Biomass water interactions during enzymatic hydrolysis, and prospects for improved solid liquid separation of lignin residues by substrate modification

Understanding biomass-water interactions is key to developing more efficient fractionation and separation methods for lignocellulosic biomass.  This work investigates the interactions between water and biomass during enzymatic hydrolysis, and explores how these interactions may impact downstream processing. We analyzed this data with regards to assumptions about biomass behaving as a polyelectrolyte gel.   Interactions between water and biomass were measured during the enzymatic hydrolysis of pretreated wheat straw, using water retention value and low field NMR techniques.  Changes in some physical properties of the biomass during hydrolysis were measured by observing swelling in response to salts in solution, and by measuring water retention of rewetted biomass after drying, a method of approximating hornification effects.  It was observed that water retention by the biomass increased significantly during enzymatic hydrolysis, increasing steadily with cellulose saccharification .   As well, during hydrolysis, the biomass lost its ability to swell in response to changes in salt concentration and pH, and the relative difference between water retention before and after drying decreased significantly. This may perhaps be a consequence of lignin becoming the dominant species when hygroscopic carbohydrates were degraded. We give suggestions based on this data for improving downstream solid liquid separations.