Ultraviolet Ozone Pretreatment Enhances Selective PETase Biodegradation of Textiles Compared to Sunlight and Alkali Treatments

The rapid growth of the fashion industry has led to increasing textile waste, exacerbating environmental pollution and climate change. To support sustainability and circular economy goals, this study investigates the enzymatic degradation of cotton/polyethylene terephthalate (PET) mixed textiles using PETase, comparing wild-type and mutant (MUT S238F/W159H) variants. To improve enzyme accessibility, three pretreatment strategies are evaluated: alkali treatment, UV-ozone (UVO) exposure, and natural sunlight weathering. The effects are assessed by measuring textile weight loss, surface morphology (scanning electron microscopy), Fourier transform infrared spectroscopy, and yields of terephthalic acid (TPA) and mono-(2-hydroxyethyl) terephthalic acid. Alkali treatment produces the highest weight loss, while UVO pretreatment moderately degrades textiles and significantly enhances enzymatic TPA production. In contrast, prolonged sunlight exposure has negligible effects. ¹H NMR analysis of supernatants confirms the formation of oxidized PET products following UVO exposure, indicating surface chemical modifications that increase enzymatic susceptibility. The results reveal differential effects on PET and cotton fibers, highlighting UVO as a promising, selective pretreatment for mixed textile waste. This study demonstrates the potential of combining photochemical oxidation and enzymatic processes for targeted PET degradation, contributing to more efficient textile recycling strategies.