Highly efficient degradation of polybutylene succinate (PBS) and polycaprolactone (PCL) by a recombinant marine fungal cutinase.

Abstract

Biodegradable plastics, such as polybutylene succinate (PBS) and polycaprolactone (PCL), pose potential ecological risks due to their slow degradation rates in natural environments. Therefore, there is an urgent need to develop efficient enzymatic degradation technologies for the end-of-life management of PBS and PCL. In this study, we identified a marine fungal cutinase, AaCut10, which exhibits significant degradation activity on PBS and PCL films under mild conditions. AaCut10 can achieve degradation rates of 26.33% for PBS and 85.67% for PCL films within 20 min at 37°C, corresponding to degradation efficiencies of 315.96  kg PBS·(mol AaCut10·h)⁻¹ and 1028.04  kg PCL·(mol AaCut10·h)⁻¹, respectively. Notably, AaCut10 showed even higher degradation efficiency on PBS and PCL emulsions, achieving degradation rates of 81.88% for PBS and 99.45% for PCL after just 1 min at room temperature. Product analysis showed that AaCut10 degrades PBS into monomers and dimers and completely degrades PCL into monomers. The optimal degradation temperature for AaCut10 was 23°C for both PBS and PCL. Even at 4°C, AaCut10 retained high degradation activity, with relative activities of 60.58% for PBS emulsion and 81.41% for PCL emulsion. Additionally, Ca²⁺, Mg²⁺, and Mn²⁺ significantly enhanced the degradation activity of AaCut10, and the enzyme remained stable in the presence of chemicals such as methanol, ethanol, and glycerol. Finally, we identified that the amino acids Leu209 and Leu216 in AaCut10 play key roles in its degradation functions toward both PBS and PCL.IMPORTANCEAlthough biodegradable plastics can be degraded, their degradation rates in natural environments are slower than expected. To address this issue, we identified a marine fungal cutinase, AaCut10, which efficiently degrades various polyesters, including PBS and PCL, into their corresponding monomers, thereby facilitating subsequent recycling and remanufacturing. Notably, AaCut10 achieves maximum degradation efficiency at ambient temperature (23°C) and retains high activity even at 4°C, meeting the energy efficiency requirements of industrial applications. Furthermore, AaCut10 exhibits high stability in the presence of chemicals, making it suitable for multiphase catalytic systems while the enhancing effects of metal ions on its activity provide tunable targets for process optimization. The catalytic properties of AaCut10 not only establish a theoretical framework for designing high-performance degrading enzymes but also offer essential support for developing eco-friendly plastic recycling systems.