Overview
We decided to engineer Chlamydomonas reinhardtii with an enhanced enzyme system to upcycle plastic waste: This system will depolymerize Polyethylene terephthalate (PET) into reusable building blocks in order to upcycle PET into a high-end product, vanillin. Our goal is to address both the poor management of post-consumer plastic waste and the pressing need to apply circular economic solutions to those fossil fuel products.
The Problem
Imagine a world where our plastic waste transforms into valuable resources through synthetic biology. This vision is not only fascinating but essential, in a world where plastic production - and subsequently, though not to a proportional degree, waste - has more than doubled over the past two decades. Polyethylene terephthalate (PET), the most widely produced and common polymer worldwide, is most often found in bottles and packaging, contributing significantly to ocean and landfill pollution. Currently, about 70% of global plastics become waste. Only around 41% of post-consumer plastic waste is recovered through recycling or incineration, while 40% is disposed of in landfills and 19% makes its way into oceans or onto coastlines. At present, the accumulation of PET waste is steadily increasing and poses a growing threat to ecosystems worldwide. It is estimated that microorganisms in the environment take hundreds of years to fully degrade PET plastics. Developing microorganisms capable of degrading PET into vanillic acid holds promise as it transforms plastic waste into a valuable molecule used across various industrial sectors. This approach provides a sustainable pathway for utilizing plastic waste and supports a circular economy.
We all know how recycling is an important part of managing environmental pollution levels, but right now less than 20% of plastic waste goes through this process. We thus realized implementing upcycling as a key aspect of the project, so as not to simply degrade a compound but create a new high-value one, would enable us to organically implement it to a large-scale bioproduction. Such an approach would allow not only to degrade PET, but to valorise it. This led us to the search for a compound that would meet two requirements: to be feasibly synthesized through enzymatic processes, and be a highly sought out primary compound. We found that vanillin demands far exceed the offer, and got to work.
Our Solution
Recently, Japanese researchers identified the bacterium Ideonella sakaiensis, which is capable of producing the enzymes necessary to break down PET plastic into its two main components: TPA and EG. This transformation is made possible by the expression of two specific enzymes, named PETase and MHETase. The reactions of these enzymes are illustrated below.
PET
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Section 2
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Section 3
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Section 4
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