Changes in Lignin and Polysaccharide Components in 13 Cultivars of Rice Straw following Dilute Acid Pretreatment as Studied by Solution-State 2D 1H-13C NMR

PLoS One. 2015 Jun 17;10(6):e0128417. doi: 10.1371/journal.pone.0128417. eCollection 2015.

Abstract

A renewable raw material, rice straw is pretreated for biorefinery usage. Solution-state two-dimensional (2D) 1H-13 C hetero-nuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy, was used to analyze 13 cultivars of rice straw before and after dilute acid pretreatment, to characterize general changes in the lignin and polysaccharide components. Intensities of most (15 of 16) peaks related to lignin aromatic regions, such as p-coumarate, guaiacyl, syringyl, p-hydroxyphenyl, and cinnamyl alcohol, and methoxyl, increased or remained unchanged after pretreatment. In contrast, intensities of most (11 of 13) peaks related to lignin aliphatic linkages or ferulate decreased. Decreased heterogeneity in the intensities of three peaks related to cellulose components in acid-insoluble residues resulted in similar glucose yield (0.45-0.59 g/g-dry biomass). Starch-derived components showed positive correlations (r = 0.71 to 0.96) with glucose, 5-hydroxymethylfurfural (5-HMF), and formate concentrations in the liquid hydrolysates, and negative correlations (r = -0.95 to -0.97) with xylose concentration and acid-insoluble residue yield. These results showed the fate of lignin and polysaccharide components by pretreatment, suggesting that lignin aromatic regions and cellulose components were retained in the acid insoluble residues and starch-derived components were transformed into glucose, 5-HMF, and formate in the liquid hydrolysate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acids / chemistry*
  • Biomass
  • Carbon-13 Magnetic Resonance Spectroscopy
  • Cellulase / metabolism
  • Formates / analysis
  • Furaldehyde / analogs & derivatives
  • Furaldehyde / analysis
  • Glucose / analysis
  • Hydrolysis
  • Lignin / chemistry*
  • Lignin / metabolism
  • Oryza / chemistry
  • Oryza / metabolism*
  • Plant Stems / chemistry
  • Plant Stems / metabolism
  • Polysaccharides / chemistry*
  • Polysaccharides / metabolism
  • Solutions / chemistry

Substances

  • Acids
  • Formates
  • Polysaccharides
  • Solutions
  • formic acid
  • 5-hydroxymethylfurfural
  • Lignin
  • Furaldehyde
  • Cellulase
  • Glucose

Grants and funding

This work was supported by the Ministry of Education, Culture, Sports, Science and Technology, Japan, through the NC-CARP Project, http://nc-carp.org/, and the Ministry of Education, Culture, Sports, Science and Technology, through the Japan Innovative Bioproduction Kobe, http://www.org.kobe-u.ac.jp/bioproduction/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.