Enhanced characteristics of genetically modified switchgrass (Panicum virgatum L.) for high biofuel production

Biotechnology for Biofuels

Hui Shen²  Charleson R Poovaiah²  Angela Ziebell²  Timothy J Tschaplinski²  Sivakumar Pattathil²  Erica Gjersing²  Nancy L Engle²  Rui Katahira¹  Yunqiao Pu²  Robert Sykes²  Fang Chen²  Arthur J Ragauskas²  Jonathan R Mielenz²  Michael G Hahn²  Mark Davis²  C Neal Stewart²  Richard A Dixon¹ 

[1] Present address: Department of Biological Sciences, University of North Texas, 1155 Union Circle, Denton, TX 76203, USA

[2] BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA

关键词: Pectin;    Hemicellulose;    Lignin;    Recalcitrance;    Cell wall;    Transcription factor;    PvMYB4;    Cellulosic ethanol;    Feedstock;    Biofuel;    Bioenergy;    Switchgrass;   

Others  :  798052
DOI  :  10.1186/1754-6834-6-71

 received in 2013-02-07, accepted in 2013-04-30,  发布年份 2013

【 摘 要 】

Background

Lignocellulosic biomass is one of the most promising renewable and clean energy resources to reduce greenhouse gas emissions and dependence on fossil fuels. However, the resistance to accessibility of sugars embedded in plant cell walls (so-called recalcitrance) is a major barrier to economically viable cellulosic ethanol production. A recent report from the US National Academy of Sciences indicated that, “absent technological breakthroughs”, it was unlikely that the US would meet the congressionally mandated renewable fuel standard of 35 billion gallons of ethanol-equivalent biofuels plus 1 billion gallons of biodiesel by 2022. We here describe the properties of switchgrass (Panicum virgatum) biomass that has been genetically engineered to increase the cellulosic ethanol yield by more than 2-fold.

Results

We have increased the cellulosic ethanol yield from switchgrass by 2.6-fold through overexpression of the transcription factor PvMYB4. This strategy reduces carbon deposition into lignin and phenolic fermentation inhibitors while maintaining the availability of potentially fermentable soluble sugars and pectic polysaccharides. Detailed biomass characterization analyses revealed that the levels and nature of phenolic acids embedded in the cell-wall, the lignin content and polymer size, lignin internal linkage levels, linkages between lignin and xylans/pectins, and levels of wall-bound fucose are all altered in PvMYB4-OX lines. Genetically engineered PvMYB4-OX switchgrass therefore provides a novel system for further understanding cell wall recalcitrance.

Conclusions

Our results have demonstrated that overexpression of PvMYB4, a general transcriptional repressor of the phenylpropanoid/lignin biosynthesis pathway, can lead to very high yield ethanol production through dramatic reduction of recalcitrance. MYB4-OX switchgrass is an excellent model system for understanding recalcitrance, and provides new germplasm for developing switchgrass cultivars as biomass feedstocks for biofuel production.

【 授权许可】

   
2013 Shen et al.; licensee BioMed Central Ltd.

【 图 表 】

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