Cellulosic Feedstock for Renewable Fuels - Prospective on Breeding

Authors: Anderson, William - Bill

Submitted to: American Forage and Grassland Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/21/2007
Publication Date: 1/29/2008
Citation: Anderson, W.F. 2008. Cellulosic feedstock for renewable fuels - prospective on breeding. [abstract]. American Forage and Grassland Conference , January 28-31, 2008, Louisville, Kentucky.

Interpretive Summary: not required

Technical Abstract: Modifying plants through breeding is one method of improving efficiency of dedicated feedstock for biofuels. Besides improving yield, distinct cell wall components or concentrations of minerals within the plant may need to be altered. There are two main processes for conversion of biomass feedstock to energy; 1) enzymatic conversion of cellulose and subsequent fermentation and 2) thermochemical conversion. For the sugar-based fermentation conversion, besides cellulose and lignin concentration changes, other traits that effect recalcitrance need to be determined. Certain ligno-cellulose linkages can negatively affect access of enzymes to degradable portions of the cell wall. Data indicates that there is potential of increasing conversion efficiency to ethanol and isolating co-products through breeding of germplasm with different genes. Studies have shown that breeding for improved rumen digestibility is often accompanied by changes in lignin, levels of phenolics, and ligno-cellulosic linkages in perennial grass species. For example, the highly digestible forage bermudagrass Coastcross 1 has fewer phenolic acid esters within the parenchyma bundle sheath compared to Coastal. Equally digestible Tifton 85, on the other hand, has shown to be less recalcitrant due to a higher ratio of enzyme degradable ester-linked phenolic acid linkages to non-degradable ether linkages. Increased knowledge of the genetic differences of cell wall components among specific cell types and among diverse grass germplasm is necessary to determine specific genes of interest. Slight changes in highly lignified, recalcitrant cell walls may not result in improved bioconversion, whereas changes in non-lignified cell walls could substantially increase the availability of substrates, thus enhancing release of sugars and co-products. The challenge is to modify cell walls to optimize their potential as substrates in the cellulose-to-ethanol biorefinery.