Solid-State Enzymatic Hydrolysis of Mixed PET/Cotton Textiles

Area of Science:

• Biotechnology
• Polymer Science
• Textile Recycling

Background:

• Polyester (PET) and cotton textile waste poses significant recycling challenges due to separation difficulties and material degradation.
• Current chemical recycling methods for PET are energy-intensive and can compromise polymer quality.
• Enzymatic recycling offers a sustainable alternative but is typically limited to high-purity PET feedstocks and requires pre-treatment.

Purpose of the Study:

• To develop a direct and selective enzymatic depolymerization method for mixed PET/cotton textiles.
• To investigate the simultaneous or sequential enzymatic breakdown of both PET and cotton components.
• To assess the yield and quality of monomers and sugars obtained from the recycling process.

Main Methods:

• Utilized a commercial cutinase from Humicola insolens for the enzymatic depolymerization of high-crystallinity PET under moist-solid conditions.
• Employed cellulase enzymes (CTec2®) for the concurrent or subsequent depolymerization of cotton fibers.
• Analyzed the yields of terephthalic acid (TPA) from PET and glucose from cotton.

Main Results:

• Achieved a direct and selective depolymerization of PET in mixed textiles to terephthalic acid (TPA) with yields up to 30±2%.
• Successfully combined PET depolymerization with cotton degradation using cellulase enzymes, yielding up to 83±4% glucose.
• Demonstrated that the combined process did not negatively impact the TPA yield, indicating process compatibility.

Conclusions:

• Enzymatic recycling of mixed PET/cotton textiles is feasible under moist-solid conditions, bypassing the need for melt-amorphization.
• This approach offers a selective and sustainable pathway for recovering valuable monomers (TPA) and sugars (glucose) from textile waste.
• The developed method provides a promising route towards a circular economy for the textile industry.