Genetic manipulation of lignin reduces recalcitrance and improves ethanol production from switchgrass

Chunxiang Fu, Jonathan R. Mielenz, Xirong Xiao, Yaxin Ge, Choo Y. Hamilton, Miguel Rodriguez, Fang Chen, Marcus Foston, Arthur Ragauskas, Joseph Bouton, Richard A. Dixon, Zeng Yu Wang

Research output: Contribution to journalArticlepeer-review

575 Scopus citations

Abstract

Switchgrass is a leading dedicated bioenergy feedstock in the United States because it is a native, high-yielding, perennial prairie grass with a broad cultivation range and low agronomic input requirements. Biomass conversion research has developed processes for production of ethanol and other biofuels, but they remain costly primarily because of the intrinsic recalcitrance of biomass. We show here that genetic modification of switchgrass can produce phenotypically normal plants that have reduced thermal-chemical (≤180 °C), enzymatic, and microbial recalcitrance. Down-regulation of the switchgrass caffeic acid O-methyltransferase gene decreases lignin content modestly, reduces the syringyl:guaiacyl lignin monomer ratio, improves forage quality, and, most importantly, increases the ethanol yield by up to 38%using conventional biomass fermentation processes. The down-regulated lines require less severe pretreatment and 300-400% lower cellulase dosages for equivalent product yields using simultaneous saccharification and fermentation with yeast. Furthermore, fermentation of diluted acid-pretreated transgenic switchgrass using Clostridium thermocellum with no added enzymes showed better product yields than obtained with unmodified switchgrass. Therefore, this apparent reduction in the recalcitrance of transgenic switchgrass has the potential to lower processing costs for biomass fermentation-derived fuels and chemicals significantly. Alternatively, such modified transgenic switch-grass lines should yield significantly more fermentation chemicals per hectare under identical process conditions.

Original languageEnglish
Pages (from-to)3803-3808
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number9
DOIs
StatePublished - Mar 1 2011

Keywords

  • Biofuel crop
  • Cellulosic ethanol
  • Lignin modification
  • Panicum virgatum

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