Tuesday, April 20, 2010
8-33

Development of alternative methods for determining acid soluble lignin in hydrolysates after dilute sulfuric acid pretreatment

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

Previous research has demonstrated sugar degradation products can interfere with the acid soluble lignin (ASL) measurement in the pretreatment hydrolysates and can lead to a high lignin mass balance closure (MBC). Three new UV-Vis methods and 1H and 13C liquid-state NMR methods were investigated to reduce or eliminate the influence of the degradation products and to improve the accuracy of the ASL measurement. The UV methods consisted of combinations of new absorptivity values prepared using an isolated corn stover lignin (CEL) and a steam explosion yellow poplar lignin (SEYP), a reduction step using NaBH4, and a secondary hydrolysis step. The new methods were verified by preparing hydrolysates from isolated lignins and measured 100% total lignin MBCs. However, the total lignin MBCs of corn stover and extracted corn stover were still high, 108-248%, using the newly developed methods indicating that sugar degradation products were still contributing to the mass balance. We further observed that the 1H-NMR method had difficulty estimating ASL content because of interferences from the residual water peak. On the other hand, the quantitative 13C-NMR analysis of the hydrolysate provided well-separated carbon signals. Based on the peak area of the lignin aromatic carbons, the ASL content was estimated to be 18.9 % of original lignin content in extracted corn stover. This value is less than the ASL content measured by the NREL standard UV method (26.3 %) but demonstrates that the quantitative 13C-NMR method may be used as an alternative method for determining the ASL content in acid pretreatment hydrolysates.

See more of Poster Session Two
See more of General Submissions

See more of The 32nd Symposium on Biotechnology for Fuels and Chemicals (April 19-22, 2010)