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Understanding the impact of steam pretreatment severity on cellulose ultrastructure, recalcitrance, and hydrolyzability of Norway spruce

Caputo, Fabio ; Al-Rudainy, Basel LU ; Naidjonoka, Polina ; Wallberg, Ola LU orcid ; Olsson, Lisbeth and Novy, Vera (2022) In Biomass Conversion and Biorefinery
Abstract

The
efficient use of softwood in biorefineries requires harsh pretreatment
conditions to overcome biomass recalcitrance. Following harsh
pretreatments, the hemicellulose is solubilized. Here, we studied the
material characteristics of Norway spruce following steam pretreatment
at six different severities, relating chemical and structural
information to the enzymatic hydrolyzability. Steam pretreatment
conditions were defined by two different temperatures (180 °C and
210 °C), with and without the addition of various acids (CH3COOH, H3PO4, H2SO4, SO2). Structural knowledge of the streams is a cornerstone for developing an efficient... (More)

The
efficient use of softwood in biorefineries requires harsh pretreatment
conditions to overcome biomass recalcitrance. Following harsh
pretreatments, the hemicellulose is solubilized. Here, we studied the
material characteristics of Norway spruce following steam pretreatment
at six different severities, relating chemical and structural
information to the enzymatic hydrolyzability. Steam pretreatment
conditions were defined by two different temperatures (180 °C and
210 °C), with and without the addition of various acids (CH3COOH, H3PO4, H2SO4, SO2). Structural knowledge of the streams is a cornerstone for developing an efficient saccharification process.

This
study combines advanced structural characterizations to gain
fundamental understanding of the influence of severity of pretreatment
on spruce. Structural knowledge is a cornerstone in developing an
effective saccharification process by modulating pretreatment conditions
and enzymes employed.

Overall structural properties were assessed
by scanning electron microscopy. The effect of stream pretreatment
severity on lignin and lignin-carbohydrate bonds was investigated by
two-dimensional heteronuclear single quantum correlation nuclear
magnetic resonance. Finally, cellulose ultrastructure was studied by
applying small/wide-angle X-ray scattering. The structural
characteristics of the six pretreated softwood substrates were related
to the enzymatic hydrolyzability.

With increasing pretreatment
severity, surface defibrillation, and lignin depolymeryzation were
observed. Further, lignin-carbohydrate complexes signals were detected.
Cellulose analysis revealed the rearrangement of microfibrils leading to
the formation of larger microfibril aggregates. This microfibril
rearrangement likely contributed to the observed increase in enzymatic
hydrolysis yields as better enzyme accessibility resulted.

(Less)
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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
cellulose accessibility, SEM, SAXS/WAXS, 2D HSQC-NMR, Lignin carbohydrate bonds, Softwood
in
Biomass Conversion and Biorefinery
publisher
Springer
external identifiers
  • scopus:85142425853
ISSN
2190-6823
DOI
10.1007/s13399-022-03405-0
project
Intensification of the softwood-to-ethanol processes – design of efficient enzymatic hydrolysis combined with mild steam pretreatment
language
English
LU publication?
yes
id
b2bfef94-9d02-4fc4-b075-a296d6af23f2
date added to LUP
2022-11-24 17:24:10
date last changed
2023-12-20 03:00:01
@article{b2bfef94-9d02-4fc4-b075-a296d6af23f2,
  abstract     = {{<p>The <br>
efficient use of softwood in biorefineries requires harsh pretreatment <br>
conditions to overcome biomass recalcitrance. Following harsh <br>
pretreatments, the hemicellulose is solubilized. Here, we studied the <br>
material characteristics of Norway spruce following steam pretreatment <br>
at six different severities, relating chemical and structural <br>
information to the enzymatic hydrolyzability. Steam pretreatment <br>
conditions were defined by two different temperatures (180 °C and <br>
210 °C), with and without the addition of various acids (CH<sub>3</sub>COOH, H<sub>3</sub>PO<sub>4</sub>, H<sub>2</sub>SO<sub>4,</sub> SO<sub>2</sub>). Structural knowledge of the streams is a cornerstone for developing an efficient saccharification process.</p><p>This<br>
 study combines advanced structural characterizations to gain <br>
fundamental understanding of the influence of severity of pretreatment <br>
on spruce. Structural knowledge is a cornerstone in developing an <br>
effective saccharification process by modulating pretreatment conditions<br>
 and enzymes employed.</p><p>Overall structural properties were assessed<br>
 by scanning electron microscopy. The effect of stream pretreatment <br>
severity on lignin and lignin-carbohydrate bonds was investigated by <br>
two-dimensional heteronuclear single quantum correlation nuclear <br>
magnetic resonance. Finally, cellulose ultrastructure was studied by <br>
applying small/wide-angle X-ray scattering. The structural <br>
characteristics of the six pretreated softwood substrates were related <br>
to the enzymatic hydrolyzability.</p><p>With increasing pretreatment <br>
severity, surface defibrillation, and lignin depolymeryzation were <br>
observed. Further, lignin-carbohydrate complexes signals were detected. <br>
Cellulose analysis revealed the rearrangement of microfibrils leading to<br>
 the formation of larger microfibril aggregates. This microfibril <br>
rearrangement likely contributed to the observed increase in enzymatic <br>
hydrolysis yields as better enzyme accessibility resulted.</p>}},
  author       = {{Caputo, Fabio and Al-Rudainy, Basel and Naidjonoka, Polina and Wallberg, Ola and Olsson, Lisbeth and Novy, Vera}},
  issn         = {{2190-6823}},
  keywords     = {{cellulose accessibility; SEM; SAXS/WAXS; 2D HSQC-NMR; Lignin carbohydrate bonds; Softwood}},
  language     = {{eng}},
  month        = {{11}},
  publisher    = {{Springer}},
  series       = {{Biomass Conversion and Biorefinery}},
  title        = {{Understanding the impact of steam pretreatment severity on cellulose ultrastructure, recalcitrance, and hydrolyzability of Norway spruce}},
  url          = {{http://dx.doi.org/10.1007/s13399-022-03405-0}},
  doi          = {{10.1007/s13399-022-03405-0}},
  year         = {{2022}},
}