title: Organosolv pretreatment of sorghum bagasse using a low concentration of hydrophobic solvents such as 1-butanol or 1-pentanol.
abstract: BACKGROUND
  The primary components of lignocellulosic biomass such as sorghum bagasse are cellulose, hemicellulose, and lignin. Each component can be utilized as a sustainable resource for producing biofuels and bio-based products. However, due to their complicated structures, fractionation of lignocellulosic biomass components is required. Organosolv pretreatment is an attractive method for this purpose. However, as organosolv pretreatment uses high concentrations of organic solvents (>50 %), decreasing the concentration necessary for fractionation would help reduce processing costs. In this study, we sought to identify organic solvents capable of efficiently fractionating sorghum bagasse components at low concentrations.
  
  
  RESULTS
  Five alcohols (ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-pentanol) were used for organosolv pretreatment of sorghum bagasse at a concentration of 12.5 %. Sulfuric acid (1 %) was used as a catalyst. With 1-butanol and 1-pentanol, three fractions (black liquor, liquid fraction containing xylose, and cellulose-enriched solid fraction) were obtained after pretreatment. Two-dimensional nuclear magnetic resonance analysis revealed that the lignin aromatic components of raw sorghum bagasse were concentrated in the black liquor fraction, although the major lignin side-chain (β-O-4 linkage) was lost. Pretreatment with 1-butanol or 1-pentanol effectively removed p-coumarate, some guaiacyl, and syringyl. Compared with using no solvent, pretreatment with 1-butanol or 1-pentanol resulted in two-fold greater ethanol production from the solid fraction by Saccharomyces cerevisiae.
  
  
  CONCLUSIONS
  Our results revealed that a low concentration (12.5 %) of a highly hydrophobic solvent such as 1-butanol or 1-pentanol can be used to separate the black liquor from the solid and liquid fractions. The efficient delignification and visible separation of the lignin-rich fraction possible with this method simplify the fractionation of sorghum bagasse.
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Hyogo Kobe, 657-8501 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Teramura
authors.affiliation: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodaicho, Nada-ku, Hyogo Kobe, 657-8501 Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Sasaki
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Hyogo Kobe, 657-8501 Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Oshima
authors.affiliation: Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Osaka Suita, 565-0871 Japan ; RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Kanagawa Yokohama, 230-0045 Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Matsuda
authors.affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Kanagawa Yokohama, 230-0045 Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Okamoto
authors.affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Kanagawa Yokohama, 230-0045 Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Shirai
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Hyogo Kobe, 657-8501 Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Kawaguchi
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Hyogo Kobe, 657-8501 Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ogino
authors.affiliation: Bioscience and Biotechnology Center, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Ko
authors.initials: K
authors.lastname: Hirano
authors.affiliation: Bioscience and Biotechnology Center, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sazuka
authors.affiliation: Bioscience and Biotechnology Center, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Hidemi
authors.initials: H
authors.lastname: Kitano
authors.affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Kanagawa Yokohama, 230-0045 Japan ; Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehirocho, Tsurumi-ku, Yokohama, 230-0045 Japan ; Graduate School of Bioagricultural Sciences and School of Agricultural Sciences, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Kikuchi
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Hyogo Kobe, 657-8501 Japan ; RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Kanagawa Yokohama, 230-0045 Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
keywords: 1-butanol; 1-pentanol; Fractionation; Lignin; Organosolv pretreatment; Sorghum bagasse
references.citation: J Agric Food Chem. 2011 Aug 24;59(16):8691-701
references.pmid: 21749036
references.citation: Biotechnol Prog. 2007 Nov-Dec;23(6):1333-9
references.pmid: 17973399
references.citation: Org Biomol Chem. 2010 Feb 7;8(3):576-91
references.pmid: 20090974
references.citation: Biotechnol Biofuels. 2013 Aug 01;6(1):110
references.pmid: 23902789
references.citation: Plant Biotechnol J. 2015 Aug;13(6):821-32
references.pmid: 25580543
references.citation: J Ind Microbiol Biotechnol. 2011 Jul;38(7):803-7
references.pmid: 20803247
references.citation: Sci Rep. 2014 Aug 01;4:5925
references.pmid: 25081019
references.citation: Biotechnol Adv. 2012 Jul-Aug;30(4):817-58
references.pmid: 22306168
references.citation: Bioresour Technol. 2013 Sep;144:467-76
references.pmid: 23899571
references.citation: Anal Chem. 2013 Sep 17;85(18):8857-65
references.pmid: 24010724
references.citation: Bioresour Technol. 2013 Aug;142:428-35
references.pmid: 23748091
references.citation: PLoS One. 2015 Jun 17;10 (6):e0128417
references.pmid: 26083431
references.citation: Bioresour Technol. 2002 May;83(1):1-11
references.pmid: 12058826
references.citation: Bioresour Technol. 2010 Jul;101(13):4851-61
references.pmid: 20042329
references.citation: Bioresour Technol. 2013 May;135:58-66
references.pmid: 23186666
references.citation: Biotechnol Bioeng. 2006 Aug 5;94(5):851-61
references.pmid: 16523526
references.citation: Appl Microbiol Biotechnol. 2009 Apr;82(5):815-27
references.pmid: 19214499
references.citation: Chem Rev. 2006 Sep;106(9):4044-98
references.pmid: 16967928
references.citation: Bioresour Technol. 2010 Jul;101(13):4889-94
references.pmid: 20022241
references.citation: Bioresour Technol. 2016 Jan;199:21-33
references.pmid: 26343573
references.citation: Int J Biol Macromol. 2014 May;66:57-65
references.pmid: 24530642
references.citation: Biotechnol Adv. 2015 Nov 15;33(7):1403-11
references.pmid: 26070720
references.citation: Bioresour Technol. 2012 Jun;114:389-98
references.pmid: 22446052
references.citation: Bioresour Technol. 2012 Mar;108:128-33
references.pmid: 22265982
references.citation: Int J Mol Sci. 2008 Sep;9(9):1621-51
references.pmid: 19325822
references.citation: Biosci Biotechnol Biochem. 2011;75(8):1603-5
references.pmid: 21821938
references.citation: Yeast. 1998 Jan 30;14(2):115-32
references.pmid: 9483801
references.citation: Bioresour Technol. 2005 Apr;96(6):673-86
references.pmid: 15588770
references.citation: Biotechnol Biofuels. 2013 Apr 26;6(1):45
references.pmid: 23622232
references.citation: Nat Protoc. 2012 Sep;7(9):1579-89
references.pmid: 22864199
references.citation: Chem Rev. 2010 Jun 9;110(6):3552-99
references.pmid: 20218547