Sunday, May 4, 2008
3-68
pH and Buffer Effects on Xylose Degradation Rates and Products
Yulin Lu, Laboratory of Renewable Resources Engineering, Purdue University, 500 Central Dr, West Lafayette, IN 47907 and Nathan S. Mosier, LORRE/Ag. and Bio. Engineering, Purdue University, Potter Engineering Center, 500 Central Drive, West Lafayette, IN 47907.
The degradation reaction routes of glucose and fructose under hydrothermal acidic conditions have been studied extensively; in contrast, xylose degradation has received less extensive study under similar conditions. In this study, we investigated the aqueous pH (0.5 – 7.0) impact on xylose degradation, and determined the kinetics of xylose disappearance rates at different pH conditions. The initial buffer system employed in this study was the McIlvaine buffer consisting of phosphate salt and citric acids (except for pH 0.5 – 1.5 buffers, where HCl/NaCl system was employed). It was observed that at pH 2.2, the xylose degradation rate was minimized (e.g. xylose disappearance rate at pH 4.2 is 9-times higher, and at pH 7.0 complete xylose disappearance occurred in 5-min reaction). In addition, the degradation reaction path changed from simple dehydration product (furfural) formation at lower pH range (0.5 – 3.0), to multiple complex liquid and polymerized products formation at higher pH range (4.5 – 7.0). In order to test the effect of buffering salt (phosphate, etc.), experiments at pH 1.0 with equivalent amount phosphate produced identical results to the same condition without phosphate addition. Therefore, the proton concentration in the aqueous solution may be the main controlling factor to which xylose degradation reactions occur. The degree of proton availability in the solution and potential protonation of the sugar –OH groups were analyzed to determine how the pH affects reaction path direction and products formation.
See more of Poster Session One
See more of General Submissions
See more of The 30th Symposium on Biotechnology for Fuels and Chemicals (May 4 -- 7, 2008)
See more of General Submissions
See more of The 30th Symposium on Biotechnology for Fuels and Chemicals (May 4 -- 7, 2008)