Challenges in Aqueous-Phase Biomass Hydrolysis
In the cellulolysis processes or aqueous phase process, the most challenging step is the depolymerization of cellulose and hemicel — lulose in the biomass to a fermentable sugar solution, or the saccharification. The resistance of lignocellulosic biomass to the hydrolysis by enzymes or acid is one of the most formidable barriers for the production of cellulosic ethanol. This resistance or non-susceptible nature of the lignocellulosic structures, which does not allow other molecules to easily penetrate or interact with the molecular structure, is known as the recalcitrance of cellulose. Insolubility of cellulose and lignocellulosic biomass in most of the common solvents is a direct consequence of recalcitrance property as well. Recalcitrance character is related to the structure of cellulose and lignocellulosic biomass. Hence, a sound understanding of the molecular architecture of cellulose and lignocellulosic biomass is an extremely important aspect of cellulosic biomass science and a good launching point for biomass pretreatment and saccharification research.