LPMO-like Activity of Bioinspired Copper Complexes: From Model Substrate to Extended Polysaccharides

Polysaccharide oxidative depolymerization is highly desirable to achieve recalcitrant biomass valorization. Inspired by recently discovered Lytic Polysaccharide Monooxygenases, mononuclear copper complexes have been prepared and studied in the literature. However, the activities were evaluated on different substrates and under various conditions. In this work we intended to establish a robust and reproducible activity assay, in aqueous solution at a pH close from neutrality and under mild conditions. We have evaluated several complexes on substrates of increasing complexity: the model substrate para-nitrophenyl-beta-D-glucopyranoside (p-NPG), cellobiose (glucose dimer), as well as on extended substrates (chitin, cellulose and bagasse from agave). The different assays were compared and proof-of-concept that bioinspired complexes can oxidatively promote polysaccharide depolymerization was obtained. Finally, we measured level of hydroxyl radicals released by the complexes under comparable experimental conditions and mechanistic pathways are discussed. The catalytic activity of several LPMO-bioinspired copper complexes was assayed on different substrates of increasing complexity (soluble to extended insoluble polysaccharides). The different assays are compared and proof-of-concept that bioinspired complexes can oxidatively promote polysaccharide depolymerization was obtained. Mechanistic pathways and catalysts stability are discussed.image