LPMO-mediated oxidation increases cellulose wettability, surface water retention and hydrolysis yield at high dry matter

The cellulose-water interface is a dynamic environment mostly dominated by interactions between water molecules and hydroxyl groups protruding from the top layer of the polysaccharide chains. This interface has attracted increasing interest within the context of hydrolysis with glycosyl hydrolases, and studies on the role of tightly bound and free water has emerged. At the molecular level, cellulose-bound water has been considered important to allow enzymatic hydrolysis at industrial relevant conditions, i.e. at high dry matter (HDM) contents. In the presence of lytic polysaccharide monooxygenase enzymes, the hydrolysis can with effective yields be run at well beyond the dry matter limit previously set by the 1st generation of enzyme preparations lacking LPMOs. The oxidative cleavage of the cellulose chain performed by LPMOs allow a higher level of synergism with GH in terms of accessibility of the cellulose surface. In this work, we studied how cellulose oxidation by LPMO increases the cellulose-water interaction and the impact of this on cellulose saccharification. Low-field NMR, water constraint and enzyme kinetics at high dry matter contents were used to characterize the cellulose-water interaction and its implications in enzymatic cellulose hydrolysis.