Optimized whole-cell depolymerization of polyethylene terephthalate to monomers using engineered Clostridium...

Area of Science:

• Biotechnology
• Environmental Science
• Microbial Engineering

Background:

• Polyethylene terephthalate (PET) is a major environmental pollutant due to its fossil fuel origin and poor waste management.
• Enzyme-based recycling of PET is commercialized, but whole-cell approaches are nascent.
• Developing efficient whole-cell biocatalysts is crucial for sustainable PET waste management.

Purpose of the Study:

• To engineer a stable and efficient whole-cell biocatalyst for PET depolymerization.
• To optimize reaction conditions for enhanced PET conversion using whole-cell systems.
• To demonstrate the viability of whole-cell biocatalysis for industrial PET recycling.

Main Methods:

• Engineered a Clostridium thermocellum whole-cell catalyst by integrating beneficial leaf-branch compost cutinase (LCC) variants into its chromosome for stable expression.
• Implemented a pH-controlled bioreactor to maintain optimal conditions and mitigate pH drops during depolymerization.
• Utilized pretreated waste PET as substrate for the whole-cell biocatalyst.

Main Results:

• Achieved 96.7% conversion of pretreated waste PET into terephthalic acid (TPA).
• Demonstrated stable enzyme expression and cell growth under optimized conditions.
• Completed the depolymerization process within 10 days in a 1-L reactor.

Conclusions:

• Whole-cell biocatalysts, when optimized, offer a promising and efficient method for PET recycling.
• The engineered Clostridium thermocellum system represents a significant advancement in bio-based PET waste solutions.
• This approach highlights the potential for sustainable plastic waste management through microbial biotechnology.