skip to main content

DOE PAGESDOE PAGES

Title: Effect of lignin content on changes occurring in poplar cellulose ultrastructure during dilute acid pretreatment

Obtaining a better understanding of the complex mechanisms occurring during lignocellulosic deconstruction is critical to the continued growth of renewable biofuel production. A key step in bioethanol production is thermochemical pretreatment to reduce plant cell wall recalcitrance for downstream processes. Previous studies of dilute acid pretreatment (DAP) have shown significant changes in cellulose ultrastructure that occur during pretreatment, but there is still a substantial knowledge gap with respect to the influence of lignin on these cellulose ultrastructural changes. This study was designed to assess how the presence of lignin influences DAP-induced changes in cellulose ultrastructure, which might ultimately have large implications with respect to enzymatic deconstruction efforts. Native, untreated hybrid poplar (Populus trichocarpa x Populus deltoids) samples and a partially delignified poplar sample (facilitated by acidic sodium chlorite pulping) were separately pretreated with dilute sulfuric acid (0.10 M) at 160°C for 15 minutes and 35 minutes, respectively . Following extensive characterization, the partially delignified biomass displayed more significant changes in cellulose ultrastructure following DAP than the native untreated biomass. With respect to the native untreated poplar, delignified poplar after DAP (in which approximately 40% lignin removal occurred) experienced: increased cellulose accessibility indicated by increased Simons’ stain (orange dye) adsorption frommore » 21.8 to 72.5 mg/g, decreased cellulose weight-average degree of polymerization (DPw) from 3087 to 294 units, and increased cellulose crystallite size from 2.9 to 4.2 nm. These changes following DAP ultimately increased enzymatic sugar yield from 10 to 80%. We conclude that, overall, the results indicate a strong influence of lignin content on cellulose ultrastructural changes occurring during DAP. With the reduction of lignin content during DAP, the enlargement of cellulose microfibril dimensions and crystallite size becomes more apparent. Further, this enlargement of cellulose microfibril dimensions is attributed to specific processes, including the co-crystallization of crystalline cellulose driven by irreversible inter-chain hydrogen bonding (similar to hornification) and/or cellulose annealing that converts amorphous cellulose to paracrystalline and crystalline cellulose. Essentially, lignin acts as a barrier to prevent cellulose crystallinity increase and cellulose fibril coalescence during DAP.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [3] ;  [3] ;  [4] ;  [5] ;  [3] ;  [6] ;  [5]
  1. Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemistry and Biochemistry
  2. Washington Univ., St. Louis, MO (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Structural Molecular Biology (CSMB)
  4. Univ. of California, Riverside, CA (United States). Bourns College of Engineering
  5. Univ. of California, Riverside, CA (United States). Bourns College of Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC)
  6. Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemistry and Biochemistry; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
OSTI Identifier:
1259860
Grant/Contract Number:
FWP ERKP752; FWP ERKP291
Type:
Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 1754-6834
Publisher:
BioMed Central
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES Cellulose ultrastructure; Lignin content; Dilute acid pretreatment; Delignification; Enzymatic sugar release; Biomass recalcitrance