Sorghum to Ethanol Research Initiative: Cooperative Research and Development Final Report, CRADA Number CRD-08-291 Page: 4 of 8
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sorghum can achieve more than 1,300 gallons of ethanol per acre given the correct genetics and
environment. In summary, sorghum may be a compelling dedicated bioenergy crop that could help
provide a portion of the feedstocks required to produce renewable domestic transportation fuels.
Summary of Research Results:
Work on this project was performed in a number of different areas: compositional analysis & Near-
infrared (NIR) model development, laboratory-scale pretreatment, enzymatic hydrolysis, and
fermentation, pilot-scale pretreatment, enzymatic hydrolysis, and fermentation, techno-economic
analysis, and education and outreach. These are summarized below.
Compositional Analysis & NIR Model Development
The goals of this portion of this work were (1) to better understand the compositional variability in
sorghum and (2) to develop a high-throughput method to determine the composition of large numbers
of sorghum cultivars. Such a tool would be very valuable for researchers in this area.
All sorghum samples were provided by the National Sorghum Producers (Lubbock, TX) and Texas A&M
University (TAM U, College Station, TX). Over 100 different sorghum varieties were analyzed, including
commercially-available cultivars and experimental lines. All analytical methods followed standard NREL
Laboratory Analytical Procedures (LAPs), available at
www.nrel.gov/biomass/analytical procedures.html, and are based on the classical dietary fiber
methods. In summary, all feedstock samples were subjected to a multi-step analytical procedure
involving two-stage solvent extraction of the samples followed by two-stage acid hydrolysis of the
extracted biomass. The structural carbohydrates were measured as their monomeric forms in the
analytical hydrolyzate. We also measured lignin (both acid soluble and acid-insoluble), and ash. Recent
work has reviewed the history' and the typical uncertainties2 of these methods.
One significant modification to the standard methods was made because of the presence of starch in
several samples. As mentioned above, structural carbohydrates are hydrolyzed to their monomers and
measured. All glucose present in the analytical hydrolyzate is apportioned to structural glucan. Typically,
glucan and cellulose are used interchangeably. However, any starch present in the material will be also
hydrolyzed to glucose, along with any native cellulose. That is, the methods we used cannot distinguish
between structural starch and cellulose; both are hydrolyzed to glucose. We noticed that a number of
samples had atypically high glucan values, which indicated the presence of starch. We measured the
starch present using the standard amyloglucosidase/a-amylase method3. Thus, three related values are
reported: structural starch, glucan, and cellulose. The glucan value is the sum of the structural starch
and cellulose values; both the cellulose and starch fractions can be converted to ethanol (albeit with
very different chemical transformation pathways).
1 "Compositional Analysis of Lignocellulosic Feedstocks. 1. Review and Description of Methods", Justin B. Sluiter, Raymond O.
Ruiz, Christopher J. Scarlata, Amie D. Sluiter and David W. Templeton, Journal ofAgricultural and Food C hemistry
2010 58 (16), pp 9043-9053.
2 "Compositional Analysis of Lignocellulosic Feedstocks. 2. Method Uncertainties", David W. Templeton, Christopher J.
Scarlata, Justin B. Sluiter and Edward J. Wolfrum, Journal ofAgricultural and Food Chemistry 2010 58 (16), pp 9054-9062.
3 Total Starch Assay Procedure(Amlyoglucosidese/a-amylase method) AOAC Method 996.11, AACC Method 76.13, available at
www.megazyem.com/downloads/data/K-TSTA.pdf2
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Wolfrum, E. Sorghum to Ethanol Research Initiative: Cooperative Research and Development Final Report, CRADA Number CRD-08-291, report, October 1, 2011; Golden, Colorado. (https://digital.library.unt.edu/ark:/67531/metadc838222/m1/4/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.