Abstract

Significance Plant cell walls are recalcitrant copolymeric structures mainly comprising polysaccharides and lignin. Enzymatic degradation of the polysaccharides is a crucial step in biorefining of biomass. Recently, it was discovered that nature employs copper-dependent redox enzymes called lytic polysaccharide monoxoygenases (LPMOs) to promote degradation of the most recalcitrant and crystalline of these polysaccharides, cellulose. By carrying out oxidative cleavage of otherwise inaccessible cellulose chains, LPMOs create access points for classical hydrolytic enzymes such as cellulases. Intriguingly, the genomes of biomass degrading microorganisms encode a plethora of LPMOs (up to over 40). To our knowledge, we demonstrate for the first time that LPMOs act on hemicelluloses. This finding dramatically widens the scope of LPMOs and oxidative processes in plant cell wall degradation and biorefining.