Enhanced release of oxidized sugars by Lytic Polysaccharide MonoOxygenases, by the effect of synergistic action with endoglucanases

Lytic Polysaccharide MonoOxygenases (LPMOs) are considered as one of the most promising enzyme groups in the field of bioconversion of lignocellulosic substrates for the production of value added chemicals and fuels, due to their unique mechanism of action and product formation. The presence of these enzymes in combination with traditional hydrolases results in an enhanced yield of released neutral sugars from cellulosic feedstocks (Horn et al.,2012). This boosting effect on the overall conversion of cellulosic substrates by the addition of LPMOs makes these enzymes an integral part of modern cellulolytic cocktails used industrially (Cannella et al.,2012). In this study we demonstrate the synergistic action, in the release of oxidized sugars, between several endoglucanases belonging to different GH families and LPMOs with different regioselectivity (C1, C4, or both). It has been observed that the presence of endoglucanase increases the release of oxidized sugars, compared to that obtained by the action of LPMO alone. We do also show how the combined action of endoglucanases and LPMOs enhance the release of sugars, oxidatively cleaved at different carbon positions, than the oxidative sugars that are released when LPMOs are acting alone. This mode of synergy between an LPMO and a cellulase has not been reported before. This result provides new insights into how fungi degrade the plant cell wall structures by using both an oxidative activity, and by synergism with hydrolases. These findings can in the future be used for further improvement of bioconversion of lignocellulose to fuels and chemicals.