Autohydrolysis and aqueous ammonia extraction of wheat straw: effect of treatment severity on yield and structure of hemicellulose and lignin

Mika Sipponen, Ville Pihlajaniemi, Satu Sipponen, Ossi Pastinen, Simo Laakso

Research output: Contribution to journalArticleScientificpeer-review

21 Citations (Scopus)
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Abstract

The objective of this study was to elucidate the impact of autohydrolysis severity on the yield and structure of wheat straw hemicellulose and lignin. The autohydrolysis treatments were carried out at maximum temperatures between 170 °C and 200 °C. The autohydrolysis liquors were separated and the solids were successively extracted with aqueous ammonia either in moderate or high intensity extraction conditions to dissolve lignin for analysis. Increasing autohydrolysis severity decreased the molar mass of the aqueous ammonia extracts from 5450 g mol−1 to 1810 g mol−1, and carbohydrate content from 6% to 0.1%. The optimum autohydrolysis severity (log R0 = 3.81) for xylan recovery released mainly oligomeric arabinoxylans at 66% xylan recovery yield. Drastic degradation of pentoses occurred beyond the optimum severity. As an indication of accumulation of “pseudo-lignin” during autohydrolysis, decreasing relative aromaticity in the aqueous ammonia extracts as a function of autohydrolysis severity was shown. The finding was confirmed by quantitative analysis of the cupric oxide oxidation products of lignin suggesting up to 55% decrease in the relative amount of native lignin at the highest severity. These results show the importance of distinguishing between lignin and “pseudo-lignin” in fractions obtained from lignocellulosic materials subjected to acidic pretreatment.
Original languageEnglish
Pages (from-to)23177-23184
JournalRSC Advances
Volume4
Issue number4
DOIs
Publication statusPublished - 2014
MoE publication typeA1 Journal article-refereed

Keywords

  • Autohydrolysis
  • Degradation
  • Hemicellulose
  • Lignin
  • Severity
  • Wheat straw

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