Summary
In the last two decades, due to the fast fashion phenomenon, the average global annual consumption of textiles has doubled from 7 to 13 kg per person and reached to the threshold of 100 million tonnes of textiles consumption, implying an increased amount of textiles discarded as waste. More than two-thirds of this waste ends up in landfills, and only 15% is recycled. Among synthetic fabrics, polyester (polyethylene terephthalate, PET), is the most widely used in the textile industry, accounting for 50% of the world market for synthetic fibers. Polyester fiber recycling is not carried out on a large scale because there are still no economically viable technologies for its recovery without keeping their original properties.
The overall objective of CREPÉ is to develop an enzymatic technology for PET fiber recycling using a free and immobilized cutinase (LCCICCG) with high thermostability. To achieve this goal, three tasks will be considered.
In task 1, cutinase will be cloned and expressed in bacteria to obtain the free enzyme. In addition, the muNS-Mi protein-based technology platform will be used to express and immobilize the enzyme onto nanospheres (NS). The enzymes will be purified and characterized in terms of kinetics, pH, stability and reusability. Finally, a sufficient amount of enzymes will be produced at bioreactor scale for use in the subsequent tasks of the project.
Task 2 will test the enzymes with different PET fibers (amorphous/crystalline, presence of dyes, additives, etc.) and optimize the reaction conditions with free and NS-immobilized enzyme. The possibility of depolymerizing PET/cotton blends will also be studied by combining cutinase with commercial cellulases.
In task 3, two different reactors will be operated: an enzymatic membrane reactor that recovers free cutinase using an ultrafiltration membrane, and a reactor with immobilized enzyme on NS, where particles are recovered by centrifugation.
CREPÉ presents a multidisciplinary and interdisciplinary research proposal that encompasses the areas of Molecular Biology and Chemical Engineering. Both disciplines are necessary to address the complex and great challenge of developing a technology for the enzymatic recycling of PET waste. The scientific-technical impact of the project is high, as a simple and cost-effective process for the expression of enzymes of great interest in the PET value chain will be developed. Finally, finding an efficient and environmentally friendly strategy for environmentally friendly PET recycling will have enormous environmental and social benefits. Increasing the amount of recyclable PET would reduce the waste that ends up in landfills and those incinerated, decreasing the spread of toxic and volatile wastes that are hazardous to the environment.
Key words: PET, fibres, nanospheres, recycling, enzymes, technology, bioeconomy, bioreactor, cutinases