Sunday, May 4, 2008
3-27

Factors affecting lignin/protein measurements in dilute sulfuric acid treated herbaceous feedstocks

Rui Katahira, David W. Templeton, Daniel J. Schell, and Mark F. Davis. National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401

The Klason lignin method is one of the most popular methods for measuring lignin content in biomass materials. We used the Klason method to measure lignin content in herbaceous materials before and after dilute sulfuric acid pretreatment and measured more lignin in the treated material than could be accounted for in the untreated material. This phenomenon was investigated with using a combination of 13C cross polarization/magic-angle spinning (CP/MAS) solid state NMR spectroscopy and lignin removal using acid chlorite bleaching to identify possible interfering compounds in the treated material’s lignin including residual carbohydrates and protein. 13C CP/MAS spectra of acid insoluble residues (AIR) from pretreated corn stover were compared with those from the residues which remain after additional acid chlorite bleaching treatment of the AIR. Only minimal contamination due to carbohydrate and protein was observed in the acid insoluble residues. We are currently investigating the incorporation of degradation products from sugars present in the extractives using a combination of 13C CP/MAS spectroscopy and 13C-labeled sugars such as fructose, xylose and glucose. Our results indicate that degradation products derived from fructose are present in the insoluble Klason residue and may be intimately associated with the lignin. These results indicate that sugars in extractives may be rapidly degraded and then re-polymerized during pretreatment.


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