Coupling alkaline pre-extraction with alkaline-oxidative post-treatment of corn stover to enhance enzymatic hydrolysis and fermentability

Tongjun Liu, Daniel L. Williams, Sivakumar Pattathil, Muyang Li, Michael G. Hahn, David B. Hodge

Research output: Contribution to journalArticle

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Abstract

Background: A two-stage chemical pretreatment of corn stover is investigated comprising an NaOH pre-extraction followed by an alkaline hydrogen peroxide (AHP) post-treatment. We propose that conventional one-stage AHP pretreatment can be improved using alkaline pre-extraction, which requires significantly less H2O2 and NaOH. To better understand the potential of this approach, this study investigates several components of this process including alkaline pre-extraction, alkaline and alkaline-oxidative post-treatment, fermentation, and the composition of alkali extracts. Results: Mild NaOH pre-extraction of corn stover uses less than 0.1 g NaOH per g corn stover at 80°C. The resulting substrates were highly digestible by cellulolytic enzymes at relatively low enzyme loadings and had a strong susceptibility to drying-induced hydrolysis yield losses. Alkaline pre-extraction was highly selective for lignin removal over xylan removal; xylan removal was relatively minimal (∼20%). During alkaline pre-extraction, up to 0.10 g of alkali was consumed per g of corn stover. AHP post-treatment at low oxidant loading (25 mg H2O2 per g pre-extracted biomass) increased glucose hydrolysis yields by 5%, which approached near-theoretical yields. ELISA screening of alkali pre-extraction liquors and the AHP post-treatment liquors demonstrated that xyloglucan and β-glucans likely remained tightly bound in the biomass whereas the majority of the soluble polymeric xylans were glucurono (arabino) xylans and potentially homoxylans. Pectic polysaccharides were depleted in the AHP post-treatment liquor relative to the alkaline pre-extraction liquor. Because the already-low inhibitor content was further decreased in the alkaline pre-extraction, the hydrolysates generated by this two-stage pretreatment were highly fermentable by Saccharomyces cerevisiae strains that were metabolically engineered and evolved for xylose fermentation. Conclusions: This work demonstrates that this two-stage pretreatment process is well suited for converting lignocellulose to fermentable sugars and biofuels, such as ethanol. This approach achieved high enzymatic sugars yields from pretreated corn stover using substantially lower oxidant loadings than have been reported previously in the literature. This pretreatment approach allows for many possible process configurations involving novel alkali recovery approaches and novel uses of alkaline pre-extraction liquors. Further work is required to identify the most economical configuration, including process designs using techno-economic analysis and investigating processing strategies that economize water use.

LanguageEnglish (US)
Article number48
JournalBiotechnology for Biofuels
Volume7
Issue number1
DOIs
StatePublished - Apr 3 2014

Profile

Enzymatic hydrolysis
Xylans
Hydrogen Peroxide
Zea mays
Alkalies
hydrolysis
Hydrolysis
maize
Hydrogen peroxide
hydrogen peroxide
Oxidants
Biomass
Fermentation
Therapeutics
beta-Glucans
Biofuels
Lignin
Xylose
Enzymes
oxidant

Keywords

  • Alkaline pretreatment
  • Oxidative delignification
  • Xylose fermentation

ASJC Scopus subject areas

  • Energy(all)
  • Management, Monitoring, Policy and Law
  • Biotechnology
  • Renewable Energy, Sustainability and the Environment
  • Applied Microbiology and Biotechnology

Cite this

Coupling alkaline pre-extraction with alkaline-oxidative post-treatment of corn stover to enhance enzymatic hydrolysis and fermentability. / Liu, Tongjun; Williams, Daniel L.; Pattathil, Sivakumar; Li, Muyang; Hahn, Michael G.; Hodge, David B.

In: Biotechnology for Biofuels, Vol. 7, No. 1, 48, 03.04.2014.

Research output: Contribution to journalArticle

Liu, Tongjun ; Williams, Daniel L. ; Pattathil, Sivakumar ; Li, Muyang ; Hahn, Michael G. ; Hodge, David B./ Coupling alkaline pre-extraction with alkaline-oxidative post-treatment of corn stover to enhance enzymatic hydrolysis and fermentability. In: Biotechnology for Biofuels. 2014 ; Vol. 7, No. 1.
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