Grasses are highly productive and easier to breakdown than woody biomass. Improving biomass quality parameters is a key focus for the development of plants with enhanced conversion properties for use in future biorefineries. However, the composition of biomass feedstocks themselves is variable and may also be bioengineered for altered cell wall architecture. Much effort has gone into finding optimal processes for feedstock digestion. Barriers to cell wall deconstruction include the heterogeneous, cross-linked, nature of the cell wall, the crystalline nature of the cellulose that prevents enzyme access, the variety of covalent and hydrogen bonded linkages that must be cleaved, feedback inhibition of the products of hydrolysis, and the presence of enzymatic inhibitors including furans produced by thermochemical breakdown of sugars, phenolic compounds, and carboxylic acids. Currently several different pretreatment and enzymatic saccharification technologies are undergoing evaluation for the hydrolysis of structural carbohydrates into fermentable sugars. Though grasses are less recalcitrant than woody perennials, slow digestion rates and requirements for substantial quantities of cell wall degrading enzymes add significant process costs and inefficiencies. Recalcitrance of biomass to enzymatic digestion reduces the efficiencies of processes that utilize fermentable sugars from lignocellulosic material for the production of ethanol and other biofuels. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. No additional external funding was received for this study. This work was supported by the USDA Agricultural Research Service National Program 307 (Bioenergy) involving CRIS numbers: 5325-21000-028-00. Department of Energy grant number DE-AI02-09ER64829. Saathoff was supported in part by the Office of Science (BER), U. This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.įunding: Aaron J. Received: SeptemAccepted: DecemPublished: January 27, 2011 PLoS ONE 6(1):Įditor: Alfredo Herrera-Estrella, Cinvestav, Mexico When stained with the lignin and cutin specific stain phloroglucinol-HCl the staining intensity of one line indicated greater incorporation of hydroxycinnamyl aldehydes in the lignin.Ĭitation: Saathoff AJ, Sarath G, Chow EK, Dien BS, Tobias CM (2011) Downregulation of Cinnamyl-Alcohol Dehydrogenase in Switchgrass by RNA Silencing Results in Enhanced Glucose Release after Cellulase Treatment. Glucose release from ground samples pretreated with ammonium hydroxide and digested with cellulases was greater than in control transformants. CAD activity against coniferaldehyde, and sinapaldehyde in stems of silenced lines was significantly reduced as was overall lignin and cutin.
The resulting primary transformants accumulated less CAD RNA transcript and protein than control transformants and were demonstrated to be stably transformed with between 1 and 5 copies of the T-DNA. “Alamo” with an inverted repeat construct containing a fragment derived from the coding sequence of PviCAD2. To ascertain the effect of CAD downregulation in switchgrass, RNA mediated silencing of CAD was induced through Agrobacterium mediated transformation of cv.
Cinnamyl alcohol dehydrogenase (CAD) catalyzes the last step in monolignol biosynthesis and genetic evidence indicates CAD deficiency in grasses both decreases overall lignin, alters lignin structure and increases enzymatic recovery of sugars.
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