Lignin Content in Natural Populus Variants Affects Sugar Release

Mark Davis, Michael Studer, Jaclyn DeMartini, Brian Davison, Martin Keller, Gerald Tuskan, Charles Wyman, Robert Sykes

Research output: Contribution to journalArticlepeer-review

512 Scopus Citations

Abstract

The primary obstacle to producing renewable fuels from lignocellulosic biomass is a plant's recalcitrance to releasing sugars bound in the cell wall. From a sample set of wood cores representing 1,100 individual undomesticated Populus trichocarpa trees, 47 extreme phenotypes were selected across measured lignin content and ratio of syringyl and guaiacyl units (S/G ratio). This subset was tested for total sugar release through enzymatic hydrolysis alone as well as through combined hot-water pretreatment and enzymatic hydrolysis using a high-throughput screening method. The total amount of glucan and xylan released varied widely among samples, with total sugar yields of up to 92% of the theoretical maximum. A strong negative correlation between sugar release and lignin content was only found for pretreated samples with an S/G ratio < 2.0. For higher S/G ratios, sugar release was generally higher, and the negative influence of lignin was less pronounced. When examined separately, only glucose release was correlated with lignin content and S/G ratio in this manner, whereas xylose release depended on the S/G ratio alone. For enzymatic hydrolysis without pretreatment, sugar release increased significantly with decreasing lignin content below 20%, irrespective of the S/G ratio. Furthermore, certain samples featuring average lignin content and S/G ratios exhibited exceptional sugar release. These facts suggest that factors beyond lignin and S/G ratio influence recalcitrance to sugar release and point to a critical need for deeper understanding of cell-wall structure before plants can be rationally engineered for reduced recalcitrance and efficient biofuels production.

Original languageAmerican English
Pages (from-to)6300-6305
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number15
DOIs
StatePublished - 12 Apr 2011

NREL Publication Number

  • NREL/JA-2700-72008

Keywords

  • glucan
  • lignin
  • sugar
  • xylan
  • xylose

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