Efficient Bioprocess for Mixed PET Waste Depolymerization Using Crude Cutinase

Area of Science:

• Biotechnology
• Environmental Science
• Biochemistry

Background:

• Several plastic-degrading enzymes capable of depolymerizing polyethylene terephthalate (PET) have been identified.
• Efficient depolymerization of mixed PET waste remains a challenge for industrial applications.

Purpose of the Study:

• To develop and optimize a bioprocess for the depolymerization of mixed PET waste using crude, extracellularly expressed enzymes.
• To evaluate the efficiency of different enzymes (FastPETase, LCC, LCC^ICCG) in breaking down various forms of PET waste.

Main Methods:

• Screening of FastPETase, LCC, and LCC^ICCG enzymes for PET depolymerization of amorphous PET powder and films.
• Optimization of enzyme conditions and cultivation of LCC^ICCG-producing E. coli in a bioreactor.
• Application of crude LCC^ICCG supernatant for depolymerizing mixed PET waste in a bioreactor.

Main Results:

• LCC^ICCG achieved up to 70% depolymerization of PET waste under optimized conditions without pH control.
• Extracellular LCC^ICCG production in E. coli yielded 119 ± 5 mg L^-1 protein with a specific activity of 1232 ± 18 U mg^-1.
• A bioprocess using crude LCC^ICCG achieved 78% and 50% yield for mixed PET waste (MW1 and MW2) in 60 hours at 62 °C.

Conclusions:

• A cost-effective and efficient bioprocess for mixed PET waste depolymerization was successfully developed using crude LCC^ICCG.
• The developed strategy shows significant potential for large-scale plastic waste treatment and recycling.
• This approach offers an accessible method for PET depolymerization, reducing reliance on purified enzymes.