Biomass recalcitrance. Part I: the chemical compositions and physical structures affecting the enzymatic hydrolysis of lignocellulose

TLDR

Lignocellulosic biomass resists biodegradation because its rigid, compact cell wall structure and chemical composition form a protective network that limits cellulose accessibility. This review summarizes how chemical composition and physical structure affect enzymatic digestibility of lignocellulose and proposes future research on microscale and nanoscale mechanisms. The authors analyze the impact of lignin, hemicellulose, acetyl groups, pore size, particle size, surface area, crystallinity, and polymerization on enzymatic hydrolysis. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd.

Abstract

Abstract Lignocellulosic biomass is recalcitrant to biodegradation due to the rigid and compact structure of plant cell wall. The recalcitrance of biomass is mainly constructed by its chemical compositions that build a spatial network as a protective bulwark. Generally, the factors affecting the accessibility of biomass cellulose can be divided into direct and indirect factors. The direct factors refer to the accessible surface area, and the indirect factors include biomass structure‐relevant factors (pore size and volume, particle size, and specific surface area), chemical compositions (lignin, hemicelluloses, and acetyl group), and cellulose structure‐relevant factors (cellulose crystallinity and degree of polymerization). Pre‐treatment is actually the process to alter indirect factors and improve direct factors thus enhancing the accessibility of cellulose. In this review, we summarize the effects of chemical compositions and physical structures on the enzymatic digestibility of lignocellulosic biomass. We suggest that future work should be focused on but not limited to the molecular mechanisms of biomass recalcitrance by investigating the microscale and nanoscale features as well as hydrogen bonds network of lignocellulosic biomass. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd