Enhanced Thermal and Catalytic Properties of Modified Thielavia terrestris Cutinase for Plastic Biodegradation

Cutinases provide a sustainable and eco-friendly alternative to traditional plastic treatment and recycling, thereby reducing adverse environmental effects and recovering valuable components from plastic waste. This study investigated cutinase from the thermophilic fungus Thielavia terrestris (TtC), employing site-directed mutagenesis to improve its thermal stability and catalytic efficiency. Two enhanced variants, TtC_T and TtC_QLF, were developed by incorporating residues from the more heat-stable cutinase of the fungus Humicola insolens (HiC). Among the two, TtC_T demonstrated higher activity, achieving a 1.15-fold increase in plastic degradation compared to the wild-type TtC. TtC_T also presented over 80% residual activity at 70 °C. In the polycaprolactone (PCL) film hydrolysis assays, TtC_T achieved a 56% weight reduction within 2 h and complete degradation in 24 h, highlighting its significant potential for efficient plastic breakdown.