Bug-Busting Spandex: Biodegrading Textile Blends for Molecular Recycling
Lead Research Organisation:
University College London
Department Name: Chemistry
Abstract
Waste textiles are a major issue worldwide and recent reports have highlighted that Britons throw away ~ 3 kg textiles each year. While some waste clothing (~10%) is resold or exported, nearly 50% ends up in landfill in the UK which is a missed recycling opportunity. The global polyester fibre market was $74 billion in 2020 and is projected to rise to $124 billion by 2027. Polyester fibre is made from processed polyethylene terephthalate (PET), including virgin fibres, and more recently recycled PET. Spandex, also known as Lycra or Elastane, is an important elastane fibre with production levels of 1 million tonnes/year. It is used in many stretchy fabrics such as activewear as a textile blend with polyesters (e.g. ratio Spandex:PET, 15:85 or less). Such blended textiles are particularly challenging to recycle into useful materials due to the complex structure, however biotechnological approaches have the potential to degrade the polymers into fragments or small molecules for recycling or upgrading into other polymers or materials.
This project aims to identify and develop enzymes for the breakdown of polyester/Spandex fabric blends and to recycle the small molecule monomers into either new polymers, for use as a feedstock for biopolymer synthesis, or as a drug precursor. This 'bug-busting' strategy for Spandex textile blends will provide routes to tackle a major problematic textile waste stream. A particular challenge of Spandex is their combination with other textiles into fabric blends, and the carbamate bonds which are hard to hydrolyse under mild conditions. While there have been significant developments recently in generating productive enzymes to break down plastic PET bottles, there has been little work carried on the breakdown of PET polyesters in textiles. There are also currently very few enzymes that cleave the carbamate bond that have been characterized.
Several strategies to obtain productive degrading enzymes for polyester/Spandex blends are proposed. Crucial to the rapid success of enzyme discovery and screening will be suitable assays and for this we will synthesise substrates for the development of chromogenic high throughput assays on an automated platform and for subsequent screening on an analytical HPLC machine. The biodegradation of polyesters will be investigated using current in-house PETases and esterases, and available PETases, together with the use of mechanoenzymatic reaction conditions and ionic liquids to enhance textile/enzyme interactions. Then the Spandex biodegradation will be explored via the identification of enzymes that can break down the carbamate bond. This will be through the development of microbial consortia/bacteria from enrichment experiments in hotbins set up two years ago, assays, DNA sequencing and enzyme identification. Also, informatics approaches and the use of databases, and metagenomic strategies including our metagenomics database. The polyester and Spandex degrading enzymes will then be combined and optimised using enzyme mutagenesis approaches and high throughput automated screening platforms. Using the best combination of enzymes, procedures will be tested to isolate the key aromatic acid and amine fragments, while the remaining soft segment components can potentially be used as a carbon feedstock for bioplastic production. A route to enhance the value of the amine fragment will also be explored using in house oxidative enzymes. Throughout the project and through links to the UCL Plastic Waste Innovation Hub we will assess the social, economic, and environmental impact of the technologies developed and gather the data for a life cycle analysis.
This project aims to identify and develop enzymes for the breakdown of polyester/Spandex fabric blends and to recycle the small molecule monomers into either new polymers, for use as a feedstock for biopolymer synthesis, or as a drug precursor. This 'bug-busting' strategy for Spandex textile blends will provide routes to tackle a major problematic textile waste stream. A particular challenge of Spandex is their combination with other textiles into fabric blends, and the carbamate bonds which are hard to hydrolyse under mild conditions. While there have been significant developments recently in generating productive enzymes to break down plastic PET bottles, there has been little work carried on the breakdown of PET polyesters in textiles. There are also currently very few enzymes that cleave the carbamate bond that have been characterized.
Several strategies to obtain productive degrading enzymes for polyester/Spandex blends are proposed. Crucial to the rapid success of enzyme discovery and screening will be suitable assays and for this we will synthesise substrates for the development of chromogenic high throughput assays on an automated platform and for subsequent screening on an analytical HPLC machine. The biodegradation of polyesters will be investigated using current in-house PETases and esterases, and available PETases, together with the use of mechanoenzymatic reaction conditions and ionic liquids to enhance textile/enzyme interactions. Then the Spandex biodegradation will be explored via the identification of enzymes that can break down the carbamate bond. This will be through the development of microbial consortia/bacteria from enrichment experiments in hotbins set up two years ago, assays, DNA sequencing and enzyme identification. Also, informatics approaches and the use of databases, and metagenomic strategies including our metagenomics database. The polyester and Spandex degrading enzymes will then be combined and optimised using enzyme mutagenesis approaches and high throughput automated screening platforms. Using the best combination of enzymes, procedures will be tested to isolate the key aromatic acid and amine fragments, while the remaining soft segment components can potentially be used as a carbon feedstock for bioplastic production. A route to enhance the value of the amine fragment will also be explored using in house oxidative enzymes. Throughout the project and through links to the UCL Plastic Waste Innovation Hub we will assess the social, economic, and environmental impact of the technologies developed and gather the data for a life cycle analysis.
Technical Summary
This project aims to identify and develop enzymes for the breakdown of polyester/Spandex fabric blends and to recycle or upgrade the fragments produced. Polyester fibre is made from processed polyethylene terephthalate (PET), while Spandex contains at least 85% of segmented polyurethane (PU), containing carbamate bonds, and 'macroglycols' soft segments. It is used in many stretchy fabrics such as activewear as a textile blend with polyesters.
Our aims are first to use polyester degrading enzymes and for these we will screen our in house esterases and PETases including a range of mutants and reported productive PETases. Using established assays these will be screened for use with polyester textiles and the application of mechanoenzymatic methods and ionic liquids. PUase discovery will be key and three approaches with be used. The first is the development of microbial consortia, and agar plate and emulsion-based screens will be used to detect PU degradation. Taxonomy of the enrichments will be examined by 16S rDNA analysis, and full genome sequences of bacteria able to degrade PUs determined. Enzyme identification will be via separation, screening and protein MS analysis. Bioinformatics methods will be used to search publicly available genomes and our metagenomic databases will be screened for enzymes by BLAST and Pfam, using the sequences of PUase degraders. For fabric blend biodegradation, the PETases and PUases will be optimised using rolling circle mutagenesis, for higher temperature and pH tolerances and greater activity for combined operation. Textile biodegradation with both PETases and PUases will then be performed. Protocols for fragment isolation with be tested and upgrading the diamine through the use of P450 enzymes. Throughout the project we will assess the social, economic, and environmental impact of the biotechnologies developed and gather the data for a life cycle analysis.
Our aims are first to use polyester degrading enzymes and for these we will screen our in house esterases and PETases including a range of mutants and reported productive PETases. Using established assays these will be screened for use with polyester textiles and the application of mechanoenzymatic methods and ionic liquids. PUase discovery will be key and three approaches with be used. The first is the development of microbial consortia, and agar plate and emulsion-based screens will be used to detect PU degradation. Taxonomy of the enrichments will be examined by 16S rDNA analysis, and full genome sequences of bacteria able to degrade PUs determined. Enzyme identification will be via separation, screening and protein MS analysis. Bioinformatics methods will be used to search publicly available genomes and our metagenomic databases will be screened for enzymes by BLAST and Pfam, using the sequences of PUase degraders. For fabric blend biodegradation, the PETases and PUases will be optimised using rolling circle mutagenesis, for higher temperature and pH tolerances and greater activity for combined operation. Textile biodegradation with both PETases and PUases will then be performed. Protocols for fragment isolation with be tested and upgrading the diamine through the use of P450 enzymes. Throughout the project we will assess the social, economic, and environmental impact of the biotechnologies developed and gather the data for a life cycle analysis.
