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Removal of Water-Soluble Extractives Improves the Enzymatic Digestibility of Steam-Pretreated Softwood Barks

Frankó, Balázs LU ; Carlqvist, Karin LU ; Galbe, Mats LU ; Lidén, Gunnar LU and Wallberg, Ola LU (2018) In Applied Biochemistry and Biotechnology 184(2). p.599-615
Abstract

Softwood bark contains a large amounts of extractives—i.e., soluble lipophilic (such as resin acids) and hydrophilic components (phenolic compounds, stilbenes). The effects of the partial removal of water-soluble extractives before acid-catalyzed steam pretreatment on enzymatic digestibility were assessed for two softwood barks—Norway spruce and Scots pine. A simple hot water extraction step removed more than half of the water-soluble extractives from the barks, which improved the enzymatic digestibility of both steam-pretreated materials. This effect was more pronounced for the spruce than the pine bark, as evidenced by the 30 and 11% glucose yield improvement, respectively, in the enzymatic digestibility. Furthermore, analysis of the... (More)

Softwood bark contains a large amounts of extractives—i.e., soluble lipophilic (such as resin acids) and hydrophilic components (phenolic compounds, stilbenes). The effects of the partial removal of water-soluble extractives before acid-catalyzed steam pretreatment on enzymatic digestibility were assessed for two softwood barks—Norway spruce and Scots pine. A simple hot water extraction step removed more than half of the water-soluble extractives from the barks, which improved the enzymatic digestibility of both steam-pretreated materials. This effect was more pronounced for the spruce than the pine bark, as evidenced by the 30 and 11% glucose yield improvement, respectively, in the enzymatic digestibility. Furthermore, analysis of the chemical composition showed that the acid-insoluble lignin content of the pretreated materials decreased when water-soluble extractives were removed prior to steam pretreatment. This can be explained by a decreased formation of water-insoluble “pseudo-lignin” from water-soluble bark phenolics during the acid-catalyzed pretreatment, which otherwise results in distorted lignin analysis and may also contribute to the impaired enzymatic digestibility of the barks. Thus, this study advocates the removal of extractives as the first step in the processing of bark or bark-rich materials in a sugar platform biorefinery.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Bark, Enzymatic saccharification, Extractives, Softwood, Steam pretreatment
in
Applied Biochemistry and Biotechnology
volume
184
issue
2
pages
599 - 615
publisher
Humana Press
external identifiers
  • scopus:85028539045
ISSN
0273-2289
DOI
10.1007/s12010-017-2577-2
language
English
LU publication?
yes
id
c616b322-19fb-4c43-a3e3-2e786c8b6d07
date added to LUP
2017-09-18 22:41:46
date last changed
2018-10-07 05:00:05
@article{c616b322-19fb-4c43-a3e3-2e786c8b6d07,
  abstract     = {<p>Softwood bark contains a large amounts of extractives—i.e., soluble lipophilic (such as resin acids) and hydrophilic components (phenolic compounds, stilbenes). The effects of the partial removal of water-soluble extractives before acid-catalyzed steam pretreatment on enzymatic digestibility were assessed for two softwood barks—Norway spruce and Scots pine. A simple hot water extraction step removed more than half of the water-soluble extractives from the barks, which improved the enzymatic digestibility of both steam-pretreated materials. This effect was more pronounced for the spruce than the pine bark, as evidenced by the 30 and 11% glucose yield improvement, respectively, in the enzymatic digestibility. Furthermore, analysis of the chemical composition showed that the acid-insoluble lignin content of the pretreated materials decreased when water-soluble extractives were removed prior to steam pretreatment. This can be explained by a decreased formation of water-insoluble “pseudo-lignin” from water-soluble bark phenolics during the acid-catalyzed pretreatment, which otherwise results in distorted lignin analysis and may also contribute to the impaired enzymatic digestibility of the barks. Thus, this study advocates the removal of extractives as the first step in the processing of bark or bark-rich materials in a sugar platform biorefinery.</p>},
  author       = {Frankó, Balázs and Carlqvist, Karin and Galbe, Mats and Lidén, Gunnar and Wallberg, Ola},
  issn         = {0273-2289},
  keyword      = {Bark,Enzymatic saccharification,Extractives,Softwood,Steam pretreatment},
  language     = {eng},
  number       = {2},
  pages        = {599--615},
  publisher    = {Humana Press},
  series       = {Applied Biochemistry and Biotechnology},
  title        = {Removal of Water-Soluble Extractives Improves the Enzymatic Digestibility of Steam-Pretreated Softwood Barks},
  url          = {http://dx.doi.org/10.1007/s12010-017-2577-2},
  volume       = {184},
  year         = {2018},
}