Ethanol yields and cell wall properties in divergently bred switchgrass genotypes.

Genetic modification of herbaceous plant cell walls to increase biofuels yields is a primary bioenergy research goal. Using two switchgrass populations developed by divergent breeding for ruminant digestibility, the contributions of several wall-related factors to ethanol yields was evaluated. Field grown low lignin plants significantly out yielded high lignin plants for conversion to ethanol by 39.1% and extraction of xylans by 12%. However, across all plants analyzed, greater than 50% of the variation in ethanol yields was attributable to changes in tissue and cell wall architecture, and responses of stem biomass to dilute-acid pretreatment. Although lignin levels were lower in the most efficiently converted genotypes, no apparent correlation were seen in the lignin monomer G/S ratios. Plants with higher ethanol yields were associated with an apparent decrease in the lignification of the cortical sclerenchyma, and a marked decrease in the granularity of the cell walls following dilute-acid pretreatment.

[1]  R. Wu,et al.  Complete Switchgrass Genetic Maps Reveal Subgenome Collinearity, Preferential Pairing and Multilocus Interactions , 2010, Genetics.

[2]  Gautam Sarath,et al.  Internode structure and cell wall composition in maturing tillers of switchgrass (Panicum virgatum. L). , 2007, Bioresource technology.

[3]  Joseph A. Rollin,et al.  Increasing cellulose accessibility is more important than removing lignin: A comparison of cellulose solvent‐based lignocellulose fractionation and soaking in aqueous ammonia , 2011, Biotechnology and bioengineering.

[4]  M. Cotta,et al.  Improved Sugar Conversion and Ethanol Yield for Forage Sorghum (Sorghum bicolor L. Moench) Lines with Reduced Lignin Contents , 2009, BioEnergy Research.

[5]  K. Vogel,et al.  Cell-Wall Composition and Accessibility to Hydrolytic Enzymes is Differentially Altered in Divergently Bred Switchgrass (Panicum virgatum L.) Genotypes , 2008, Applied biochemistry and biotechnology.

[6]  Robert A. Graybosch,et al.  Opportunities and roadblocks in utilizing forages and small grains for liquid fuels , 2008, Journal of Industrial Microbiology & Biotechnology.

[7]  M. Thrash,et al.  Comparison of different pretreatment methods based on residual lignin effect on the enzymatic hydrolysis of switchgrass. , 2010, Bioresource technology.

[8]  Zengyu Wang,et al.  Lignin deposition and associated changes in anatomy, enzyme activity, gene expression, and ruminal degradability in stems of tall fescue at different developmental stages. , 2002, Journal of agricultural and food chemistry.

[9]  R. Dixon,et al.  Genetic manipulation of lignin reduces recalcitrance and improves ethanol production from switchgrass , 2011, Proceedings of the National Academy of Sciences.

[10]  Chris Somerville,et al.  Cellulosic biofuels. , 2009, Annual review of plant biology.

[11]  J. Vogel.  Unique aspects of the grass cell wall. , 2008, Current opinion in plant biology.

[12]  J. Ralph,et al.  Cell wall fermentation kinetics are impacted more by lignin content and ferulate cross-linking than by lignin composition , 2009 .

[13]  Xirong Xiao,et al.  Downregulation of Cinnamyl Alcohol Dehydrogenase (CAD) Leads to Improved Saccharification Efficiency in Switchgrass , 2011, BioEnergy Research.

[14]  S. Sattler,et al.  Genetic background impacts soluble and cell wall-bound aromatics in brown midrib mutants of sorghum , 2008, Planta.

[15]  Hansang Jung,et al.  Relationships of fibre, lignin, and phenolics to in vitro fibre digestibility in three perennial grasses , 2006 .

[16]  Maureen C. McCann,et al.  Genetic Resources for Maize Cell Wall Biology1[C][W][OA] , 2009, Plant Physiology.

[17]  B. Dien,et al.  Downregulation of Cinnamyl-Alcohol Dehydrogenase in Switchgrass by RNA Silencing Results in Enhanced Glucose Release after Cellulase Treatment , 2011, PloS one.

[18]  N. Carpita,et al.  Designing the deconstruction of plant cell walls. , 2008, Current opinion in plant biology.

[19]  Steven R. Thomas,et al.  Investigation of enzyme formulation on pretreated switchgrass. , 2011, Bioresource technology.

[20]  Mark F. Davis,et al.  Lignin content in natural Populus variants affects sugar release , 2011, Proceedings of the National Academy of Sciences.

[21]  A. Ragauskas,et al.  Correlation between anatomical characteristics of ethanol organosolv pretreated Buddleja davidii and its enzymatic conversion to glucose , 2010, Biotechnology and bioengineering.

[22]  M. Himmel,et al.  Visualizing lignin coalescence and migration through maize cell walls following thermochemical pretreatment , 2008, Biotechnology and bioengineering.

[23]  M. M. D. O. Buanafina,et al.  Expression of a fungal ferulic acid esterase increases cell wall digestibility of tall fescue (Festuca arundinacea). , 2008, Plant biotechnology journal.

[24]  R. Perrin,et al.  Net energy of cellulosic ethanol from switchgrass , 2008, Proceedings of the National Academy of Sciences.

[25]  Steven R. Thomas,et al.  Surface and ultrastructural characterization of raw and pretreated switchgrass. , 2011, Bioresource technology.

[26]  Ratna R. Sharma-Shivappa,et al.  Dilute Acid Pretreatment of Oven-dried Switchgrass Germplasms for Bioethanol Production , 2009 .

[27]  Y. Barrière,et al.  In search of a maize ideotype for cell wall enzymatic degradability using histological and biochemical lignin characterization. , 2005, Journal of agricultural and food chemistry.

[28]  K. Moore,et al.  Winter Survival in Switchgrass Populations Bred for High IVDMD , 2002 .

[29]  B. Simmons,et al.  Comparison of dilute acid and ionic liquid pretreatment of switchgrass: Biomass recalcitrance, delignification and enzymatic saccharification. , 2010, Bioresource technology.

[30]  Robert B. Mitchell,et al.  Chemical composition and response to dilute-acid pretreatment and enzymatic saccharification of alfalfa, reed canarygrass, and switchgrass , 2006 .

[31]  Hugh O'Neill,et al.  Breakdown of cell wall nanostructure in dilute acid pretreated biomass. , 2010, Biomacromolecules.

[32]  W. Boerjan,et al.  Lignin biosynthesis. , 2003, Annual review of plant biology.

[33]  K. Moore,et al.  Predicted and Realized Gains from Selection for In Vitro Dry Matter Digestibility and Forage Yield in Switchgrass , 1993 .

[34]  D. Buxton,et al.  Genetic modification of lignin concentration affects fitness of perennial herbaceous plants , 2002, Theoretical and Applied Genetics.