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Title: Structural Transformation of Isolated Poplar and Switchgrass Lignins from Dilute Acid Pretreatment

A key step in conversion of cellulosic biomass into sustainable fuels and chemicals is thermochemical pretreatment to reduce plant cell wall recalcitrance. Obtaining an improved understanding of the fundamental chemistry of lignin, the most recalcitrant component of biomass, during pretreatment is critical to the continued development of renewable biofuel production. To examine the intrinsic chemistry of lignin during dilute acid pretreatment (DAP), lignin was isolated from poplar and switchgrass using a cellulolytic enzyme system and then treated under DAP conditions. These results highlight that lignin is subjected to depolymerization reactions within the first 2 min of dilute acid pretreatment and these changes are accompanied by increased generation of aliphatic and phenolic hydroxyl groups of lignin. This is followed by a competing set of depolymerization and repolymerization reactions that lead to a decrease in the content of guaiacyl lignin units and an increase in condensed lignin units as the reaction residence time is extended beyond 5 min. Finally, we showed that a detailed comparison of changes in functional groups and molecular weights of cellulolytic enzyme lignins with different structural parameters, related to the recalcitrant properties of lignin, could be successfully altered during DAP conditions.
 [1] ;  [2] ;  [1] ;  [1] ;  [3]
  1. Georgia Inst. of Technology, Atlanta, GA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Sustainable Chemistry & Engineering
Additional Journal Information:
Journal Volume: 3; Journal Issue: 9; Journal ID: ISSN 2168-0485
American Chemical Society (ACS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
09 BIOMASS FUELS poplar; switchgrass; dilute acid pretreatment; cellulolytic enzyme lignin; reaction mechanism