High-efficiency depolymerization/degradation of polyethylene terephthalate plastic by a whole-cell biocatalyst

Area of Science:

• Biotechnology and Environmental Science
• Enzyme Engineering for Plastic Degradation

Background:

• Polyethylene terephthalate (PET) is a widely used plastic but a major source of persistent pollution.
• Existing PET hydrolases, like ICCG, show high activity but require purification, limiting industrial application.
• There is a growing need for efficient and environmentally friendly PET biodegradation methods.

Purpose of the Study:

• To develop a novel mutant of the leaf-branch compost cutinase ICCG with improved whole-cell biocatalytic activity for PET degradation.
• To enhance the industrial utility of PET hydrolases by enabling efficient degradation using whole microbial cells.

Main Methods:

• Employed rational design and combinatorial mutagenesis to create new ICCG enzyme variants.
• Developed the RITK mutant (D53R/R143I/D193T/E208K) from the ICCG enzyme.
• Assessed whole-cell biocatalytic activity and thermostability of the RITK mutant compared to ICCG.

Main Results:

• The RITK mutant demonstrated an 8.33-fold increase in whole-cell biocatalytic activity compared to ICCG.
• RITK also exhibited improved thermostability.
• Purified RITK showed a 12.75-fold increase in PET depolymerization at 85°C for 3 hours compared to ICCG.

Conclusions:

• The RITK mutant significantly enhances whole-cell PET biodegradation capabilities.
• This development greatly improves the industrial feasibility of using enzymes for PET recycling.
• The findings contribute to advancing sustainable plastic waste management solutions.