Recent advances in understanding the role of cellulose accessibility in enzymatic hydrolysis of lignocellulosic substrates

Cellulose accessibility has been proposed as a key factor in the efficient bio-conversion of lignocellulosic biomass to fermentable sugars. Factors affecting cellulose accessibility can be divided into direct factors that refer to accessible surface area of cellulose, and indirect factors referring to chemical composition such as lignin/hemicellulose content, and biomass structure-relevant factors (i.e. particle size, porosity). An overview of the current pretreatment technologies special focus on the major mode of action to increase cellulose accessibility as well as multiple techniques that could be used to assess the cellulose accessibility are presented in this review. The appropriate determination of cellulose accessibility before and after pretreatment can assist to understand the effectiveness of a particular pretreatment in overcoming lignocellulosic recalcitrance to improve substrate enzymatic digestibility.