title: Activation of lignocellulosic biomass for higher sugar yields using aqueous ionic liquid at low severity process conditions.
abstract: BACKGROUND
  Concerns around greenhouse gas emissions necessitate the development of sustainable processes for the production of chemicals, materials, and fuels from alternative renewable sources. The lignocellulosic plant cell walls are one of the most abundant sources of carbon for renewable bioenergy production. Certain ionic liquids (ILs) are very effective at disrupting the plant cell walls of lignocellulose, and generate a substrate that is effectively hydrolyzed into fermentable sugars. Conventional ILs are relatively expensive in terms of purchase price, and the most effective imidazolium-based ILs also require energy intensive processing conditions (>140 °C, 3 h) to release >90 % fermentable sugar yields after saccharification.
  
  
  RESULTS
  We have developed a highly effective pretreatment technology utilizing the relatively inexpensive IL comprised tetrabutylammonium [TBA](+) and hydroxide [OH](-) ions that generate high glucose yields (~95 %) after pretreatment at very mild processing conditions (50 °C). The efficiency of [TBA][OH] pretreatment of lignocellulose was further studied by analyzing chemical composition, powder X-ray diffraction for cellulose structure, NMR and SEC for lignin dissolution/depolymerization, and glycome profiling for cell wall modifications. Glycome profiling experiments and computational results indicate that removal of the noncellulosic polysaccharides occurs due to the ionic mobility of [TBA][OH] and is the key factor in determining pretreatment efficiency. Process modeling and energy demand analysis suggests that this [TBA][OH] pretreatment could potentially reduce the energy required in the pretreatment unit operation by more than 75 %.
  
  
  CONCLUSIONS
  By leveraging the benefits of ILs that are effective at very mild processing conditions, such as [TBA][OH], lignocellulosic biomass can be pretreated at similar efficiency as top performing conventional ILs, such as 1-ethyl-3-methylimidazolium acetate [C2C1Im][OAc], but at much lower temperatures, and with less than half the IL normally required to be effective. [TBA][OH] IL is more reactive in terms of ionic mobility which extends removal of lignin and noncellulosic components of biomass at the lower temperature pretreatment. This approach to biomass pretreatment at lower temperatures could be transformative in the affordability and energy efficiency of lignocellulosic biorefineries.
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608 USA ; Sandia National Laboratories, Biological and Engineering Sciences Center, Livermore, CA USA.
authors.forename: Ramakrishnan
authors.initials: R
authors.lastname: Parthasarathi
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608 USA ; Sandia National Laboratories, Biological and Engineering Sciences Center, Livermore, CA USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608 USA ; Sandia National Laboratories, Biological and Engineering Sciences Center, Livermore, CA USA.
authors.forename: Tanmoy
authors.initials: T
authors.lastname: Dutta
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608 USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Sun
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602 USA ; Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN 37831 USA.
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Pattathil
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608 USA.
authors.forename: N V S N
authors.initials: NV
authors.lastname: Murthy Konda
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602 USA ; Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN 37831 USA.
authors.forename: Angelo Gabriel
authors.initials: AG
authors.lastname: Peralta
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608 USA ; Sandia National Laboratories, Biological and Engineering Sciences Center, Livermore, CA USA.
authors.forename: Blake A
authors.initials: BA
authors.lastname: Simmons
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608 USA ; Sandia National Laboratories, Biological and Engineering Sciences Center, Livermore, CA USA.
authors.forename: Seema
authors.initials: S
authors.lastname: Singh
keywords: Aqueous ionic liquid; Biofuels; Higher sugar yield; Low severity condition; Pretreatment