Degradation of Carbohydrates during Dilute Sulfuric Acid Pretreatment Can Interfere with Lignin Measurements in Solid Residues

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Abstract

The lignin content measured after dilute sulfuric acid pretreatment of corn stover indicates more lignin than could be accounted for on the basis of the untreated corn stover lignin content. This phenomenon was investigated using a combination of 13C cross-polarization/magic-angle spinning (CP/MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy and lignin removal using acid chlorite bleaching. Only minimal contamination with carbohydrates and proteins was observed in the pretreated corn stover. Incorporating degradation products from sugars was also investigated using 13C-labeled sugars. The results indicate that sugar degradation products are present in the pretreatment residue and may be intimately associated with the lignin. Studies comparing whole corn stover (CS) to extractives-free corn stover [CS(Ext)] clearly demonstrated that extractives are a key contributor to the high-lignin mass balance closure (MBC). Sugars and other low molecular weight compounds present in plant extractives polymerize and form solids during pretreatment, resulting in apparent Klason lignin measurements that are biased high.

Original languageAmerican English
Pages (from-to)3286-3292
Number of pages7
JournalJournal of Agricultural and Food Chemistry
Volume61
Issue number13
DOIs
StatePublished - 3 Apr 2013

NREL Publication Number

  • NREL/JA-5100-57242

Keywords

  • compositional analysis
  • lignin
  • mass balance closure
  • pretreatment

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