Pretreatment of Softwood by Acid-Catalyzed Steam Explosion Followed by Alkali Extraction

Daniel Schell, Quang Nguyen, Melvin Tucker, Brian Boynton

Research output: Contribution to journalArticlepeer-review

32 Scopus Citations


A process for Converting lignocellulosic biomass to ethanol hydrolyzes the hemicellulosic fraction to soluble sugars (i.e., pretreatment), followed by acid- or enzyme-catalyzed hydrolysis of the cellulosic fraction. Enzymatic hydrolysis may be improved by using an alkali to extract a fraction of the lignir from the pretreated material. The removal of the lignin may increase the accessibility of the cellulose to enzymatic attack, and thus improve overall economics of the process, if the alkali-treated material can still be effectively converted to ethanol. Pretreated Douglas fir produced by a sulfuric-acid-catalyzed steam explosion was treated with NaOH, NH4OH, and lime to extract some of the lignin. The treated material, along with an untreated control sample, was tested by an enzymatic-digestion procedure, and converted to ethanol by simultaneous saccharification and fermentation using a glucose-fermenting yeast. NaOH was most effective at removing lignin (removed 29%) followed by NH4OH and lime. However, the susceptibility of the treated material to enzymatic digestion was lower than the control and decreased with increasing lignin removal. Ethanol production was similar for the control and NaOH-treated material, and lower for NH4OH- and lime- treated material.

Original languageAmerican English
Pages (from-to)17-24
Number of pages8
JournalApplied Biochemistry and Biotechnology - Part A Enzyme Engineering and Biotechnology
StatePublished - 1998

NREL Publication Number

  • NREL/JA-580-22863


  • Alkali
  • Cellulose hydrolysis
  • Ethanol
  • Lignin extraction
  • Lignocellulosic biomass


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