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

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

Silencing CHALCONE SYNTHASE in Maize Impedes the Incorporation of Tricin into Lignin and Increases Lignin Content

“…The cell wall polysaccharide fraction, which constitutes roughly 75% of the total lignocellulosic mass, can be converted into fermentable sugars (Wilke et al, 1981;Vanholme et al, 2013a;Marriott et al, 2016). However, the compact structure and complex chemical composition of the plant cell wall negatively affect the enzymatic digestibility of the biomass, a feature known as biomass recalcitrance (Zhao et al, 2012). Several factors limit the enzymatic degradation, such as carbohydratelignin cross-linking and, especially, the presence of the aromatic polymer lignin (Chen and Dixon, 2007;Grabber et al, 2008;Van Acker et al, 2013;Vermerris and Abril, 2015;Wang et al, 2015a).…”

Hot water treatment of hardwood kraft pulp produces high-purity cellulose and polymeric xylan

“…5b), with values between 100-150 mL/g at about 7% xylan content, much lower than those required in commercial dissolving applications. The low intrinsic viscosity of the bleached water-treated pulps is due to the lower initial viscosity, although it is also possible that, compared to bleached pulps, the presence of residual lignin in the unbleached pulps played some role in protecting the cellulose fraction from hydrolytic degradation during the HWT (Zhao et al 2012). Commercial dissolving pulps used in the manufacture of cellulose derivatives such as viscose need to be fully bleached.…”

Continuous succinic acid production from xylose by Actinobacillus succinogenes

“…Xylose is a major carbohydrate in hemicellulose, and the xylan polymer constitutes between 20% and 50% of grassy biomass, and 8% to 25% of woody biomass [28]. Furthermore, current promising pretreatment technologies are able to generate xylose-rich hydrolysates from corn stover, a model lignocellulosic feedstock [29][30][31].…”