Characterization of novel hydrophobic lytic polysaccharide monooxygenases and their interaction with plastic polymers

Abstract

The global issue of plastic pollution poses a formidable environmental concern, contributing to extensive ecological harm across terrestrial and marine environments. The resilience of plastics, attributed to their robust chemical composition, cause difficulty in terms of degradation and recycling. Lytic polysaccharide monooxygenases (LPMOs) are mono-copper enzymes capable of degrading recalcitrant polysaccharides such as chitin and cellulose through oxidative mechanisms. Due to the similarities in chemical structure between recalcitrant polysaccharides and plastic polymers, the powerful chemistry catalyzed by LPMOs emerge as potential biocatalysts for the degradation of plastics.

This master’s thesis was aimed at characterizing novel bacterial LPMOs from the AA10 family selected for hydrophobic substrate-binding surfaces. The approach was to explore whether this property could allow enzymatic binding and oxidizing activity towards various plastic polymers, in addition to chitin. The work presented in this thesis shows that three LPMOs with significantly hydrophobic substrate-binding surfaces exhibited enzymatic activity towards chitin, assessed via MALDI-ToF mass spectrometry and high-performance liquid chromatography (HPLC). Furthermore, these LPMOs, named ChaLPMO10D, SglLPMO10B, and the catalytic domain of PalLPMO10D exhibited a degree of binding towards various plastic substrates, including polyethylene, polypropylene, and polyethylene terephthalate. This finding is significant as it suggests the potential for these naturally chitin-active enzymes to interact with synthetic materials. Such interactions, could be harnessed and enhanced through bioengineering techniques to develop LPMOs capable of degrading or modifying plastics, thereby contributing to innovative solutions in recycling and waste management.