Sunday, May 4, 2008
1-16

Compositional analysis of water-soluble materials in switchgrass

Shou-Feng Chen, Richard S. Sevcik, Richard A. Mowery, and C. Kevin Chambliss. Chemistry and Biochemistry, Baylor University, One Bear Place #97348, Waco, TX 76798-7348

Any valuation of a feedstock for bioprocessing is inherently dependent upon detailed knowledge of its chemical composition.  Accepted analytical procedures for compositional analysis of biomass currently enable near-quantitative mass closure on a dry-weight basis.  However, total water- and/or ethanol-soluble materials are quantified gravimetrically and identified only as ‘extractives’.  Our group recently reported the first compositional analysis of water-soluble materials in corn stover.  Of particular significance was the discovery that fermentable sugars (primarily glucose, fructose, and sucrose) represented 30-46% of the dry weight of extractives (4-12% of the dry weight of corn stover feedstocks).  Because constituents belonging to this fraction of biomass are not typically considered in current models of bioconversion, these results have heightened interest in the composition of water-soluble materials.

In continuing work, analytical techniques developed in conjunction with our assessment of corn stover are being applied to assess the composition of water-soluble materials in four representative switchgrass samples.  To date, analytical characterization has resulted in mass closures approaching 80%, with several analyses yet to be completed.  Chemical constituents currently identified as contributing to mass closure include monomeric and oligomeric sugars, organic acids, inorganic ions, and a distribution of oligomers tentatively identified as being derived from phenolic glycosides.  Switchgrass results will be compared with previous analyses of corn stover extracts and presented in the context of their potential impact on biomass processing, feedstock storage, and future analyses of feedstock composition.


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