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Title: Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production


No abstract prepared.

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Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Science; Journal Volume: 315; Journal Issue: 9 February 2007
Country of Publication:
United States

Citation Formats

Himmel, M. E., Ding, S. Y., Johnson, D. K., Adney, W. S., Nimlos, M. R., Brady, J. W., and Foust, T. D. Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production. United States: N. p., 2007. Web. doi:10.1126/science.1137016.
Himmel, M. E., Ding, S. Y., Johnson, D. K., Adney, W. S., Nimlos, M. R., Brady, J. W., & Foust, T. D. Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production. United States. doi:10.1126/science.1137016.
Himmel, M. E., Ding, S. Y., Johnson, D. K., Adney, W. S., Nimlos, M. R., Brady, J. W., and Foust, T. D. Fri . "Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production". United States. doi:10.1126/science.1137016.
title = {Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production},
author = {Himmel, M. E. and Ding, S. Y. and Johnson, D. K. and Adney, W. S. and Nimlos, M. R. and Brady, J. W. and Foust, T. D.},
abstractNote = {No abstract prepared.},
doi = {10.1126/science.1137016},
journal = {Science},
number = 9 February 2007,
volume = 315,
place = {United States},
year = {Fri Feb 09 00:00:00 EST 2007},
month = {Fri Feb 09 00:00:00 EST 2007}
  • The mission of BioEnergy Sciences Center is to understand and overcome the recalcitrance of biomass to conversion by modifying plant cell walls with improved biocatalysts. The papers in this volume are from the plant transformation and the biomass characterization areas, and showcase the multidisciplinary and multi-institutional nature of the center. The challenge of converting cellulosic biomass to accessible sugars is the dominant obstacle to cost-effective production of biofuels in sustained quantities capable of impacting U.S. consumption of fossil transportation fuels. This was affirmed in a Biomass to Biofuels Workshop report, 'Breaking the Barriers to Cellulosic Ethanol' (DOE/SC-0095, 2006). The potentialmore » beneficial economic impact of addressing the difficulty of accessing biomass sugars was explained by Lynd et al. [1]. The BioEnergy Science Center (BESC) research project addresses this challenge with an unprecedented interdisciplinary effort focused on overcoming the recalcitrance of biomass. The 5-year mission of BESC is to make revolutionary advances in understanding and overcoming the recalcitrance of biomass to conversion into sugars, making it feasible to displace imported petroleum with ethanol and other fuels. BESC will combine plant cell walls engineered to reduce recalcitrance with new biocatalysts to improve deconstruction. These breakthroughs will be realized with a systems biology approach and new high-throughput analytical and computational technologies to achieve: (1) targeted modification of plant cell walls to reduce their recalcitrance (using Populus and switchgrass as high-impact bioenergy feedstocks), thereby, decreasing or eliminating the need for costly chemical pretreatment; and (2) consolidated bioprocessing, which involves the use of a single microorganism or microbial consortium to overcome biomass recalcitrance through single-step conversion of biomass to biofuels. We will greatly enhance our understanding of cell wall structure during synthesis and conversion. The data published will be made available through a Web portal to the bioenergy research community. As can be seen in this volume of early papers, this is a multidisciplinary and multi-institutional project which began in the fall of 2007. In forming the BESC, leading researchers from institutions across the United States were recruited to establish a distributed team that brings an unprecedented breadth and depth of expertise to the challenge of biomass recalcitrance. More details on BESC can be found at The papers in this volume primarily are from the plant transformation and the biomass characterization areas within the center. Since BESC is pursuing targeted modification of plant cell walls to reduce or eliminate pretreatment and to decrease recalcitrance, these papers show the variety of techniques that can be applied at both the plant (e.g., genetic transformation) and analytical levels. The collective goal is the understanding of cell wall biosynthesis at the molecular level and how cell wall structure and architecture influence recalcitrance. For this purpose, there is insufficient knowledge about how cellulose and hemicelluloses are synthesized, distributed within cell walls, and attached to each other, to lignin, or to cell wall proteins. We are utilizing molecular, genetic, genomic, biochemical, chemical, and bioinformatics tools to understand cell wall biosynthesis in Populus and switchgrass. We chose switchgrass and Populus as realistic potential biofeedstocks and as representatives of herbaceous and woody perennial plants. While an ultimate goal is the development of optimal biofuel feedstocks for conversion, productivity, and sustainability, our immediate goal is to prove that controlled modification of plant cell walls will reduce their recalcitrance, decreasing or even eliminating the need for costly chemical pretreatment.« less
  • A major obstacle, and perhaps the most important economic barrier to the effective use of plant biomass for the production of fuels, chemicals, and bioproducts, is our current lack of knowledge of how to efficiently and effectively deconstruct wall polymers for their subsequent use as feedstocks. Plants represent the most desired source of renewable energy and hydrocarbons because they fix CO 2, making their use carbon neutral. Their biomass structure, however, is a barrier to deconstruction, and this is often referred to as recalcitrance. Members of the bacterial genus Caldicellulosiruptor have the ability to grow on unpretreated plant biomass andmore » thus provide an assay for plant deconstruction and biomass recalcitrance. Using recently developed genetic tools for manipulation of these bacteria, a deletion of a gene cluster encoding enzymes for pectin degradation was constructed, and the resulting mutant was reduced in its ability to grow on both dicot and grass biomass, but not on soluble sugars. The plant biomass from three phylogenetically diverse plants, Arabidopsis (a herbaceous dicot), switchgrass (a monocot grass), and poplar (a woody dicot), was used in these analyses. These biomass types have cell walls that are significantly different from each other in both structure and composition. While pectin is a relatively minor component of the grass and woody dicot substrates, the reduced growth of the mutant on all three biomass types provides direct evidence that pectin plays an important role in biomass recalcitrance. Glycome profiling of the plant material remaining after growth of the mutant on Arabidopsis biomass compared to the wild-type revealed differences in the rhamnogalacturonan I, homogalacturonan, arabinogalactan, and xylan profiles. In contrast, only minor differences were observed in the glycome profiles of the switchgrass and poplar biomass. In conclusion, the combination of microbial digestion and plant biomass analysis provides a new and important platform to identify plant wall structures whose presence reduces the ability of microbes to deconstruct plant walls and to identify enzymes that specifically deconstruct those structures.« less
  • Background: Agave species can grow well in semi-arid marginal agricultural lands around the world. Selected Agave species are used largely for alcoholic beverage production in Mexico. There are expanding research efforts to use the plentiful residues (bagasse) for ethanol production as the beverage manufacturing process only uses the juice from the central core of mature plants. Here we investigate the potential of over a dozen Agave species, including three from cold semi-arid regions of the United States, to produce biofuels using the whole plant. Results: Ethanol was readily produced by Saccharomyces cerevisiae from hydrolysate of ten whole Agaves with themore » use of a proper blend of biomass degrading enzymes that overcomes toxicity of most of the species tested. Unlike yeast fermentations, Clostridium beijerinckii produced butanol plus acetone from nine species tested. Butyric acid, a precursor of butanol, was also present due to incomplete conversion during the screening process. Since Agave contains high levels of free and poly-fructose which are readily destroyed by acidic pretreatment, a two step process was used developed to depolymerized poly-fructose while maintaining its fermentability. The hydrolysate from before and after dilute acid processing was used in C. beijerinckii acetone and butanol fermentations with selected Agave species. Conclusions: Results have shown Agave s potential to be a source of fermentable sugars beyond the existing beverage species to now include species previously unfermentable by yeast, including cold tolerant lines. This development may stimulate development of Agave as a dedicated feedstock for biofuels in semi-arid regions throughout the globe.« less