Is solvent-based dissolution and precipitation an effective substrate pretreatment for the enzymatic depolymerisation...

Area of Science:

• Materials Science
• Biotechnology
• Green Chemistry

Background:

• Poly(ethylene terephthalate) (PET) recycling faces challenges with high-crystallinity textiles.
• Enzymatic recycling of PET offers a low-energy alternative but is hindered by recalcitrant substrates.
• Current amorphisation pretreatments are energy-intensive, increasing overall process costs.

Purpose of the Study:

• To investigate dissolution-reprecipitation using green solvents as a lower-energy pretreatment for PET textiles.
• To assess the impact of gamma-valerolactone (GVL) and 2-isopropylphenol (IPP) on substrate crystallinity and enzyme activity.
• To evaluate the potential of GVL and IPP for dye removal in PET recycling.

Main Methods:

• Dissolution-reprecipitation pretreatment of PET textiles using GVL and IPP.
• Analysis of substrate crystallinity changes post-pretreatment.
• Assay of PET hydrolase LCC^ICCG activity on treated substrates.
• Thermostability and activity assays of LCC^ICCG in the presence of solvents.
• Evaluation of dye removal efficiency from polyester textiles.

Main Results:

• Minimal decrease in substrate crystallinity observed after solvent treatment.
• Enhanced activity of LCC^ICCG on all solvent-treated PET substrates.
• GVL negatively impacted LCC^ICCG thermostability; both solvents decreased enzyme activity at concentrations as low as 4%.
• Effective removal of synthetic dyes from polyester textiles by both IPP and GVL.

Conclusions:

• Dissolution-reprecipitation with GVL and IPP presents a viable, lower-energy pretreatment for enzymatic PET recycling.
• Effective dye removal by these green solvents opens new avenues for textile recycling applications.
• Careful solvent removal is crucial to mitigate enzyme inhibition and maintain enzyme performance in PET recycling processes.