Water retention value predicts biomass recalcitrance for pretreated lignocellulosic materials across feedstocks and pretreatment methods
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Understanding the causes of lignocellulosic biomass recalcitrance is necessary for developing robust biomass conversion processes for fuels and chemicals. A key factor in biomass recalcitrance is the physical and chemical relationship between biomass and water. Water is known to be important for enzymatic hydrolysis both because it is a co-substrate for cellulose hydrolysis, but also because it acts as a swelling agent that allows enzymes access to the substrate. It has been shown that the water retention value, and water constraint as measured by spin–spin low field NMR (T2 LFNMR) techniques, correlated to biomass recalcitrance for similar lignocellulosic materials pretreated at different severities. In this work, water retention and water constraint was measured across species and pretreatment methods and compared to the enzymatic digestibility of the cellulose fraction. There is an overall positive correlation between the water retention value and glucose hydrolysis yields. Average water constraint in the samples (as represented by monocomponent T2 decay times) could not be correlated to biomass recalcitrance; however a relationship was found between the relative amount of more highly constrained water measured and hydrolysis performance. Feedstock heterogeneity and differences in sample morphology may account for the variation in the sample set. Further research is needed to develop these predictive methods, but can be applied with good accuracy on specific feedstock types or for specific pretreatment methods.
KeywordsWater retention value Biomass recalcitrance Pretreatment Water constraint Biomass-water interactions Pretreatment LFNMR
We would like to thank the following people and institutions for kindly providing materials for this study. Erik Kuhn and Dan Schell at the National Renewable Energy Laboratory, Mads Pedersen from BioGasol A/S, Henning Jørgensen from University of Copenhagen, Jack Saddler and Richard Chandra from the University of British Columbia, Demi Tristan Djajadi at the Technical University of Denmark, and Mats Galbe and Christian Roslander from Lund University. We would also like to thank Novozymes A/S for providing the enzymes for this study, and the BioValue project for funding this research.
This research was funded by the Strategic Platforms for Innovation and Research fund, which is managed by the Danish Innovation Fund, as part of the project entitled BioValue.
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Conflict of interest
The Authors declare that they have no conflicts of interest. All authors are wholly employed by the University of Copenhagen.
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