Efficient Recycling of PET-PE Multilayer Packaging Materials Based on Enzymatic Depolymerization of PET

Area of Science:

• Biotechnology
• Polymer Science
• Sustainable Chemistry

Background:

• Mechanical recycling faces challenges with mixed plastic waste, particularly multilayer materials.
• A sustainable, circular economy necessitates improved plastic recycling technologies for high-quality outputs.

Purpose of the Study:

• To investigate the enzymatic hydrolysis of PET-PE multilayer packaging waste.
• To assess the feasibility of using polyester hydrolases for depolymerization without pretreatment.

Main Methods:

• Production of polyester hydrolases using recombinant Pichia pastoris yeast.
• Enzymatic depolymerization of PET-PE multilayer trays at laboratory and scaled-up (4.5 kg) levels.
• Isolation and repolymerization of terephthalic acid into rPET; alkaline cleaning and reprocessing of PE into rPE films.

Main Results:

• High PET depolymerization yields (≥94% at lab scale, ≥95% at scale-up) and terephthalic acid recovery (≥80%) were achieved.
• Recycled PET (rPET) was successfully repolymerized.
• Recovered PE was reprocessed into films with properties comparable to virgin low-density PE.

Conclusions:

• Enzymatic hydrolysis is a viable method for recycling PET-PE multilayer waste.
• This approach offers a sustainable alternative to conventional recycling, with broad potential for mixed polyester waste.