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Two-step delignification of miscanthus to enhance enzymatic hydrolysis: Aqueous ammonia followed by sodium hydroxide and oxidants

  • Author(s): Liu, Z
  • Padmanabhan, S
  • Cheng, K
  • Xie, H
  • Gokhale, A
  • Afzal, W
  • Na, H
  • Pauly, M
  • Bell, AT
  • Prausnitz, JM
  • et al.

Published Web Location

https://doi.org/10.1021/ef401317z
Abstract

Pretreatment of miscanthus is essential for enzymatic production of sugars to yield bioethanol. A two-step process using 10 wt % aqueous ammonia in the first step is followed by 1 wt % sodium hydroxide (with or without oxygen or 1 wt % hydrogen peroxide) in the second step. The first step retains about 90% of the cellulose and about 67% of the hemicellulose in the solid while removing about 62% of the lignin. Both steps together achieve 83-90% delignification. Subsequent enzymatic conversion to fermentable sugars is close to 90% after 96 h. While an oxidant does not significantly increase delignification, it has a favorable effect on saccharification of the recovered solid. Infrared spectroscopy, X-ray diffraction, and two-dimensional nuclear magnetic resonance spectroscopy provide data concerning the chemical composition of the recovered solid. Inclusion of an oxidant to the pretreatment breaks β-O-4′- linked aryl ether bonds of the remaining lignin in the recovered solid. © 2013 American Chemical Society.

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