Novel approach for untreated household PET waste depolymerization: recombinant extracellular thermostable hydrolases

Area of Science:

• Biotechnology
• Environmental Science
• Polymer Science

Background:

• Plastic waste, particularly polyethylene terephthalate (PET), poses a significant global environmental challenge due to its persistence.
• Efficient and sustainable methods for PET waste degradation are crucial for mitigating environmental pollution.

Purpose of the Study:

• To evaluate the enzymatic depolymerization of non-pretreated household PET waste using two plastic-degrading esterases, LCC^ICCG and IsPETase^W159H/F229Y.
• To leverage the advantages of extracellular expression in a Pichia pastoris system for enhanced enzyme stability and recovery.
• To assess the potential of these enzymes for large-scale, environmentally sustainable PET waste management.

Main Methods:

• Extracellular expression of LCC^ICCG and IsPETase^W159H/F229Y in Pichia pastoris.
• Determination of enzyme activity levels and stability at various temperatures and time points.
• Assay of PET depolymerization efficiency using non-pretreated household PET waste.

Main Results:

• Expression in Pichia pastoris yielded high esterase activity levels (86.3 IU/mg for LCC^ICCG and 16.4 IU/mg for IsPETase^W159H/F229Y) with retained activity for over 30 days at 4 and 25 °C.
• LCC^ICCG demonstrated high PET degradation efficiency (87.6 g_PET h^-1 g_enzyme^-1) and outstanding space-time yield (183.1 mM_TAeq h^-1 mg_enzyme^-1).
• IsPETase^W159H/F229Y showed a tenfold increase in depolymerization efficiency compared to previous reports (1.71 g_PET h^-1 g_enzyme^-1).

Conclusions:

• Extracellular expression in Pichia pastoris provides a robust platform for producing stable and active PET-degrading enzymes.
• LCC^ICCG is a highly promising biocatalyst for industrial applications, particularly in high-temperature PET waste treatment.
• These findings support the development of cost-effective and sustainable PET waste management strategies by reducing the need for pre-treatments.