Tuesday, April 20, 2010
LL Conference Facility (Hilton Clearwater Beach)
Several degradation products have been identified and quantified in AFEX pretreated corn stover using LC-MS and GC-MS techniques. They are broadly classified into four families: a) carboxylic acids, b) amides, c) furans and d) aldehydes. Some of these degradation products are known to be inhibitory to Saccharomyces cerevisiae 424A(LNH-ST) growth, particularly affecting xylose metabolism. Consequently, this fact will have detrimental effects on the economics of the process, by lowering the final ethanol yield and concentration. In this work, AFEX treated corn stover hydrolysate was separated in to several fractions based on their molecular weight using size exclusion chromatography. The effect of each fraction on fermentation of formulated pure sugar media was evaluated. Fractions which were found to cause major inhibitory effects on xylose consumption were identified and chemically characterized by mass spectrometry. The impact of the identified degradation products (at various concentrations) on glucose and xylose co-fermentation will be tested individually and in combinations. The aggregate and synergistic aspects of the inhibition and the impact of this inhibition on the kinetics of fermentation will be shown. With the help of this work we can identify several inhibitory compounds formed during AFEX pretreatment, that inhibit xylose fermentation. We believe that this information will be helpful for the molecular biologists to strengthen the xylose fermentation pathway.