Novel renewable ionic liquids as highly effective solvents for pretreatment of rice straw biomass by selective removal of lignin

Authors

  • Xue-Dan Hou,

    1. State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; telephone: +86-20-2223-6669; fax: +86-20-2223-6669 (N.L.); telephone: +86-20-8711-1452; fax: +86-20-2223-6669 (M.-H.Z.)
    2. College of Bioscience and Bioengineering, South China University of Technology, Guangzhou, China
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  • Thomas J. Smith,

    1. Biomedical Research Centre, Sheffield Hallam University, Sheffield, UK
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  • Ning Li,

    Corresponding author
    1. State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; telephone: +86-20-2223-6669; fax: +86-20-2223-6669 (N.L.); telephone: +86-20-8711-1452; fax: +86-20-2223-6669 (M.-H.Z.)
    • State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; telephone: +86-20-2223-6669; fax: +86-20-2223-6669 (N.L.); telephone: +86-20-8711-1452; fax: +86-20-2223-6669 (M.-H.Z.)
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  • Min-Hua Zong

    Corresponding author
    1. State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; telephone: +86-20-2223-6669; fax: +86-20-2223-6669 (N.L.); telephone: +86-20-8711-1452; fax: +86-20-2223-6669 (M.-H.Z.)
    • State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; telephone: +86-20-2223-6669; fax: +86-20-2223-6669 (N.L.); telephone: +86-20-8711-1452; fax: +86-20-2223-6669 (M.-H.Z.)
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Abstract

Cholinium amino acids ionic liquids ([Ch][AA] ILs), a novel type of bio-ILs that can easily be prepared from renewable biomaterials, were investigated for pretreatment of rice straw by selective extraction of lignin from this abundant lignocellulosic biomass material. Of the eight ILs examined, most were demonstrated to be excellent pretreatment solvents. Upon pretreatment using these ILs, the initial saccharification rates of rice straw residues were substantially improved as well as the extent to which polysaccharides could be digested (>90% for cellulose and >60% for xylan). Enzymatic hydrolysis of pretreated rice straw by Trichoderma reesei cellulase/xylanase furnished glucose and xylose with the yields in excess of 80% and 30%, respectively. Detailed spectroscopic characterization showed that the enhancement of polysaccharides degestibility derived mainly from delignification rather than changes in cellulose crystallinity. The yields of fermentable reducing sugars were significantly improved after individual optimization of pretreatment temperature and duration. With [Ch][Lys] as the solvent, the sugar yields of 84.0% for glucose and 42.1% for xylose were achieved after pretreatment at 90°C for 5 h. The IL [Ch][Lys] showed excellent reusability across five successive batches in pretreatment of rice straw. These bio-ILs performed as well as or better than previously investigated non-renewable ILs, and thus present a new and environmentally friendly way to pretreat lignocellulose for production of fermentable sugars and total utilization of the biomass. Biotechnol. Bioeng. 2012; 109: 2484–2493. © 2012 Wiley Periodicals, Inc.

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