Today, plastic has become an integral part of our life. Every product we use daily, there is a certain amount of plastic that is involved, be it a mobile phone, milk container, water bottle, the list is infinite. Many are single-use plastic, for example, the disposable water bottle or the milk bottle. It finds its way to a recycling facility or a landfill after a single-use. According to the Environmental Protection Agency (EPA), in the US alone, plastic that belongs to the containers and packing category accounted for more than 14 million tonnes in 2017.
Most of the plastic that we use today, water bottles, soda bottles, milk, and juice containers, are made of a specific type of plastic commonly referred to as PET. PET stands for Polyethylene Terephthalate and is the most widely used plastic, with almost 70 million tonnes produced annually. According to the EPA, only 30% of these PET get recycled.
Predominantly recycling is done by melting a mix of various colored PET at high temperatures, resulting in a grey or black starting material. Only a few companies want to use this material. Most of them turn into carpets and other low-grade plastic fibers, which eventually ends up in landfills or gets incinerated.
Breakthrough at a French plastics company
What if there is a better way of recycling of plastic and turn them into a pristine starting material that can find its way to a plastic bottle? Researchers at Carbios, the French sustainable plastics company, have engineered an enzyme that can convert 90% of the PET plastic into its pristine starting material in a matter of hours.
The researchers at Carbios evaluated around 100,000 micro-organisms before landing on Leaf-branch compost cutinase (LLC). The researchers at Osaka University have been studying LLC since 2012. LLC slices the bond between PETs building blocks: terephthalate, and ethylene glycol and falls apart after just a few days working at 65 degrees Celsius, the temperature at which PET begins to soften but not melt.
Mutant LLC to rescue
The chief scientific officer at Carbios, Alain Marty, partnered with Isabelle Andre, an enzyme expert at the University of Toulouse to introduce mutations to LLC. After trying hundreds of mutants enzymes, the researchers isolated a mutant enzyme that is more than 10,000 times efficient at breaking the PET bond than native LLC and can operate at 72 degrees celsius. The temperature is also crucial as it is close to the temperature at which the PET becomes molten.
In a test conducted by the researchers, the enzyme was able to break down 90% of the 200 gms PET used in the analysis in a matter of 10 hours. The researchers then used the building blocks to create new PET and produce plastic bottles. The bottles were as strong as those made from virgin plastic.
Economically, the recycled PET produced by this method is expensive than virgin plastic. However, companies may be willing to pay a higher price for recycled plastic as it is more sustainable and durable
According to Alan Marty, Carbios is building a demonstration plant that is expected to recycle hundreds of tonnes of PET every year.
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