Viscosity reduction of pretreated softwood by endoglucanases

BACKGROUND: Cost-effective processing of lignocellulosic biomass into sugar derived products, such as biofuels or biochemicals, needs to be performed at high water insoluble solid (WIS) loading. However, the difficult rheology of such materials presents significant challenges. The aim of this study was to investigate if a Cel5A endoglucanase can be used to reduce the viscosity of two types of pretreated softwood: steam pretreated Scots pine and sulfite pretreated Norway spruce. RESULTS: The viscosity of steam pretreated pine increased (by more than 60%) during the first 20min of enzymatic hydrolysis, followed by a gradual decrease. A slightly lower viscosity during prolonged hydrolysis could be obtained by replacing 25% of the protein in Cellic CTec3 with the Cel5A endoglucanase. Very different results were obtained with sulfite pretreated spruce. The viscosity of this material was rapidly reduced by either CTec3 or the Cel5A endoglucanase, without a transient initial increase in viscosity. Even very low doses of Cel5A (0.1mg protein per g glucan) decreased the viscosity of sulfite pretreated spruce 30-fold within 6h. CONCLUSION: Low endoglucanase doses can be used to reduce the viscosity of sulfite pretreated softwood, whereas the viscosity of steam pretreated softwood is less affected by endoglucanase activity

In situ measurements of oxidation–reduction potential and hydrogen peroxide concentration as tools for revealing LPMO inactivation during enzymatic saccharification of cellulose

Background: Biochemical conversion of lignocellulosic biomass to simple sugars at commercial scale is hampered by the high cost of saccharifying enzymes. Lytic polysaccharide monooxygenases (LPMOs) may hold the key to overcome economic barriers. Recent studies have shown that controlled activation of LPMOs by a continuous H2O2 supply can boost saccharification yields, while overdosing H2O2 may lead to enzyme inactivation and reduce overall sugar yields. While following LPMO action by ex situ analysis of LPMO products confirms enzyme inactivation, currently no preventive measures are available to intervene before complete inactivation. Results: Here, we carried out enzymatic saccharification of the model cellulose Avicel with an LPMO-containing enzyme preparation (Cellic CTec3) and H2O2 feed at 1 L bioreactor scale and followed the oxidation–reduction potential and H2O2 concentration in situ with corresponding electrode probes. The rate of oxidation of the reductant as well as the estimation of the amount of H2O2 consumed by LPMOs indicate that, in addition to oxidative depolymerization of cellulose, LPMOs consume H2O2 in a futile non-catalytic cycle, and that inactivation of LPMOs happens gradually and starts long before the accumulation of LPMO-generated oxidative products comes to a halt. Conclusion: Our results indicate that, in this model system, the collapse of the LPMO-catalyzed reaction may be predicted by the rate of oxidation of the reductant, the accumulation of H2O2 in the reactor or, indirectly, by a clear increase in the oxidation–reduction potential. Being able to monitor the state of the LPMO activity in situ may help maximizing the benefit of LPMO action during saccharification. Overcoming enzyme inactivation could allow improving overall saccharification yields beyond the state of the art while lowering LPMO and, potentially, cellulase loads, both of which would have beneficial consequences on process economics

3.Observation of Earthquake Ground Motions and Strains

小特集：地盤・構造物系の地震応答および破壊機構 : 千葉実験所に完成した振動台および地震応答観測システムの概