Engineering a robust IsPETase for energy-efficient PET depolymerization in natural seawater at ambient temperatures

Area of Science:

• Biotechnology
• Environmental Science
• Materials Science

Background:

• Polyethylene terephthalate (PET) recycling is crucial due to its widespread use.
• Enzymatic depolymerization in seawater is an underexplored, energy-efficient recycling strategy.
• Limited research exists on PET hydrolase performance in saline environments.

Purpose of the Study:

• To screen and engineer PET hydrolases for efficient depolymerization in seawater.
• To develop a robust enzymatic platform for plastic bioconversion in marine environments.
• To assess the potential of seawater-based recycling for polyethylene terephthalate.

Main Methods:

• Screening of eight enzymes in artificial seawater at 30°C.
• Semi-rational engineering of the most active enzyme, IsPETase, focusing on rigidifying flexible sites.
• Characterization of the engineered variant (M8) for thermostability, activity, and expression yield.

Main Results:

• Engineered variant M8 showed enhanced thermostability (+27.3°C), activity (1.14-fold), and expression yield (14.3-fold).
• M8 depolymerization efficiency surpassed benchmark enzymes DuraPETase (32.2-fold) and LCC-ICCG (10.4-fold).
• M8 efficiently depolymerized 15% PET powder in natural seawater at 37°C, producing monomers at 15.4 mM/day.

Conclusions:

• The engineered M8 enzyme provides an efficient platform for PET depolymerization in saline conditions.
• This study demonstrates the feasibility of seawater-based bioconversion processes for plastic recycling.
• The findings pave the way for integrated, environmentally friendly plastic waste management solutions.