• Open Access

RNAi suppression of lignin biosynthesis in sugarcane reduces recalcitrance for biofuel production from lignocellulosic biomass

Authors

  • Je Hyeong Jung,

    1. Agronomy Department, University of Florida, IFAS, Gainesville, FL, USA
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  • Walid M. Fouad,

    1. Agronomy Department, University of Florida, IFAS, Gainesville, FL, USA
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    • Present address: Department of Biology, School of Sciences and Engineering, The American University of Cairo, PO Box 74, AUC Avenue, SSE Building, Room 2184, New Cairo 11835, Egypt.

  • Wilfred Vermerris,

    1. Agronomy Department, University of Florida, IFAS, Gainesville, FL, USA
    2. Plant Molecular and Cellular Biology Program, University of Florida, IFAS, Gainesville, FL, USA
    3. University of Florida Genetics Institute, Gainesville, FL, USA
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  • Maria Gallo,

    1. Agronomy Department, University of Florida, IFAS, Gainesville, FL, USA
    2. Plant Molecular and Cellular Biology Program, University of Florida, IFAS, Gainesville, FL, USA
    3. University of Florida Genetics Institute, Gainesville, FL, USA
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  • Fredy Altpeter

    Corresponding author
    1. Agronomy Department, University of Florida, IFAS, Gainesville, FL, USA
    2. Plant Molecular and Cellular Biology Program, University of Florida, IFAS, Gainesville, FL, USA
    3. University of Florida Genetics Institute, Gainesville, FL, USA
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(fax +352-392-7248; email altpeter@ufl.edu)

Summary

Sugarcane is a prime bioethanol feedstock. Currently, sugarcane ethanol is produced through fermentation of the sucrose, which can easily be extracted from stem internodes. Processes for production of biofuels from the abundant lignocellulosic sugarcane residues will boost the ethanol output from sugarcane per land area. However, unlocking the vast amount of chemical energy stored in plant cell walls remains expensive primarily because of the intrinsic recalcitrance of lignocellulosic biomass. We report here the successful reduction in lignification in sugarcane by RNA interference, despite the complex and highly polyploid genome of this interspecific hybrid. Down-regulation of the sugarcane caffeic acid O-methyltransferase (COMT) gene by 67% to 97% reduced the lignin content by 3.9% to 13.7%, respectively. The syringyl/guaiacyl ratio in the lignin was reduced from 1.47 in the wild type to values ranging between 1.27 and 0.79. The yields of directly fermentable glucose from lignocellulosic biomass increased up to 29% without pretreatment. After dilute acid pretreatment, the fermentable glucose yield increased up to 34%. These observations demonstrate that a moderate reduction in lignin (3.9% to 8.4%) can reduce the recalcitrance of sugarcane biomass without compromising plant performance under controlled environmental conditions.

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