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Elucidation of Changes in Cellulose Ultrastructure and Accessibility in Hardwood Fractionation Processes with Carbohydrate Binding Modules

Novy, Vera LU ; Nielsen, Fredrik LU ; Olsson, Johanna LU ; Aïssa, Kevin ; Saddler, Jack N. ; Wallberg, Ola LU and Galbe, Mats LU (2020) In ACS Sustainable Chemistry and Engineering 8(17). p.6767-6776
Abstract

We have recently presented a sequential treatment method, in which steam explosion (STEX) was followed by hydrotropic extraction (HEX), to selectively fractionate cellulose, hemicellulose, and lignin in hardwood into separate process streams. However, above a treatment severity threshold, the structural alterations in the cellulose-enriched fraction appeared to restrict the enzymatic hydrolyzability and delignification efficiency. To better understand the ultrastructural changes in the cellulose, hardwood chips were treated by single (STEX or HEX) and combined treatments (STEX and HEX), and the cellulose accessibility quantified with carbohydrate-binding modules (CBMs) that bind preferentially to crystalline (CBM2a) and paracrystalline... (More)

We have recently presented a sequential treatment method, in which steam explosion (STEX) was followed by hydrotropic extraction (HEX), to selectively fractionate cellulose, hemicellulose, and lignin in hardwood into separate process streams. However, above a treatment severity threshold, the structural alterations in the cellulose-enriched fraction appeared to restrict the enzymatic hydrolyzability and delignification efficiency. To better understand the ultrastructural changes in the cellulose, hardwood chips were treated by single (STEX or HEX) and combined treatments (STEX and HEX), and the cellulose accessibility quantified with carbohydrate-binding modules (CBMs) that bind preferentially to crystalline (CBM2a) and paracrystalline cellulose (CBM17). Fluorescent-tagged versions of the CBMs were used to map the spatial distribution of cellulose substructures with confocal laser scanning microscopy. With increasing severities, STEX increased the apparent crystallinity (CBM2a/CBM17-ratio) and overall accessibility (CBM2aH6 + CBM17) of the cellulose, whereas HEX demonstrated the opposite trend. The respective effects could also be discerned in the combined treatments where increasing severities further resulted in higher hemicellulose dissolution and, although initially beneficial, in stagnating accessibility and hydrolyzability. This study suggests that balancing the severities in the two treatments is required to maximize the fractionation and simultaneously achieve a reactive and accessible cellulose that is readily hydrolyzable.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
carbohydrate-binding modules, cellulose accessibility to enzymes, cellulose ultrastructure, fractionation, hardwood, hydrolyzability, hydrotropic extraction, steam pretreatment
in
ACS Sustainable Chemistry and Engineering
volume
8
issue
17
pages
10 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85084753238
  • pmid:32391215
ISSN
2168-0485
DOI
10.1021/acssuschemeng.9b07589
language
English
LU publication?
yes
id
40825878-9bae-4bf3-99ab-8605e6edc9d8
date added to LUP
2020-05-23 20:49:59
date last changed
2021-03-03 03:26:56
@article{40825878-9bae-4bf3-99ab-8605e6edc9d8,
  abstract     = {<p>We have recently presented a sequential treatment method, in which steam explosion (STEX) was followed by hydrotropic extraction (HEX), to selectively fractionate cellulose, hemicellulose, and lignin in hardwood into separate process streams. However, above a treatment severity threshold, the structural alterations in the cellulose-enriched fraction appeared to restrict the enzymatic hydrolyzability and delignification efficiency. To better understand the ultrastructural changes in the cellulose, hardwood chips were treated by single (STEX or HEX) and combined treatments (STEX and HEX), and the cellulose accessibility quantified with carbohydrate-binding modules (CBMs) that bind preferentially to crystalline (CBM2a) and paracrystalline cellulose (CBM17). Fluorescent-tagged versions of the CBMs were used to map the spatial distribution of cellulose substructures with confocal laser scanning microscopy. With increasing severities, STEX increased the apparent crystallinity (CBM2a/CBM17-ratio) and overall accessibility (CBM2aH6 + CBM17) of the cellulose, whereas HEX demonstrated the opposite trend. The respective effects could also be discerned in the combined treatments where increasing severities further resulted in higher hemicellulose dissolution and, although initially beneficial, in stagnating accessibility and hydrolyzability. This study suggests that balancing the severities in the two treatments is required to maximize the fractionation and simultaneously achieve a reactive and accessible cellulose that is readily hydrolyzable.</p>},
  author       = {Novy, Vera and Nielsen, Fredrik and Olsson, Johanna and Aïssa, Kevin and Saddler, Jack N. and Wallberg, Ola and Galbe, Mats},
  issn         = {2168-0485},
  language     = {eng},
  month        = {05},
  number       = {17},
  pages        = {6767--6776},
  publisher    = {The American Chemical Society (ACS)},
  series       = {ACS Sustainable Chemistry and Engineering},
  title        = {Elucidation of Changes in Cellulose Ultrastructure and Accessibility in Hardwood Fractionation Processes with Carbohydrate Binding Modules},
  url          = {http://dx.doi.org/10.1021/acssuschemeng.9b07589},
  doi          = {10.1021/acssuschemeng.9b07589},
  volume       = {8},
  year         = {2020},
}