title: Development of Agave as a dedicated biomass source: production of biofuels from whole plants.
abstract: 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 the use of a proper blend of biomass degrading enzymes including inulinase that overcomes inhibition of most of the species tested. As an example, US grown Agave neomexicana produced 119 ± 11 mg ethanol/g biomass. Unlike yeast fermentations, Clostridium beijerinckii produced n-butanol plus acetone from all species tested. Butyric acid, a precursor of n-butanol, was also present due to incomplete conversion during the screening process. Since Agave contains high levels of free and polyfructose which are readily destroyed by acidic pretreatment, a two-step procedure was developed to depolymerize polyfructose while maintaining its fermentability. The hydrolysate from before and after dilute acid processing was used in C. beijerinckii fermentations with selected Agave species with A. neomexicana producing 144 ± 4 mg fermentation products/g biomass.
  
  
  CONCLUSIONS
  Results showed Agave's potential to be a source of fermentable sugars beyond the existing beverage species to now include many species previously unfermentable by yeast, including cold-tolerant lines. This development should stimulate development of Agave as a dedicated feedstock for biofuels in semi-arid regions throughout the globe.
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Rd., PO Box 2008, Oak Ridge, TN 37831 USA ; White Cliff Biosystems Co., 528 Pointe Vista Dr., Rockwood, TN 37854 USA.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Mielenz
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Rd., PO Box 2008, Oak Ridge, TN 37831 USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: Rodriguez
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Rd., PO Box 2008, Oak Ridge, TN 37831 USA.
authors.forename: Olivia A
authors.initials: OA
authors.lastname: Thompson
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Rd., PO Box 2008, Oak Ridge, TN 37831 USA.
authors.forename: Xiaohan
authors.initials: X
authors.lastname: Yang
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Rd., PO Box 2008, Oak Ridge, TN 37831 USA.
authors.forename: Hengfu
authors.initials: H
authors.lastname: Yin
keywords: Butyric acid; Clostridium beijerinckii; Dedicated feedstock; Ethanol; Fermentation; Inulinase; Poly-fructose; Semi-arid; n-Butanol