Abstract
Efficient utilization of lignocellulosic Miscanthus biomass for the production of biochemicals, such as ethanol, is challenging due to its recalcitrance, which is influenced by the individual plant cell wall polymers and their interactions. Lignocellulosic biomass composition differs depending on several factors, such as plant age, harvest date, organ type, and genotype. Here, four selected Miscanthus genotypes (Miscanthus sinensis, Miscanthus sacchariflorus, Miscanthus × giganteus, Miscanthus sinensis × Miscanthus sacchariflorus hybrid) were grown and harvested, separated into stems and leaves, and characterized for their non‐starch polysaccharide composition and structures, lignin contents and structures, and hydroxycinnamate profiles (monomers and ferulic acid dehydrodimers). Polysaccharides of all genotypes are mainly composed of cellulose and low‐substituted arabinoxylans. Ratios of hemicelluloses to cellulose were comparable, with the exception of Miscanthus sinensis that showed a higher hemicellulose/cellulose ratio. Lignin contents of Miscanthus stems were higher than those of Miscanthus leaves. Considering the same organs, the four genotypes did not differ in their Klason lignin contents, but Miscanthus × giganteus showed the highest acetylbromide soluble lignin content. Lignin polymers isolated from stems varied in their S/G ratios and linkage type distributions across genotypes. p‐Coumaric acid was the most abundant ester‐bound hydroxycinnamte monomer in all samples. Ferulic acid dehydrodimers were analyzed as cell wall cross‐links, with 8‐5‐coupled diferulic acid being the main dimer, followed by 8‐O‐4‐, and 5‐5‐diferulic acid. Contents of p‐coumaric acid, ferulic acid, and ferulic acid dimers varied depending on genotype and organ type. The largest amount of cell wall cross‐links was analyzed for Miscanthus sinensis.
Highlights
There is an increasing interest in using biomass from fast growing non‐food perennial grasses as renewable resource
H2SO4 hydrolysis of stem polysaccharides resulted in slightly higher portions of glucose compared to glucose portions of leaf polysaccharides, suggesting higher cellulose portions in Miscanthus stems, which was already shown for different Miscanthus sinensis genotypes (Van der Weijde et al, 2017)
Different parts of the Miscanthus plant and different genotypes (Miscanthus sacchariflorus, Miscanthus sinensis × Miscanthus sacchariflorus hybrid, Miscanthus × giganteus, Miscanthus sinensis “Goliath”) were shown to partially differ in the overall cell wall composition and in structural details of the cell wall polymers demonstrating some genetic variability of Miscanthus
Summary
There is an increasing interest in using biomass from fast growing non‐food perennial grasses as renewable resource. Cell walls of grasses are mainly composed of cellulose, hemicelluloses (arabinoxylans and mixed‐linked β‐glucans in particular grasses), and lignin (Vogel, 2008) Hydroxycinnamates, such as ferulic and p‐coumaric acids are bound to polysaccharides and lignin. A few authors report some structural details such as lignin monomer composition and/ or lignin linkage type profiles (Cheng, Sorek, Zimmermann, Wemmer, & Pauly, 2013; Le Ngoc Huyen, Rémond, Dheilly, & Chabbert, 2010; Villaverde, Li, Ek, Ligero, & Vega, 2009), and acetylation degree of polysaccharides (Van der Weijde et al, 2017) These data are mostly limited to Miscanthus × giganteus. Studies on structural details of cell wall polymers such as lignin linkage type profiles and ferulic acid dehydrodimer contents specific to other Miscanthus genotypes are rarely available. We analyzed four Miscanthus genotypes for their cell wall composition, and all relevant polymers were characterized in detail
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