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(The Gist of Science Reporter) Engineered Enzyme Recycles Plastic Waste

[July-2020]

Engineered Enzyme Recycles Plastic Waste

According (CPCB), an enormous 25,940 tonnes of plastic waste is generated per day in India. Polyethylene Terephthalate (PET) is one of the major plastics to the 2019 estimates of Central Pollution Control Board employed in the manufacturing of bottles (packaging), fibres (textiles), films, food containers, and various thermoformed packaging and components. It is an extremely difficult plastic to degrade.
A group of French researchers from Toulouse Biotechnology Institute, CRITT Bio-Industries and Carbios, has engineered a cutinase enzyme capable of disintegrating the chains that hold the PET building blocks together. The novel modified cutinase enzyme breaks down PET waste efficiently into ethylene glycol and terephthalic acid, the latter to be used for recycling. The finding has been published in the April 9, 2020 issue of Nature.
Till now, processes that have been used to recycle the PET waste were expensive and inefficient. However, after screening and evaluating five well-known PET-digesting enzymes (PET hydrolases), the researchers engineered and tweaked ending up with an engineered LCC enzyme capable of achieving a minimum of 90% PET depolymerization in less than 10 hours, with productivity of 16.7 grams of terephthalate per litre per hour.
The group also synthesised new PET bottles using recycled terephthalic acid. The recycled PET was similar to the virgin PET synthesized using petrochemical terephthalic acid. Moreover, recycled PET bottles possessed excellent lightness values of 87.5% that is better than the minimal standard for PET bottles (greater than 85%). The researchers calculated that the cost of enzyme needed to recycle 1 ton of PET is approximately 4% of the ton-price of the virgin PET.