Enzymatic digestibility and pretreatment degradation products of AFEX-treated hardwoods (populus nigra)

Venkatesh Balan, Leonardo Da Costa Sousa, Shishir P.S. Chundawat, Derek Marshall, Lekh N. Sharma, C. Kevin Chambliss, Bruce E. Dale

Research output: Contribution to journalArticlepeer-review

107 Scopus citations


There is a growing need to find alternatives to crude oil as the primary feed stock for the chemicals and fuel industry and ethanol has been demonstrated to be a viable alternative. Among the various feed stocks for producing ethanol, poplar (Populus nigra × Populus maximowiczii) is considered to have great potential as a biorefinery feedstock in the United States, due to their widespread availability and good productivity in several parts of the country. We have optimized AFEX pretreatment conditions (180°C, 2:1 ammonia to biomass loading, 233% moisture, 30 minutes residence time) and by using various combinations of enzymes (commercical celluloses and xylanases) to achieve high glucan and xylan conversion (93 and 65%, respectively). We have also identified and quantified several important degradation products formed during AFEX using liquid chromatography followed by mass spectrometry (LC-MS/MS). As a part of degradation product analysis, we have also quantified oligosaccharides in the AFEX water wash extracts by acid hydrolysis. It is interesting to note that corn stover (C4 grass) can be pretreated effectively using mild AFEX pretreatment conditions, while on the other hand hardwood poplar requires much harsher AFEX conditions to obtain equivalent sugar yields upon enzymatic hydrolysis. Comparing corn stover and poplar, we conclude that pretreatment severity and enzymatic hydrolysis efficiency are dictated to a large extent by lignin carbohydrate complexes and arabinoxylan cross-linkages for AFEX.

Original languageEnglish (US)
Pages (from-to)365-375
Number of pages11
JournalBiotechnology Progress
Issue number2
StatePublished - Mar 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biotechnology


  • AFEX pretreatment
  • Corn stover
  • Enzymatic hydrolysis
  • Lignocellulose
  • Poplar

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