(211b) High Yield Ethanol Production From Fermentation of C5 and C6 Biomass Sugars by Using Native Yeast

Bioconversion of lignocellulosic feedstocks to fuel-grade ethanol is a promising route towards reduced dependence on fossil fuels and the mitigation of greenhouse gas production. Baker's yeast (Saccharomyces cerevisiae) used for industrial-scale ethanol production is unable to utilize xylose, which accounts for about 30% of the total sugars released from biomass hydrolyzates to make ethanol. Current methods to overcome this limitation focus on the development of different types of genetically modified organisms (GMOs). However, several problems exist for these GMOs. First, the consumption rate of xylose is low, and the time required to produce ethanol is relatively long. In addition, the genetic stability of GMOs, costs for propagation, and robustness under industrial fermentation conditions are as yet unreported.

Alternatively, in this research, a non-GMO approach is proposed. Simultaneous-isomerization of xylose to xylulose and reactive-extraction of xylulose to an organic phase is used for high yield conversion and concentration of the xylulose. Recovery of xylulose to an aqueous phase and fermentation to ethanol is then efficiently accomplished by native yeast. The kinetics of glucose and xylulose utilization and yield of ethanol are presented for this fermentation system.