternative applications for the vanillin produced. It could be used in non-food items such as perfumes and fragrances, as vanilla scents are prevalent in various personal care products.

The future remains uncertain, as the upcycling process has only been tested on a small scale and needs substantial scaling up to make a real impact on our plastic problem. Nevertheless, this study has led me to consider the idea of converting plastic waste into food ingredients—a truly innovative and creative solution that may initially seem outlandish.

This video explores the world's first ice cream made from plastic waste, posing the question: would you dare to taste it?

In this video, an artist discusses the creation of the world's first ice cream made from plastic, and the public's reaction to this unusual food source.